RU2794849C2 - Advanced systems, equipment and method for suppressing passive interference in directional drilling - Google Patents

Abstract

FIELD: communication; drilling.

SUBSTANCE: group of inventions relates to means of communication in horizontal directional drilling. A transmitter for use in combination with a system of horizontal directional drilling, containing a drill column extending from a drilling rig to a tool submerged in the ground, serving as a support for the transmitter, contains an antenna, one or more sensors for generating sensor data. An antenna driver for the electrical excitation of the antenna is designed to emit a depth signal in response to an input depth driver signal for aboveground reception for use in determining the depth of the specified instrument submerged in the ground. The antenna driver is designed for the electrical excitation of the antenna in response to the input driver data signal in order to emit at least one data signal characterizing sensor data using at least one frequency of the data signal, which is higher in frequency than that of the depth signal, for the aboveground isolation of the specified sensor data. The processor is made with the possibility of generating the specified input depth driver signal at the frequency of the depth signal and with the possibility of generating the specified input driver data signal characterizing the specified sensor data to control the transmission power of the depth signal relatively to the transmission power of the data signal, so that one receiving range of the specified depth signal corresponds to another different receiving range of the specified data signal. Options of a system of horizontal drilling, a portable device as part of the system of horizontal directional drilling are claimed.

EFFECT: increase in the efficiency of passive interference suppression during directional drilling by balancing the transmission power between the depth signal and the data signal.

43 cl, 24 dwg, 5 tbl

Description

State of the art

This application claims priority and benefits from U.S.S.N. 15/635,884, filed July 28, 2017, and incorporated herein by reference.

The present application generally relates to the field of communication with a device buried in the ground, and more specifically, to improved suppression of passive interference in a directional drilling system, apparatus for such suppression, and related methods.

The technology, often referred to as "horizontal directional drilling" (HDD), can be used to install utility lines and related equipment without having to dig a trench. A typical utility installation procedure uses a drill rig having a drill string and a drilling tool mounted at the far or underground end of the drill string. The drilling rig forces the drilling tool into the ground by applying axial force to the drill string. The drilling tool is controlled in the process of extending the drill string to form a pilot hole. After completion of the pilot hole, the distal end of the drill string is attached to a back-pull mechanism, which in turn is attached to the forward end of the utility section. The back-pull mechanism and the utility section are then pulled through the pilot hole by retracting the drill string to complete the installation of the section. In some cases, the back-pull mechanism may include a reaming tool that serves to increase the diameter of the pilot hole ahead of the utility section so that the installed utility section can have a diameter larger than the original pilot hole diameter.

The drilling tool may be steered in a well-known manner by orienting the asymmetric front surface of the drilling tool to deflect a desired direction in the ground in response to forward movement. To adjust this control, it is desirable to monitor the orientation of the drilling tool based on the readings of the sensors, where these sensors form part of an electronic module mounted on the drilling tool. The readings of these sensors, for example, may be modulated by a location signal transmitted by an electronics module for reception above ground by a portable radar or other suitable above ground device. In some systems, an electronics module may couple a carrier signal modulated by the sensor readings to a drill string and then transmit the signal to a drilling rig using the drill string as an electrical conductor. Regardless of the method of transmission of sensor data and for a particular amount of transmission power, there is a limited transmission range within which sensor data can be extracted with sufficient accuracy. This transmission range may be further limited by active interference and passive interference. Active interference is generally composed of signals from electromagnetic signal sources present in the work area and capable of drowning out the signal transmitted by the system. In contrast, passive interference serves to block or distort the transmitted signal, which can result in reduced range or, in some cases, inaccurate readings. One of the most common sources of passive interference is armature. In order to address and possibly remedy the shortcomings of the prior art, the Applicants filed a joint application for US patent no. 14/845,231 (hereinafter "application '231"), under the title "COMMUNICATION PROTOCOL IN DIRECTIONAL DRILLING SYSTEM, APPAR ATUS AND METHOD UTILIZING MULTI-BIT DATA SYMBOL TRANSMISSION), incorporated herein by reference in its entirety. This '231 application is filed to achieve significant advantages over the then known art and continues to provide such improvements, however, the present application brings to light additional advantages and improvements, especially with regard to passive interference, as will be discussed in more detail in the relevant paragraphs below.

The above examples of the situation in the prior art and the limitations associated with it should be considered only illustrative and non-exhaustive. Other limitations of the related art will become apparent to those skilled in the art upon reading the present description and examining the drawings.

Brief summary of the invention

The following embodiments and aspects of the invention are described and illustrated in conjunction with systems, tools, and methods, which are intended to be examples and illustrations without limitation. In various embodiments, one or more of the above problems have been mitigated or eliminated entirely, while other embodiments are aimed at other improvements.

In one aspect of the present invention, a transmitter and associated method is provided for use in conjunction with a horizontal directional drilling system that comprises a drill string extending from a drilling rig to a tool with a transmitter mounted on the tool, such that the extension and retraction of the drill string leads to the movement of the tool immersed in the ground through the ground during underground work. The transmitter includes an antenna and one or more sensors for generating sensor data. An antenna driver electrically drives the antenna to radiate a depth signal in response to an input depth driver signal for overhead reception for use in determining the depth of a submerged tool and to electrically drive the antenna in response to an input data driver signal to radiate at least one data signal , which characterizes sensor data using at least one data signal frequency that is higher than the depth signal frequency, for above-ground extraction of sensor data. The processor is configured to generate a depth driver input at a depth signal frequency and to generate a data driver input indicative of sensor data in a manner that controls the depth signal transmit power relative to the data signal transmit power such that one depth signal reception range is at least partially coincides with another, different data signal reception range.

According to another aspect of the present invention, an antenna driver electrically drives a transmitter antenna to emit a depth signal in response to an overhead depth driver signal to determine the depth of a submerged tool, and electrically drives the antenna to emit a data signal indicative of sensor data using at least one the frequency of the data signal, which is higher in frequency than the depth signal, for above-ground extraction of sensor data. The processor is configured to generate a depth driver signal at a depth signal frequency and to generate a data driver signal at a data signal frequency to control one depth signal reception range with respect to another, different data signal reception range.

According to still another aspect of the present invention, there is provided a system, a portable device, and an associated method, wherein a transmitter is configured to move through the ground in a certain area during a work procedure, transmitting a depth signal at a depth signal frequency selected in the depth signal frequency range below 1 kHz, in order to provide at least some resistance to passive interference, and this system and device is also subject to electromagnetic noise, which may vary within the considered area. The portable device is configured to scan multiple frequencies within the depth signal frequency range to measure the electromagnetic noise level at each of the multiple frequencies and identify the lowest measured noise frequency as a potential low noise depth signal frequency based on the measured noise.

According to a further aspect of the present invention, the portable device is part of a system in which the transmitter is configured to move through the ground in a certain area during an operating procedure, transmitting a depth signal at a depth signal frequency. The portable device includes an antenna for receiving a depth signal and generating an output signal. The receiver is configured to measure the electromagnetic noise level from the antenna output in at least two different frequency bands below 1 kHz by scanning each frequency band step by step to generate multiple noise level samples with some frequency step in each frequency band and display one or multiple potential depth signal frequencies for each frequency range based on the specified noise samples with some frequency step for the operator to select one of the several potential depth signal frequencies as the frequency to be used for the depth signal.

According to another aspect of the present invention, a system and associated method is provided in which a transmitter is configured to move through the ground in a certain area during an operating procedure while transmitting a depth signal at a frequency selected in the depth signal frequency range below 1 kHz to provide at least some resistance to passive interference, and this system and device is also affected by electromagnetic noise with frequencies below 1 kHz, which may vary within the considered area. The portable device is configured to measure the electromagnetic noise level in at least two frequency bands below 1 kHz by scanning each frequency band step by step to generate multiple noise level samples with some frequency step in each frequency band and display one or more potential signal frequencies depth for each frequency range based on specified noise samples with a frequency step for the operator to select one or more potential depth signal frequencies as the depth signal frequency to be used.

According to a further aspect of the present invention, a portable device and an associated method are provided as part of a system in which a transmitter is configured to move through the ground in a certain area during a work procedure while transmitting a depth signal at a depth signal frequency and a data stream on one or more data frequencies, which at least characterizes the orientation parameter of the transmitter. The portable device includes an antenna for receiving the depth signal and data frequencies to generate an output signal. The switchable filter section limits the antenna output in normal mode to one frequency range above a given frequency to pass depth and data flow at one or more frequencies, and limits the armature mode antenna output to a different frequency range to pass depth below a given frequency and flow data at frequencies above the set frequency. The processor is configured to switch the switchable filter section between normal mode and armature mode to extract the depth signal and data stream in accordance with the selection of normal mode and armature mode.

According to another aspect of the present invention, a system, method, and apparatus is provided wherein a transmitter is configured to move through the ground in a certain area during a work procedure while transmitting a depth signal at a selectable depth signal frequency set to any one of several spaced frequencies in the depth signal frequency range below 1 kHz in order to provide at least some resistance to passive interference, and this system and equipment is also affected by electromagnetic noise with frequencies below 1 kHz, which may vary within the considered area. The portable device is configured to scan said plurality of spaced frequencies below 1 kHz to measure the electromagnetic noise level at each of the plurality of spaced frequencies to identify at least one low noise frequency to establish the frequency of the depth signal at the transmitter to dynamically positioning the frequency of the depth signal relative to low-frequency noise.

Brief description of the drawings

Examples of options are illustrated by the corresponding drawings. The options and drawings presented herein are intended to be illustrative and not restrictive.

Fig. 1 is a schematic representation of an embodiment of an underground mining system according to the present invention.

Fig. 2 is a schematic perspective view, partly cut away, illustrating an embodiment of a transmitter according to the present invention.

Fig. 3 is a block diagram illustrating additional details about the embodiment of the transmitter shown in FIG. 2.

Fig. 4 is a block diagram illustrating the details of one embodiment of a frequency synthesizer that is part of the transmitter embodiment shown in FIG. 2 and 3.

Fig. 5a shows a schematic representation of a conversion table that can be used as the symbol depth and frequency conversion tables shown in FIG. 4.

Fig. 5b shows a schematic representation of antenna drive waveforms based on increasing frequency.

Fig. 5c shows a schematic representation of one of the transmitter ranges for use in armature mode.

Fig. 6a is a high-resolution noise power spectral density plot corresponding to an actual physical location where a power frequency of 50 Hz is used.

Fig. 6b is a schematic illustration of one embodiment of a screenshot showing an image on display screen 36 containing a bar graph illustrating the average noise level in each frequency subband for the embodiment of the transmitter bands shown in FIG. 5b.

Fig. 6c is a schematic illustration of another screenshot showing an image on the display screen 36 containing a bar graph illustrating the measured noise level during armature mode noise scanning for the embodiment of the transmitter bands shown in FIG. 5c.

Fig. 7 is a further enlargement of the subband 10 shown in FIG. 6a and shown here to facilitate discussion of the frequency domain portion of the depth signal and symbol frequencies.

Fig. 8 is a logic diagram illustrating one embodiment of a transmitter according to the present invention.

Fig. 9a is a block diagram illustrating one embodiment of the portable device shown in FIG. 1.

Fig. 9b is a graph schematically illustrating one embodiment of the normalized filter response shown in FIG. 9a, in normal mode.

Fig. 9c is a graph schematically illustrating one embodiment of the normalized filter response shown in FIG. 9a in armature mode.

Fig. 10a is an enlarged view of the frequency subband 6 shown in FIG. 6a.

Fig. 10b is a schematic illustration of one embodiment of a screenshot showing a view of subband 6 on a display screen for selection and modification of symbol frequencies, as well as other functions, by an operator in accordance with the present invention.

Fig. 11 is a further enlarged view of a portion of the subband 6 shown in FIG. 10a and 10b and shown here for the purpose of describing further details regarding symbol rate selection.

Fig. 12a is a logic diagram illustrating one embodiment of the method of operating a handheld device according to the present invention for the purpose of spectral scanning and symbol rate assignment for normal mode operation.

Fig. 12b is a logic diagram illustrating another embodiment of the method of operating the handheld device of the present invention for spectral scanning and symbol rate assignment for armature mode operation.

Fig. 12c is a logic diagram illustrating yet another embodiment of the method of operating the handheld device of the present invention for spectral scanning and symbol rate assignment for armature mode operation.

Fig. 12d is a logic diagram illustrating another alternative method of operating the handheld device of the present invention for the purpose of spectral scanning and symbol rate assignment for armature mode operation.

Fig. 12e is a logic diagram illustrating another alternative method of operating the handheld device of the present invention for the purpose of spectral scanning and symbol rate assignment for armature mode operation.

Fig. 13 is a logic diagram illustrating one embodiment of the method of operating a portable device according to the present invention for receiving a depth signal and a data signal during underground operations.

Detailed description

The following description is presented to enable even an ordinary person skilled in the art to make and use the subject matter of the present invention and is written in the context of a patent application and the requirements of such applications. Various modifications of the options described here will be readily apparent to those skilled in the art, and the general principles set forth herein may be applicable to other options. Thus, the options presented here are not intended to limit the present invention, but should follow the broadest scope consistent with the principles and features described here, including modifications and equivalents. It should be noted that the drawings are not drawn to scale and are schematic in nature to the extent considered appropriate to best illustrate the features of interest. The terminology of the description may be adopted for purposes of improving the reader's understanding of the various representations shown in the drawings and is not intended to be limiting in any way.

By way of introduction, Applicants understand that although attempts have been made in the prior art to address passive interference problems, such as those caused by the presence of armatures, there still remains a need for improvements. Applicants contend that passive interference is an ongoing problem, representing one of the most difficult challenges to overcome in the workplace in addition to active interference, and, to date, this difficulty has not been resolved to an acceptable extent by the prior art. Applicants today recognize that passive interference affects the reception of electromagnetic signals in one way when determining the depth and location of a buried transmitter, and in a completely different way this passive interference affects the extraction of a data stream from an electromagnetic signal characterizing the orientation and other parameters of a buried transmitter. . In this regard, determining the depth and location of a transmitter buried in the ground depends on the shape and level of the signal in the electromagnetic field or the electromagnetic signal induction lines. The shape of the electromagnetic field of the electromagnetic signal, however, can be distorted by the presence of electrical conductors, such as, for example, fittings. These distortions can lead to inaccurate depth and location determinations. Although these distortions can be reduced by reducing the frequency of the electromagnetic signal, Applicants are aware that such distortions have little, if any, effect on separating the data stream or data from the electromagnetic signal indicative of the orientation of a transmitter buried in the ground. In other words, data can be decoded from a higher frequency electromagnetic signal, regardless of field distortion, as long as there is sufficient signal strength to allow the received signal to be decoded. Accordingly, Applicants have proposed separating what should be considered an ultra-low depth signal frequency (e.g., at or below 1 kHz, or at or below 1.5 kHz) from the constellation of one or more data signal frequencies, such that the depth signal frequency exhibits more high immunity to passive interference than a higher frequency data signal with frequencies above any suitable threshold or cut-off frequency, such as above 1 kHz or 1.5 kHz, which is more susceptible to passive interference than the frequency of the depth signal, in terms of form of the field, but nevertheless serves to transmit the data stream, despite the additional distortion of the field in the presence of passive interference. At the same time, such low-frequency ranges tend to be ultra-noisy. Applicants solve this problem by introducing the additional ability to scan electromagnetic noise in a suitable low frequency range, such as, for example, the range from power frequency to a suitable upper frequency limit of 1 kHz or 1.5 kHz, in order to determine one or more frequencies in the low frequency range that are completely free from noise, or at least have a relatively low noise content, thereby avoiding the presence of too much noise. Applicants believe that the combination of features described above and elsewhere herein has not previously been encountered in the art, at least for the reason that the prevailing view in the art is that such ultra-low frequencies (for example, frequencies as low as 1 kHz or 1.5 kHz) are not practical depth signal frequencies due to the presence of strong active interference at such low frequencies. In other words, one of ordinary skill in the art would reject the idea of such low frequencies as it could render the system unable to receive a depth signal, and potentially even a data signal, due to the need to tolerate additional low frequency active interference in order to receive a low frequency depth signal. The present invention is said to overcome the problems of the prior art. A bit for the purposes of this application is a binary data element characterized as 1/0, +/-, and the like. A character for the purposes of this application is a data element representing one or more bits. A multi-bit character represents two or more bits. The symbol may represent any suitable type of information such as, for example, pitch data, roll data, temperature data, battery data, and synchronization data without limitation. Different multi-bit symbols represent different multi-bit data elements. For example, 16 different characters may represent a four-bit data element. Each multi-bit symbol for the purposes of the present invention is represented by its specific frequency, different from the frequency associated with any other multi-bit symbol. The symbol stream is formed by serially transmitted multi-bit symbols, so that this symbol stream can be decoded to be converted into a corresponding digital data stream, which may be binary. The character stream may be transmitted as a burst structure, so that the particular position of the character in question in the burst structure determines the type of data associated with that character.

Similar numerals may be assigned to similar objects in different drawings. Here fig. 1 illustrates one of the options for a system for underground work, generally designated pos. 10. The system includes a portable device 20 which, as shown, holds the operator above the surface 22 of the earth. The same device is shown enlarged in the inset. It should be noted that only a limited number of cables are shown within device 20 for the sake of clarity of illustration, but it will be understood that all necessary cables are present in the device and that it can be relatively easily implemented even by a person of ordinary skill in the art given the full text of this description. Device 20 includes a triaxial antenna cluster 26 for measuring three mutually orthogonally oriented magnetic flux components. One suitable antenna array for use here is described in US Pat. 6,005,532, which is a joint patent with this application and is incorporated here by reference. Details regarding the antenna variant used here will be given in the appropriate paragraph later. Antenna cluster 26 is electrically coupled to electronics section 32. The device may include a tilt sensor 34 to measure gravity angles from which flux components in a level coordinate system can be determined. A suitable tilt sensor comprises, by way of non-exhaustive example, a triaxial accelerometer.

The device 20 may further comprise a graphic display 36 and a telemetry antenna 40. The latter may transmit or receive a telemetry signal 44 for communicating with the drilling rig. It should be understood that the graphic display 36 may be a touch screen to assist the operator in selecting the various buttons presented on the screen, and/or scrolling between the various buttons presented on the screen may be arranged to facilitate the selection of buttons by the operator. Such a touch screen may be used alone or in combination with an input device 48 such as, for example, a start button. The latter can be used without the need for a touch screen. Moreover, various variations of the input device may be used, which may use scroll wheels and other suitable forms of selection device, either already existing and available, or as yet to be developed. The electronic section may include components such as, for example, one or more processors, some suitable type of memory, antenna drivers, and analog-to-digital converters. As is well known in the art, the latter must be able to measure a frequency that is at least twice the highest frequency of the band of interest. Other components may be added as desired, such as, for example, a magnetometer 50 to assist in positioning relative to the drilling direction, and ultrasonic transducers to measure the device's height above the ground.

As shown in FIG. 1, the system 10 further comprises a drilling rig 80 having a carriage 82 mounted to move along a pair of opposing rails 84. Attached to the opposite end of the drill string 92 is a digging tool 90. As a non-exhaustive example, the drilling tool is shown as a digging tool and is used as such as a base case for the present disclosure, however, it should be understood that any suitable earth-moving device may be used, such as, for example, a backhole reaming tool used in a backdraw operation or a matching tool. In general, the drill string 92 is made up of a plurality of releasably coupled drill pipes such that the drilling rig can forcefully drive the drill string into the ground using the string movement in the direction of arrow 94 and retract the drill string in response to movement in the opposite direction. direction. The drill pipe sections may provide a through passage for drilling mud or pressurized fluid from the drilling tool to assist cutting through the ground as well as cooling the drill bit. In general, the drilling fluid also serves to suspend and cut the surface along the outer length of the drill string. Control here can be done in a well-known manner by orienting the asymmetric surface 96 of the drilling tool to deflect in the desired direction in the ground in response to pushing the string forward, which may be referred to as "push mode". The result of turning or rotating 98 the drill string by the drilling rig will generally move the drilling tool forward or in a straight line, which may also be referred to as a "rotation" mode or a "advance" mode.

The drilling operation may be controlled by an operator (not shown) from a control console 100, which itself includes a telemetry transceiver 102 connected to a telemetry antenna 104, a display screen 106, an input device such as a keyboard 110, and a processor circuit 112 that may include suitable interfaces and a storage device, as well as one or more processors. Several control levers 114, for example, control movement of the carriage 82. The telemetry transceiver 104 may transmit or receive a telemetry signal 116 to facilitate two-way communication with the portable device 20. In one embodiment, the screen 106 may be a touch screen such that the keyboard 110 may be in this case only an option.

In one embodiment, the device 20 may be configured to receive an electromagnetic depth signal 120 and an electromagnetic data signal 122 transmitted from a transmitter 130 installed inside a drilling tool or other tool that is sunk into the ground. These signals may herein be collectively referred to as transmitter signals. The transmitter signals may be dipole signals. It should be understood that the portable device may operate in a mobile locator mode as shown in FIG. 1, or in a stationary mode, when this portable device is installed on the ground, for example, as shown in joint US patent no. 9,540,879, which is incorporated here by reference. Although the present invention illustrates a dipole location field transmitted from a drilling tool and rotating about the axis of symmetry of this field, the present invention should not be considered limited in this regard.

The information conveyed by the data signal may include, but is not limited to, attitude parameters based on pitch and roll sensors, temperature values, pressure values, battery status, tension sensor readings in the context of a pullback operation, and other such parameters. Device 20 receives transmitter signals using antenna array 26 and processes the received data signal 122 to extract data from it, as will be described later.

In FIG. 2 is a schematic perspective view, partially cut away, illustrating one embodiment of transmitter 130. The latter includes a main body that may be at least generally cylindrical in configuration. A battery compartment 138 may be provided at one end of the case, while a main printed circuit board (PCB) 144 may be mounted at the opposite end 140, which may itself support a transmitter antenna 148. An accelerometer module 150 may be located near one end of the PCB 144. Other sensors and components may be located on the main PCB as described below.

Referring now to the block diagram shown in Fig. 3 in combination with FIG. 2 for the purpose of describing additional details regarding one embodiment of transmitter 130. This transmitter includes a processing section 152 that receives information from sensors through a multiplexer 154. This multiplexer 154 may be interfaced with any number of sensors forming a sensor array. In the present example, the array of these sensors comprises accelerometers 158, which are installed in the accelerometer module 150 shown in FIG. 2, a pressure sensor 160 that can be used to measure pressure in the annulus in the well around the transmitter, a temperature sensor 164, a battery current meter 168, and a battery voltage sensor 170. External communication for the transmitter may be provided, in some embodiments, external connection 174 connection. Such communication signals do not need to be transmitted through the ground, instead, it can be carried out when the transmitter is above the ground, for example, in a position near the device 20. External communication can be implemented by any suitable method, including, but not limited to, IrDA infrared communication. , NFC, WiFi, Zigbee or Bluetooth near field communication. Section 178 of the power supply may contain a battery 180, which supplies power through the detector 184 overvoltage and reverse polarity. This detector supplies power to the logic and sensor power supply 188 and to the antenna driver power supply 190 . The logic and sensor power supply supplies power to the sensor array as well as to the processor section 152. The antenna driver power supply supplies power to depth signal antenna driver 194 and data signal antenna driver 198, which electrically drive opposite ends of the antenna coil, component part of antenna 148. Drivers 194 and 198 may alternatively be half-bridge drivers. The antenna drivers receive input signals from the processor 200, which is part of the processor section. This processing section further comprises an oscillator 210 such as, for example, a crystal oscillator. This oscillator may be selected to provide a relatively high degree of thermal stability and overall stability. The processor (CPU) 200 includes a timer section 212 that can serve to generate a reference signal whose stability reflects the stability of the oscillator 210. The timer output frequency is selected based on a reset timer value that can be set by the user. The processor is in communication communication with memory 218, which may contain any suitable information, including, but not limited to, depth signal frequency information 224 and symbol rate information 228, each of which will be described at the appropriate time later.

In FIG. 4, a diagram of one of the options for a frequency synthesizer is shown, indicated as pos. 300 and implemented as part of the processor section 152 shown in FIG. 3. It should be understood that the frequency synthesizer may be implemented in the form of hardware, software, or some suitable combination of hardware and software. The frequency synthesizer may be some suitable option, either already existing and available at the moment, or one that has yet to be developed. The variant shown in Fig. 4 is a two-channel direct digital synthesizer (DDS) having a depth channel 304 and a symbol channel 308. The depth channel provides its output signal 310 to the depth signal driver 194 shown in FIG. 3 to generate the depth signal 120, while the symbol channel sends its output signal 312 to the data signal driver 198 shown in FIG. 3 to generate data signal 122 (FIGS. 1 and 2). Each of the depth channel waveform lookup tables section 320 and the symbol channel waveform lookup table section 324 each contains at least one waveform or phase lookup table that characterizes one period of the selected waveform, such as, for example, sinusoid. Alternatively, each of these sections, the depth channel lookup table section and the symbol channel lookup table section, may contain multiple waveform or phase lookup tables. In this example, there is one conversion table of the waveform, shown schematically and marked pos. 326, in each of the lookup table sections, a section for a depth channel and a section for a symbol channel. It should be understood that any desired waveform can be characterized by its lookup table. Further, the depth channel mapping table(s) and the symbol channel mapping table(s) are not required to characterize the same waveform(s). In some versions of the frequency synthesizer, there are no requirements for a conversion table. For example, a suitable mathematical expression may be used.

In FIG. 5a is a graphical illustration of a lookup table 326 that may contain a large number of characterizable waveform value samples based on, for example, available storage space and desired resolution. Assuming that in this embodiment the depth channel and the symbol channel use the same lookup table, it should be understood that in this case only a single copy needs to be kept for access from both channels. In this embodiment, lookup table 326 represents one cycle of a sine waveform. The vertical axis represents the proportion of Pulse Width Modulation (PWM), where a positive signal peak corresponds to a 100% level, and a negative signal peak corresponds to a 0% level, for reasons that will be described later. The horizontal axis of the graph represents time intervals (slots), where each particular time slot has an amplitude associated with it. The timeslot values can be considered as samples that are selectively addressed by the depth channel phase accumulator 330 and the symbol channel phase accumulator 334, respectively, using an "m" wide address structure. It should be noted that a large number of samples can be associated with the conversion table under consideration. Each phase accumulator is configured to provide an output sample to the lookup table section based on an input increment or shift amount determined by depth channel frequency control module 338 and symbol channel frequency control module 340, respectively. Each phase accumulator generates what can be called a quantized sawtooth output signal that changes from one level or sample to the next by the corresponding amount of input gain. In response to each incoming sample from the corresponding phase accumulator, either from the depth channel or from the symbol channel, the conversion table 326 sequentially generates a digital output value received by the oscillator 350 with a pulse-width modulator (PWM) in the channel of the depth and the generator 352 with a pulse-width modulator (PWM) in a symbolic channel, respectively, in an "n" wide address configuration. Based on the digital value received by each PWM generator, the pulse width modulator generates an output train of pulses having at least a substantially constant output amplitude, but the duration (width) of such a pulse increases in proportion to the output value from the conversion table. Filtering, due to the inductive properties of the antenna 148, smoothes the waveform to approximate the desired output waveform, such as a sinusoidal waveform, for example.

In the diagram shown in Fig. 4, each of the depth channel output 360 and the symbol channel output 362 can be generated, for example, over the entire frequency range from a frequency close to 0 Hz to 45 kHz with a high degree of accuracy. It should be understood that any suitable frequency range can be used here, and that the range from 0 to 45 kHz is given here only as an example, so it should not be considered exhaustive. In the example shown, the error can be no worse than about +/- 0.1 Hz or less, with a resolution no worse than about 5 Hz. It should be noted that the specified accuracy, in the context of the considered option, is given for a frequency of at least about 45 kHz, which represents the lower limit of accuracy in the frequency range. Compared to prior art approaches, it should be understood that the present invention provides higher accuracy, improved consistency, and marked flexibility in terms of frequency selection over the entire transmission range. The frequencies of the output signals 360 and 362 are set based on the amount of input increment applied to the depth channel phase accumulator 330 via the depth channel frequency control module 338 and to the symbol channel phase accumulator 334 via the symbol channel frequency control module 340 . The depth channel frequency control module 338 receives a depth signal frequency input signal 368 indicative of the frequency of the depth signal. The depth channel frequency control module may convert the given depth signal frequency into an increment value for the depth channel phase accumulator 330 in any suitable manner. In one embodiment, the depth channel frequency control module may include an increment lookup table 370 that maps the depth signal frequency to the increment value. Alternatively, the following formula can be used to determine the amount of increment:

Here, the size of the phase accumulator is chosen to provide the minimum required frequency resolution, and the update rate of the phase accumulator is set by the timer 212 (FIG. 3). Similarly, the symbol channel rate control module may convert a given symbol rate received at data symbol stream input 374 into an increment value for symbol channel phase accumulator 334 in some suitable manner, such as, for example, by using increment conversion table 370 or a formula. The source from which the data symbol stream is input to the data symbol stream input 374 will be described at the appropriate time in the following. It should be noted that there is no requirement for the depth channel frequency and symbol channel frequency control modules to necessarily use identical increment conversion tables. Tab. 1 below illustrates a portion of one embodiment of increment conversion table 370.

Table 1 Relationship between desired output frequency and phase accumulator size increment

Desired output frequency
(Hz) Phase accumulator increment
(counts) 5 1 50 10 500 100 32770 '6554 45000 9000

Based on Table 1, it should be understood that it provides a high degree of resolution in terms of the frequency selected for each of the signals - the frequency of the output signal 360 of the depth channel and the frequency of the output signal 362 of the symbol channel. In this embodiment, a resolution of 5 Hz can be implemented over the entire frequency range, from the industrial frequency of AC power networks around the world to 45 kHz. Of course, other options may use a similar or different resolution even at even higher frequencies. Other resolutions can be used, some of which are coarser and some even finer. Applicants believe that 5 Hz is a relatively small common multiple of 50 Hz and 60 Hz, which are the most common power frequencies around the world. Further discussion of issues related to power frequency will be given below.

Continuing to look at FIG. 4, it should be understood that the frequency of the depth channel output 360 and the frequency of the symbol channel output 362 are shown as frequency tones that are of limited or fixed duration, at least substantially fixed frequency, and may be of variable amplitude. In this regard, primary amplitude control may be based on a multiplier that may be set by a multiplier table 376 available for reference by both depth channel frequency control module 338 and symbol channel frequency control module 340. This multiplier is defined in the range of 0 up to 1.0. To obtain the desired transmit power at the particular frequency under consideration, the samples obtained from the lookup table 326 are multiplied by this factor. Thus, a multiplier of 1.0 gives maximum or 100% amplitude, while a multiplier of zero gives zero output. As will be described later, a multiplier table can be used to compensate for changes in coupling between the antenna and driver circuits, as well as changes in antenna impedance in response to changing frequency.

Here again, only one copy of the multiplier table will need to be kept if the same table is used for both channels. Further, magnitude/amplitude shaping may be performed using a depth channel shape/amplitude control module 380, which may be referred to as a depth channel shaper, and using a symbol channel signal shape/amplitude control module 382, which may be referred to as a symbol channel shaper. In another example, the output of depth channel PWM signal generator 350 is a continuous depth signal 386 that is at least substantially continuous in magnitude. In this case, the depth channelizer may not be needed, although its operation should be understood to reflect that of the symbolic channelizer as described herein. It should be understood that the depth of the transmitter can be determined, based on the depth signal 386, using well-known dipole equations as described, for example, in US patent no, 5,633,589, which is incorporated here by reference. In another example, the output signal 390 of the symbol channel PWM signal generator 352 illustrates a sequence of output symbols 392a-392f whose frequency may vary from one symbol to the next. As will be described below, the output signal 390 may comprise a stream of symbols. In this example, there is no gap of zero between adjacent symbols, which would have been present between them originally or would have been inserted by the phase accumulator 334 . Thus, the frequency may change abruptly from one symbol to the next, such that it may cause noise due to the frequency jumps. It should be understood that the symbols 392a-392f are generated in such a way as to avoid frequency spikes by having these symbols start and end at an approximately zero value. Such shaping may be implemented by applying a suitable notching or tapering function by symbol channel generator 382 such as, for example, a Hamming window, a Harm window, a Welch window, or a triangular window, among others. The common property of all these clipping functions is that they all have a value of zero at any point outside the window interval, so that each symbol starts and ends with a signal value of zero.

Let us now turn to FIG. 5b and table 2 in combination with FIG. 2, 4 and 5a. Although there is no such requirement, various embodiments of transmitter 130 may be configured to transmit depth signal 120 and data signal 122 using a number of transmitter bands, generally denoted ref. 400 and extending from about 0 to 45 kHz as shown in FIG. 5b. It should be understood that other transmitter bands and subbands may be used in other embodiments, so that the present embodiment is a non-exhaustive example. Although a zero value is indicated as a lower limit, it should be understood that the actual lower limit may be represented by the world's dominant power frequencies or some higher value. The transmitter bands are designated BT1-BT5 and are also listed in Table 2. Although the description structure applied in FIG. 5b and Table 2 uses transmitter bands that contain frequency subbands, it should be understood that this band/subband nomenclature may change in any suitable manner, for example, as long as the necessary correspondence is maintained with the last column of Table 2, which contains the table 376 multipliers. It should be noted that the multiplier values in the multiplier table 376 in the illustrated embodiment are constantly increasing from one subband to the next, which is also reflected by the successively increasing values of the subband signals 402a-402j in FIG. 5b. Alternatively, each subband signal 402a-402j may be represented by a separate lookup table to create a set of lookup tables, instead of using a multiplier table with a single lookup table. Alternatively, it is not necessary to define frequency bands or subbands since the multiplier can be specified, for example, as a function. As noted above, there is no requirement to use a lookup table. For example, one embodiment may use an expression in the form of a function that is linear and that can give a substantially continuous change in the value of the multiplier as the transmit frequencies are resolved at the transmitter. Another function may be derived, for example, using a suitable curve fitting method such as, for example, the least squares method.

Table 2. Bands and subbands of the transmitter

transmitter range frequency range Subrange number Frequency subrange Multiplier Tab. 376 BT1 0-4.5 kHz SB1 0 - 4.5 kHz 0.34 BT2 4.5 kHz- 9 kHz SB2 4.5 kHz - 9 kHz 0.45 BT3 9 kHz-18 kHz SB3 9 kHz - 13.5 kHz 0.55 SB4 13.5 kHz - 18 kHz 0.63 BT4 18 kHz-31.5 kHz SB5 18 kHz - 22.5 kHz 0.70 SB6 22.5 kHz - 27 kHz 0.75 SB 7 27 kHz - 31.5 kHz 0.82 BT5 31.5 kHz-45 kHz SB8 31.5 kHz - 36 kHz 0.86 SB9
sb10 36 kHz - 40.5 kHz 0.92 40.5 kHz - 45 kHz 1.00

Continuing to look at FIG. 5b, the frequency range from 0 to 45 kHz is further subdivided into 10 sub-bands SB1-SB10, each with a width of 4.5 kHz, according to the present embodiment. Each frequency range above the BT1 band and subband above the frequency of subband 1 can be considered to also contain its own lower bound. The use of transmitter bands, although not a requirement, allows control over transmission efficiency as well as transmission power. Although each of the transmitter bands BT1 and BT2 contains only one subband each, it should be noted that the transmitter band BT3 contains two subbands, SB3 and SB4, while each of the bands BT4 and BT5 contains three subbands: SB5-SB7 and SB8-SB10, respectively. . One embodiment of the transmitter according to the present invention may be configured to transmit depth signal 120 and data signal 122 on the same subband. In another embodiment, the transmitter may be configured to transmit the depth signal 120 over a range different from the range used for the data signal 122. In this regard, it should be understood that the use of a separate synthesizer channel (FIG. 4) for the depth channel creates greater flexibility in terms of choosing the frequency of the depth signal relative to the data signal. In the case of a wideband transmitter, as will be further described below, the transmitter may transmit on two or more bands, such that the bands may even be separated by other bands.

In some embodiments, transmitter 130 may be configured to cooperate with antenna 148 such that the transmitter may transmit over a wide frequency range, or from the lowest frequency to about 45 kHz or higher. With this approach, this wide frequency range can be covered by a single broadband transmitter using a single antenna, while maintaining suitable power efficiency over the entire wide frequency range. For transmission over the entire frequency range from the lowest frequency to about 45 kHz, by way of non-exhaustive example, the variants of the multiplier table 376 may be configured to include any suitable number of values. Depth channel phase accumulator 330 and symbol channel phase accumulator 334 may be configured to use a suitable input position in the multiplier table 376 based on the frequency to be generated. In this way, it is possible to maintain at least substantially constant power consumption over the entire wide transmission range, regardless of the particular transmission frequency. In the prior art, with a constant drive voltage and waveform, the transmitter would otherwise consume more and more power as the frequency decreases. In the embodiments presented here, it is not required to excite the antenna at a resonant frequency. This resonant frequency, represented by the inductance of the antenna 148 in combination with any parasitic capacitances, is generally much higher than the highest frequency of the transmission band, such as 45 kHz, for example. For example, the resonant frequency may be in the megahertz range.

In one embodiment of a broadband transmitter, the transmitted frequency group may range from subband SB3 to subband SB 10, corresponding to a wide frequency range from 9 kHz to 45 kHz. In the context of a wideband transmitter, there is no need to limit the frequency to any one of these subbands (see, for example, Table 2).

Based on the foregoing, the present invention can provide a broadband transmitter with a single antenna excited over a wide frequency range, such that the transmitter can maintain a constant or controllable power consumption, at least to the extent that the power consumption would otherwise vary significantly over the same frequency range using a single driver waveform combined with a multiplier value. Power consumption variations over a wide frequency range can be limited to acceptably low levels from 9 kHz to 45 kHz. With this approach, Applicants have been able to create a broadband transmitter operating in a wide frequency range with stabilization and power consumption control, which has not yet been observed. In the past, underground work using different frequencies for depth signal and location data required the purchase of a separate transmitter that would be specifically tuned to each of the frequencies of interest. The innovations proposed herein can result in significant cost savings because a single broadband transmitter can replace multiple transmitters used in prior art. In this regard, the provisions of the present invention are equally applicable to a transmitter that transmits a depth signal or tone at one discrete frequency, and transmits a data signal at another frequency modulated in some suitable manner, such as, for example, using binary phase shift keying ( BPSK), quadrature phase shift keying (QPSK), or Manchester coding.

As discussed here, Applicants recognize that there are advantages associated with transmitting a depth or tone signal at a relatively low or ultra-low frequency, such as, for example, 1 kHz or below, and transmitting a symbol signal at one or more higher frequencies, such as, for example, frequencies in the range extending upwards from 1 kHz or higher, eg above 4.5 kHz. In one embodiment, the transmitter has a so-called "armature" mode or passive interference mode to reduce the effects of passive interference, while maintaining data throughput at data frequencies. In this sense, low frequencies or depth tones avoid sources of passive interference, such as armature, at the risk of being affected by additional low-frequency active interference in the absence of the protections proposed here, while higher frequencies at which data is transmitted are associated with higher data throughput levels based on the Nyquist frequency. Because the presence of, for example, armature can distort, weaken, and disrupt the shape of the electromagnetic location field for transmitter location, these effects can make it difficult to accurately locate a buried transmitter, which definition relies on the shape of the location field for location, as well as cause incorrect determination of depth readings, which is based on the level of the location signal. For example, a point on the ground that has been designated as directly above the transmitter may be offset from its actual position. As another example, passing under a rebar can cause a sudden increase in the displayed depth reading of a transmitter mounted on a submerged tool due to signal attenuation due to the influence of the rebar. The use of a relatively low frequency for the depth signal is advantageous in terms of avoiding such effects. Until now, the prevailing view has been that the transmission of a depth signal at the low frequencies described here, such as, for example, frequencies below 1 kHz, presents technical problems that seemed insurmountable in the known art due to the prejudice noted above that a depth signal at an ultra-low frequency would turn out to be exposed to such strong active interference as to make its use practically unacceptable. The present invention proposes to circumvent these apparent limitations using a previously unknown combination of features.

The present invention makes it possible to transmit a depth tone (tone) that is separated in frequency from the frequencies of the data signal by an amount that has not yet been observed, in particular when one antenna is used to transmit both the depth signal and the data signal. For example, a depth tone may be transmitted at or below 1 kHz, as will be explained immediately below.

Let us now turn to FIG. 5c, which is a schematic illustration of a number of transmitter bands, denoted as a whole by pos. 420, for the variant with armature mode. It should be noted that all frequency values in this drawing are given in kHz. This embodiment also contains the previously described transmitter bands BT2-BT3, which were defined in Table 2 and repeated in Table 3. In this embodiment, rebar array 424 contains a rebar low band (RBL) extending from approximately 330 Hz to 400 Hz. Hz; reinforcing mid-frequency range (rebar middle band, RBM), extended from approximately 405 Hz to 575 Hz; and a rebar high band (RBH) extending from approximately 580 Hz to 750 Hz. It should be noted that the number of armature ranges and their endpoints may vary in any suitable manner. For example, the RBH band may have an upper limit of 1 kHz, or some other value between 1 kHz and a lower limit of the BT2 band of 4.5 kHz, such as, for example, 1.5 kHz. As another example, the RBL range may have a lower limit approaching the power frequency. As yet another example, an ultra-low frequency band may be added downstream of the RBL band so that this new band may have a lower limit approaching the power frequency. As yet another example, an additional range may be inserted between the RBH and BT2 ranges. Here again, it is not necessary to take the range-by-range multiplier specification approach as long as the value of such multiplier is specified for any potential transmission frequency that may be chosen.

Reinforcing ranges 424 are shown in Table 3. The last column in Table 3 contains a multiplier table 410, which is a variant used in place of the multiplier table 376 included in Table 2 when operating in armature mode. The multiplier tables can vary in complex ways based on a variety of factors, as empirical multiplier table 410 demonstrates. Fig. 5c schematically illustrates a sinusoidal lookup table associated with multiplier table 410 and having waveforms 412a-412c corresponding to the RBL, RBM, and RBH bands. Waveforms 414a-414c correspond to subbands SB2-SB4, respectively.

Table 3. Armature mode

transmitter range frequency range Subrange number Frequency subrange Multiplier Tab. 410 RBL 330 Hz- 400 Hz n/a n/a 0.34 RBM 405 Hz- 575 Hz n/a n/a 0.39 RBH 580 Hz- 750 Hz n/a n/a 0.47 BT2 4.5 kHz- 9 kHz SB2 4.5 kHz- 9 kHz 0.45 BT3 9 kHz-18 kHz SB3 9 kHz - 13.5 kHz 0.55 SB4 13.5 kHz - 18 kHz 0.63

Table 4 illustrates examples of frequencies selected based on noise scans for armature transmitter operation. It should be noted that all data frequencies S0-S15 have been selected from subband SB4, although this is not a requirement. In this respect, said frequencies may be selected from at least the subbands SB2-SB4 shown in FIG. 5c. It should be noted that frequencies from the SB2-SB4 subbands generally provide good transmission range with relatively high data throughput or wide bandwidth. In this regard, one of the subbands may be selected based on the average noise level per subband determined during a manual noise scan, automatically, or through some combination of manual and automatic modes. At the same time, the depth signal frequency of 345 Hz provides an appreciable level of immunity to passive interference such as that caused by the presence of rebar. Given the multiplier table 410 in Table 3, the multiplier may be set to 1.0 for the highest frequencies or subband to be transmitted by a particular transmitter option. The remaining input positions in the multiplier table may be set, for example, to provide a constant power consumption based on the power distributed between the depth signal and the frequencies of the data signal, or based on the considerations of Applicants, which are set out below. In one embodiment, the values in the multiplier table for normal or armature mode can be determined empirically, for example, by adjusting the transmit power of the depth signal relative to the data signal, while observing the total power consumption of the transmitter so that the maximum power level is not exceeded. Such an empirical procedure is probably best performed in an area where active interference is weak. A particular embodiment may also take into account the depth signal reception range relative to the data signal reception range, which will be discussed further below.

Table 4. Example of frequency selection for armature mode

Designation Frequency Hz) Depth signal 345 S0 14,740 SI 14,850 S2 15.085 S3 15.210 S4 16,500 S5 16.770 S6 16.695 S7 17.105 S8 17.190 S9 17.225 S10 17.240 S11 17.335 S12 17.445 S13 17,560 S14 17.680 S15 17.995

For comparison purposes, Table 5 sets out the frequencies selected for normal mode when the depth signal frequency is above 1 kHz.

Table 5. Example of frequency selection for normal mode

Designation Frequency Hz) Depth signal 40.675 S0 40.740 S1 40,850 S2 41.085 S3 41.210 S4 41,500 S5 41.825 S6 42.235 S7 42,400 S8 42,700 S9 42.845 S10 43.205 S11 43.420 S12 43.665 S13 43.825 S14 44.360 S15 44.635

The frequencies shown in Table 5 are selected from subband 10. Applicants understand that the presence of active interference found in the noise scans that form the basis for selecting these frequencies is not relevant to the problem of passive interference. In this regard, attempts to use the depth signal frequency from Table 5 may not be feasible, leading to the need to switch to an armature mode using a much lower depth signal frequency, such as 345 kHz, for example, as seen in Table 4. Alternatively, the frequency selection for depth signal and data symbols in normal mode can be limited to the same frequency range as the frequency selection for data symbols for armature mode (SB-2 - SB-4 in the example shown in Table 3). It should be noted that in such an embodiment, the range of data signal frequencies at a particular transmit power can be at least somewhat improved in normal mode compared to the range of data signal in armature mode, at least as a result of recognizing relatively less active interference in normal mode. mode due to filtering at the input, as will be discussed later.

As a result of reading the above detailed description of the transmitters and associated components according to the present invention, details regarding the transmission of the data signal 122 will become clear. In particular, an M-level frequency shifting technique is used here, so that several different symbols can be combined in one stream as data signal 122. In armature mode, frequencies for data symbols can be selected in the range BT2 and/or BT3 to construct the data signal 122, while the frequency of the depth signal 120 can be selected in the group of armament ranges 424 (FIG. 5c), based on the noise scan, as else will be described. In normal or armature mode, the data signal can be used to carry a stream of multi-bit symbols. The ability to transmit a stream of multi-bit symbols is facilitated at least in part by the use of synthesizer 300 shown in FIG. 4. In particular, the multi-bit data symbol stream may be input 374 to the data symbol stream to symbol channel rate control module 340 . With this approach, data symbols corresponding to a wide variety of discrete frequencies can be specified as part of a data symbol stream, where each of the different symbols corresponds to a different frequency than the other symbols. In one embodiment, the data symbols in the symbol stream may correspond to 16 symbols (4 bits), although any suitable number of symbols may be used here based on the desired data throughput. Fig. 4 illustrates the output signal 390 based on 16 symbols, the frequency S0-S15, where S0 corresponds to the lowest frequency, and each of the successive consecutive symbols corresponds to a relatively higher frequency. Although not strictly required, the mapping or assignment of symbols to frequencies may be done in any suitable manner. Thus, the output 390 corresponds to the example input symbol stream S2, S12, S2, S15, S0, and S10 at input 374.

Based on the foregoing, Applicants claim that the system 10 can provide a level of active noise immunity and passive interference immunity that has not yet been achieved in underground operations, such as, for example, horizontal directional drilling and associated back-pull operations. or reverse well drilling. Pertinent considerations and other details will be given in the context of a discussion of the device 20 that receives the depth signal and the data signal, and which can also assist in identifying the depth signal frequency and symbol frequencies to be used by the transmitter. It should be understood that the symbol frequency ordering given in Table 4 is not a requirement. In Table 5, the depth signal frequency may be located between the symbol frequencies. By using a separate channel to generate the depth signal (FIG. 4), this depth signal can be located in a different subband than the subband where the symbol frequencies are. Further, the symbol frequencies may be reordered or permuted in any suitable manner. With respect to limiting frequency selection to one subband, it should be understood that one embodiment of a wideband transmitter may be configured to simulate the operation of a transmitter that is limited in capability depending on the subbands. For example, the wideband transmitter's selected frequencies may be limited to a single subband, even if the wideband transmitter is capable of transmitting over a wide band of subbands.

In FIG. 6a is a plot of the noise power spectral density measured at high resolution. The graph is indicated as a whole pos. 500 and corresponds to the actual physical location in the area where the power frequency of 50 Hz is used. Signal level is shown on the vertical axis and frequency is shown on the horizontal axis. The frequency range from 0 to 45 kHz corresponds to the frequency range covered by the set of transmitters described in accordance with the present invention. The graph also indicates the sub-bands SB 1-SB 10 of the transmitter. It is interesting to note that subband 1 turned out to be very noisy compared to the noise level observed in most of the higher frequency subbands. As a consequence, it can be argued that one of ordinary skill in the art would have to give up on the idea of using a depth signal below 1 kHz or 1.5 kHz for at least this reason, as will be discussed below. Applicants, however, have identified significant improvements that will allow accurate positioning of the depth signal in the region of low frequency active noise at a frequency that can even be below 1 kHz.

Although the spectral scan result shown in FIG. 6a illustrates spectral information at essentially one location, it should be understood that such spectral information can be collected cumulatively. For example, a spectral scan may be performed while an operator is walking along a planned well path with device 20, which is measuring characteristics of the noise environment at this time. With this approach, it can be considered that the spectral plot shown in Fig. 6a represents the noise environment along the entire planned well path, and the subsequent frequency selection should be based on the noise environment that has been characterized along the entire length of the planned well path, while still using the frequency selection methods described here.

Fig. 6b illustrates one version of a screenshot showing the display screen 36, which is a bar graph illustrating the average noise level in each subband when operating in normal mode, where the SB-10 subband is highlighted, for example, using hatching and/or color, or whatever - in any other suitable way to indicate that this SB-10 subrange has been automatically selected. Alternatively, the locator may provide automatic recommendations based on the average noise level in the subband in combination with other statistical characteristics. As such suitable statistics, for example, standard deviation, noise floor and peak noise level can be used. In yet another embodiment, more than one subrange may be recommended, in which case the user may choose between the recommended subranges. The recommendation of multiple subranges may be based on the limited amount of statistical variation between subranges. For example, both subbands 9 and 10 can be recommended based on the relatively limited difference between the two subbands, as seen in FIG. 6b. As another example, multiple subbands may be recommended simultaneously based, for example, that the average noise level in the first subband is lower than the average noise level in the second subband, while the peak noise level in the first subband is higher than the peak noise level in the second subband. In one embodiment, where more than one subband is recommended, the system may be configured to allow the user to select one of several subbands recommended to him for transmission. Alternatively, the user may select multiple recommended subbands to transmit. In yet another embodiment, one or more of such multiple recommended subbands may be automatically selected for transmission. Since the information presented in Fig. 6a is based on a high resolution noise scan using a 5 Hz frequency step, a significant amount of noise information can be extracted from these data. For example, the standard deviation of the noise values in each subband can be determined. The heights of the various bars in Fig. 6b may be weighted by adding or subtracting some value based on one or more other statistical parameters. For example, if the standard deviation for a particular band is large, which means a relatively wider spread of noise values in that subband, the associated bar height can be maintained or even increased by some amount. On the other hand, if the standard deviation for a particular range is small, which means that the noise values within that subrange are relatively consistent, the height of the bar associated with that subrange in FIG. 6b can be reduced. Similarly, bar heights within a bar chart may be weighted based on the peak noise level, so that the bar height for each subband having a high peak noise level may be increased by some amount. In any case, the weighting can be done based on threshold values for the relevant statistics. The weighting may be based on individual statistics or combinations of statistics. The automatic subband selection can be accepted by the operator by touching the Auto-Select button 780 or by touching any band the operator wishes to select. The operator can override automatic selection, for example, based on which specific transmitters are currently available for underground operations. As another reason to present to the operator, other statistics may be shown to him. For example, dashes 781 located above the bars (the number of which is assigned individually) show the peak noise levels in the respective subbands. An operator may decide not to use a subband that has a particularly high peak noise level, even if the average noise level in that subband is relatively low. To override the automatic selection, the operator can touch the Manual Select button 782 and then touch the subband he wants to select. Alternatively, the locator display 36 may display a graph, bar graph, or some other suitable form of noise representation derived from the spectral scan results shown in FIG. 6a so that the operator is then able to manually select one of the subbands, for example by touching the selected subband on the display screen. In yet another embodiment, the locator 20 may allow the operator to initially enter information regarding available transmitters to allow automatic selection of a subband covered by one of these transmitters while excluding unavailable subbands in a manner consistent with US Patent no. 8,729,901, which is a joint patent with this application and is hereby incorporated by reference in its entirety. Fig. 6b shows the subbands that were unavailable due to the unavailability of transmitters using dashed lines. In contrast, solid lines indicate the available subranges. In this example, subbands SB-1 and SB-5 to SB-7 are not available. In one embodiment, subranges may be excluded based on regulatory constraints. With this approach, the portable device itself and the operator are not allowed to make frequency selections that would violate the regulations in force in a particular jurisdiction. Such frequency limits may be specified by the manufacturer on a regional basis. In one embodiment, handheld device 20 or some other system components, such as, for example, drilling rig 80, may be equipped with a GPS receiver that can locate underground operations and then view local frequency requirements.

Continuing to look at FIG. 6b, the display screen shown here may remain "live" at least until the frequency selection procedure is completed. In other words, it is possible to monitor and display the average noise level for each subband under consideration, either individually or weighted using other statistical parameters, in real time so that the operator can monitor. With this approach, the operator can move the locator while observing the average noise level in different subbands. For example, an operator may walk along a planned well path and monitor for noise along the path before proceeding with drilling. With this approach, subbands that are particularly noisy at one or more points along the path can be avoided. If the operator decides, he can move the locator to some other location, such as along the path, and initiate a rescan of the noise across the entire bandwidth by selecting the rescan button 784. As discussed above, the noise environment may be characterized based on reception using one or more antennas. The operator can change the receive mode using button 786. For example, in one of the receive modes, the bar graph shown in FIG. 6b may be represented based on reception along a single axis, such as the X-axis, for example. In another reception mode, a bar graph may be represented based on a vector sum generated along three orthogonal reception axes. Button 786 may also be used to initiate armature mode and/or switch between armature and normal modes. In this case, the display screen 36 may change, as will be seen at the appropriate time in the future. When the operator changes receive modes, the rescan button 784 may initiate a new noise scan and present noise values based on the selected receive mode. The operator can switch between different noise scanning modes as desired. In one embodiment, the noise scan that forms the basis for the display screen shown in FIG. 6b may be a high resolution scan. In combination with noise scanning, a number of optimized low noise frequencies can be automatically selected based on the desired number of symbol frequencies. For example, in each subband, select sixteen symbol frequencies and a depth signal frequency. In one embodiment, during the real-time presentation of noise on the screen shown in FIG. 6b, the noise level in each subband may be represented as the average of the noise values measured at each of the selected frequencies within each subband. It should be noted that selecting the rescan button 784 causes a new or updated selection of frequencies in each subband. Locator 20 may be configured to store sets of selected frequencies associated with various measurement locations, such as in memory 714 shown in FIG. 9a. Accordingly, the selected frequency sets are optimized for each measurement location so that different selected frequency sets can be used at different times during operation. The term "optimized" should mean that frequencies are chosen to avoid interference based on one or more statistical parameters such as, for example, average noise level, standard deviation, and peak noise level. The selected frequency sets may be communicated to a transmitter, for example, over the ground using the external communications connection 174 shown in FIG. 3. The buried transmitter may be commanded in any suitable manner to switch to another set of selected frequencies during underground operations. For example, the command to switch between valve and normal modes may be given based on a predetermined drillstring rotation sequence, or by transmitting an electromagnetic signal from an above-ground device to be received by transmitter 130, which would then be configured as a transceiver. Some embodiments may use a drill string as an electrical conductor, or may use a well-known wire-in-tube design so that data can be transferred between a buried transmitter/transceiver and a drilling rig. For example, a drilling rig may send a command through the drill string to switch between rebar and normal modes. One option for initially establishing operation in either armature or normal mode is based on the orientation of the transmitter at the time of startup when the batteries are inserted. For example, one end of the transmitter may be oriented upward to establish normal mode of operation, while orienting the same end downward to establish armature mode.

Fig. 6c illustrates one variant of a screenshot showing a display screen 36 containing a bar graph representing noise measurements for operation in armature mode, where the SB-4 subband is highlighted, for example, using shading and/or color, or in some other suitable manner. , to indicate that this SB-4 subband has been automatically selected for data transmission purposes. At the same time, bars 790, 792, and 794 are associated with rebar ranges RBL, RBM, and RBH, respectively. In this example, the height of each bar for armature bands shows the measured active noise level for the lowest noise frequency, which may also be referred to as the potential depth signal frequency, which was found by scanning in each armband, while the bars for subbands with SB-2 over SB-4 may denote the average for the data symbol frequencies in each subband, as discussed above. Cross-hatching or some other suitable visual highlighting may indicate an automatic selection or recommendation of the lowest noise frequency in the armature bands, which in this example is the RBM band, although this is not a requirement. The operator can select, override or change the selected armature frequency, for example by touching the subband column. It should be understood that in order to generate both screens shown in FIG. 6b and 6c, one noise scan across the entire band may be used, although this is not a requirement. After such a noise scan, the display screen shown in FIG. 6c can provide a real-time indication of the noise for each of the rebar ranges so that, for example, an operator can walk along the intended drilling path while monitoring noise variations along the path. Alternatively, multiple depth signal frequencies may be transmitted. For example, a signal of a selected frequency for each of the reinforcement bands RBL, RBM, and RBH may be transmitted in slot sequence for reception over ground. It should be understood that such a set of frequencies can be selected in the normal mode, and signals with these frequencies can be transmitted in a similar way. Signal reception at depth signal frequencies will be discussed at the appropriate time later.

In FIG. 7 is a further enlargement of the subband 10 shown in FIG. 6a, where this image is indicated in general pos. 550 and is shown here to illustrate the selection of the depth signal frequency and the sixteen symbol rates S0-S15 in this subband for the normal mode. It should be noted that the choice of symbol rates for data transmission in armature mode can be made in a similar manner based on noise scanning in the available frequency band for data transmission (subbands SB-2 to SB-4 shown in Fig. 5c), while the frequency The depth reinforcement signal is selected separately from a plurality of reinforcement ranges 424, as shown in FIG. 6c. In FIG. 7, each of the selected frequencies is indicated by an arrow. Different frequencies were chosen, for example, based on their correspondence to low noise points on the noise graph. Based on the choice of frequencies, such as frequencies S0-S15, automatically and/or manually, Applicants claim that the system 10 can provide a level of noise immunity that has not yet been achievable in underground operations, such as, for example, horizontal directional drilling and associated back-pull and reverse reaming operations. It is also claimed that the reinforcing mode described here provides hitherto unseen opportunities in terms of resistance to passive interference. Relevant considerations and other details will be set forth in the context of a discussion of the device 20 that receives the depth signal and the data signal, and which also assists in identifying the depth signal frequency and symbol frequencies to be used by the transmitter.

In FIG. 8 is a logic diagram illustrating one of the options for the operation of the transmitter, designated as a whole as pos. 600 according to the present invention. It should be noted that for the purposes of this description, it will be assumed that the depth signal frequency, as well as the frequencies S0-S15 associated with the symbols, have already been selected for each, both normal and armature, mode. These selected frequencies may be stored in some suitable location such as, for example, depth signal frequency table 224 and symbol frequency table 228 shown in FIG. 3. Execution of the method begins at block 602 and proceeds to block 604 to select either the normal mode or armature mode in any suitable way. At 606, the depth multiplier is read. At step 608, the transmitter finds the frequency increment (step) of the depth signal, for example, from increment conversion table 370 (FIG. 4) as part of the depth channel frequency control module 338 operation. In one embodiment, using a single depth channel waveform conversion table, such as table 326 shown in FIG. 4, depth channel phase accumulator 330 can always refer to this single lookup table for the waveform in conjunction with calling the appropriate multiplier value from the multiplier table (eg, multiplier tables 376 or 410). On the other hand, in one embodiment using multiple depth waveform lookup tables, at step 608 the correct waveform lookup table may also be identified so that the depth channel phase accumulator 330 refers to the appropriate depth channel waveform lookup table based on frequencies. At step 610, the depth channel phase accumulator 330 starts counting based on the frequency increment of the depth signal, so that the lookup table 326 and the depth channel PWM signal generator 350 start to continuously generate a signal 386 at the depth channel frequency to emit the depth signal 120 at that frequency, according to with the multiplier value. In step 614, the CPU 200 reads the sensor information through the multiplexer 154 to collect the sensor data to be transmitted. At block 618, the CPU assembles a character stream from the sensor data, which may use a burst structure, as will be described later. This symbol stream is input 374 to the data symbol stream input 374 of the symbol channel rate control module 340, as shown in FIG. 4. At 619, the depth signal frequency multiplier(s) may be read. At 620, the symbol channel rate control module may use a lookup table 326 to identify the appropriate frequency for the current symbol to be transmitted, as well as a multiplier value (eg, multiplier table 376 or 410). On the other hand, in an embodiment using multiple symbol waveform lookup tables, it is also possible at step 620 to identify the correct waveform lookup table so that the symbol channel phase accumulator 334 refers to the corresponding symbol channel waveform lookup table. It should be understood that in order to transmit any particular symbol stream, it may be necessary for the multiplier values to switch at 620 on a symbol-by-symbol basis from one symbol to the next on a frequency basis. At block 624, the current symbol is transmitted. At block 626, the presence and availability of another symbol for transmission is checked. If a character is present and available, work returns to block 620 so that the procedure is repeated for the next character. On the other hand, if the next symbol is not yet ready, operation may proceed to block 630, which responds to a request to switch from one normal or armature mode to another, respectively armature or normal mode. This request may be transmitted in any suitable manner, such as based on a turn orientation sequence, data transmission through the drill string, or radio communications. If there is no such request, operation may return to block 610, which continues transmission of the depth signal. At step 614, the sensor data is read again and the procedure continues from that point on. On the other hand, if there is a request for a range switch, work returns to block 606 and continues from there. It should be understood that the data signal 122 is most often transmitted on a substantially continuous basis simultaneously with the depth signal 120.

With the transmitter 130 embodiments detailed above, let us now turn to FIG. 9a-9c in combination with FIG. 1 for the purpose of describing additional details regarding device 20, which may be referred to interchangeably as a locator or receiver. In FIG. 9a is a block diagram illustrating the device 20. The latter contains a battery 700 that powers a power supply 704 that supplies all the components of the device with the appropriate electrical supply voltage, denoted as V+. The electronics section 32 includes a processor 710 coupled to a memory 714. The processor-controlled telemetry section 720 is connected to the two-way communication antenna 40 via a signal 44. In some embodiments, the telemetry channel may be unidirectional from the device 20 to the drilling rig, in which case the transceiver 102 needs only in the functionality of the receiver. The external communication circuit 722 provides external communication with the transmitter using the external communication connection 174 (FIG. 3) of the transmitter. As discussed above, such communication does not require transmission through the ground, but may be carried out when the transmitter is above the ground, for example, in a position near the device 20. Such external communication may be implemented in any suitable manner, including, without limitation, systems, using IrDA, NFC, WiFi, Zigbee or Bluetooth standards. The dual-mode wideband front end 730 is configured to receive the depth signal 120 and the data signal 122 using the X, Y, and Z antennas constituting the antenna cluster 26 to measure the three orthogonal components of the considered signals, as well as to make noise measurements along these three axes, as more will be described later. Additional details regarding one of the options for the antenna cluster will be given in the appropriate place in the future. Each of the X, Y, and Z antennas is coupled to its own low noise amplifier (LNA) 734a, 734b, and 734c, respectively, where these amplifiers are all configured identically. The amplified output of each LNA is provided to a respective switchable filter section 738a, 738b, and 738c, where all three sections are configured in the same way and may be collectively referred to as filter sections 738. Each filter section includes two bandpass filters 740a and 740b having roll-off or kink in amplitude. - frequency response on the low-frequency side and a roll-off or kink in that response on the high-frequency side. Filters 740a may be referred to as normal mode filters, while filters 740b may be referred to as reinforcement mode filters. Although filters 740a and 740b are shown as individual functional blocks, it should be understood that these filters may be implemented in any suitable manner. As a non-exhaustive example, each filter may be implemented as a series of high pass and low pass RC filters distributed along the signal chain. The normalized frequency response of filter 740a for normal mode is shown schematically in plot 742 in FIG. 9b. In the normal mode version of the filter, the two high pass filters may each have a low pass corner frequency of about 4 kHz, and the four low pass filters may each have a high pass break frequency of about 90 kHz. This variant gives a relatively flat frequency response with a low frequency break 742a of about 10 kHz and a high frequency break of about 50 kHz. The roll-off slope below 10 kHz is approximately 40 dB of attenuation per decade, and the roll-off slope above 50 kHz is approximately 80 dB of attenuation per decade. Fig. 9c schematically illustrates a variant of the normalized frequency response of armature mode filter 740c, denoted pos. 744. The high frequency break frequency 743b may remain unchanged as shown, although this is not a requirement. On the other hand, the low frequency corner frequency 745 may be shifted down the frequency axis, for example, to about 180 Hz with a rolloff of about 3 dB. With this approach, there is a slight attenuation of the signal at a frequency of 300 Hz. It should be understood that the low frequency edge of the response of filters 740a and 740b can be set to take into account the fundamental harmonic of the AC mains voltage and the lower order harmonics of this voltage, which can be very strong especially in the case of an armature filter. Filter switching control line 747 is shown as a dotted line extending from CPU 710 to each of the filters in filter section 738. Accordingly, CPU 710 can control filter selection in both normal and armature modes. After each of the filters 738a-738c, a separate amplifier 750a-750c can be installed with a sufficient gain to ensure normal operation of the analog-to-digital converters (ADC (analog-to-digital converter (A / D))) 754a-754c. Each ADC 754 provides its output to CPU 710. In one embodiment, device 20 may be configured to receive the symbol stream in such a way as to suppress power frequency harmonics, since there is effectively no energy in the symbol stream at these power frequency harmonic frequencies. For example, the received signal may be processed in such a way that the receiver response is matched to the symbol spectra, as plot 553 of FIG. 7. In particular, the receiver spectral response can be matched to the transmitter spectral response by integrating the received symbol stream over a time period corresponding to the time duration or period of each symbol. With this approach, the frequency response of the receiver will be consistent with the response of the transmitter in the sense that it will have points of zero reception at the harmonic frequencies of the power frequency. Accordingly, the receiver suppresses or ignores energy at harmonic frequencies while dramatically amplifying the energy of the spectral components associated with the symbol. The receiver may use any suitable demodulation procedure that produces periodic zeros, including, but not limited to, the Discrete Fourier Transform (DFT)).

Referring to FIG. 9b and 9c, it would be useful at this point to compare the normal mode filter response 742 and armature mode filter response 744 in view of the spectral plot shown in FIG. 6a, and given the above considerations regarding strong active noise at low frequencies, below what Applicants refer to as the ultra-low frequency range of the depth signal, such as, for example, frequencies below 1 kHz. In this sense, the low frequency bend 743a of the normal mode filter characteristic is located at a frequency of approximately 4 kHz, while the low frequency bend 745 of the filter characteristic for armature mode is located at a frequency no higher than approximately 180 Hz. Although reducing the frequency of the low-frequency bend of the armature filter characteristic allows measurement of the depth signal at very low frequencies, at least up to 300 Hz or even to the corresponding power frequency, it should be understood that at the same time a serious technical problem arises. In particular, and as seen in FIG. 6a, the armature mode filter passes a large proportion of the noise between 180 Hz (or even lower) and 4 kHz that the normal mode filter normally cuts out. These noises can contain, for example, very strong power frequency harmonics. It is argued that receiving all of these noises would seem counterintuitive to one of ordinary skill in the art and could be seen as a possibility that the portable device would be unable to receive such low frequency depth signals, as well as creating additional difficulties with respect to reception of higher frequencies. Applicants are aware, however, that the combination of the teachings of the present invention allows such additional noise to be passed through to allow very low frequency depth signals to be received, while at the same time providing the ability to position the depth signal at a precise frequency in the armature range, which may be noise-free. at least to a reasonable approximation. With this approach, the depth signal can be received with some guarantee of protection from the effects of generally high levels of ambient noise at frequencies below 1 kHz, or some other suitable limit, such as, for example, 1.5 kHz. Applicants are not aware of any proposals for this combination of features in the prior art.

In accordance with FIG. 9a and with the above detailed description of the locator 20, it should be understood that this locator can be configured to perform noise measurements and analysis to select a transmitter for transmitting the depth signal and data signal, as well as to establish the frequencies that should be associated with each of these signals. Of course, band selection may not be necessary if a wideband transmitter is used. Noise measurements can be determined based on each of the orthogonal axes of antenna 26 (antennas X, Y and Z as shown in FIG. 9a). These individual noise components can be used to establish the amount of 3D noise, for example, based on the vector sum of the components from the three antennas. This vector sum can be useful because the noise readings at a particular point will be essentially invariant with respect to changes in locator orientation. On the other hand, the display presentation of noise readings obtained from one axis will generally change at an arbitrary specific point as the orientation of the locator changes. By allowing noise monitoring along one antenna axis, such as the X axis, the operator can identify which particular axis along the well path might be problematic in terms of interference. The noise values can be determined in any suitable way, such as, for example, based on the Fast Fourier Transform (FFT))). In one embodiment, a noise scan may be performed along each axis for comparison purposes. For example, for example, a signal from an axis where relatively stronger noise is noted than from other axes can be processed differently for data extraction purposes.

Let us now turn to FIG. 10a, which is an expanded view of the subband 6 shown in FIG. 6a, this view as a whole is indicated by pos. 800. For the purposes of this discussion, assume that the SB-6 subband is available and has been selected either automatically or by the operator for use in underground operations. It should be noted that symbol/data rate selection may be made for any subband in accordance with these descriptions. It is assumed that, at least initially, the operation is carried out in the normal mode. With the subband selected, the frequencies for the depth signal 120 and the data signal 122 can be set. In one embodiment, these frequencies may be predetermined, for example by the manufacturer or based on a previous noise scan, as described above. Alternatively, the display 36 may be used to present a spectral plot for the subband shown in FIG. 10a, in some suitable form, to the locator operator so that the operator can select frequencies. Fig. 10b illustrates one version of the screenshot showing the screen view of the display 36 representing the SB-6 subband, still under the assumption of the normal mode. It should be understood that the locator can perform a resizing function on the display screen 36 that uses a Zoom In button 802 and a Zoom Out button 804 so that the operator can stretch the spectrum image in the horizontal direction to make more detailed selections. frequencies. Typically, the operator can select frequencies that correspond to low noise points in the spectrum shown on the display screen. The frequency selection results may be rounded to reflect the frequency resolution of the transmitter to be used. As discussed above, embodiments of transmitters according to the present invention may have a frequency resolution of 5 Hz as a non-exhaustive example. In FIG. 10a, twenty-one points are identified that correspond to low noise, so that these points are indicated by vertical marks (a)-(u). In one embodiment, where one frequency is used for depth signal 120 and 16 symbol frequencies, seventeen of the 21 frequencies can be used. As described above, the depth signal frequency may be located anywhere within a subband, interspersed with symbol frequencies, at either end of the subband, or even in a different range. As one example, the depth signal frequency can be chosen at the point that has the lowest noise level among the identified frequencies, in this example, this is the frequency (j). In yet another embodiment, frequencies may be selected or reselected automatically by the locator 20, for example, in response to an operator pressing the Auto-Pick button 806 on the display screen 36. In one embodiment, the processor 710 may examine the spectrum shown in FIG. 6a to identify the lowest noise points until a suitable number of symbol frequencies has been accumulated. In other embodiments, the processor may perform the selection procedure based on some suitable method. For example, the lowest noise frequencies can be chosen in combination with the condition of maintaining some minimum separation between adjacent frequencies. With respect to armature mode, the frequency selection procedure may comprise a frequency selection procedure for data symbols, which may be substantially identical to those shown in FIG. 10b, and an additional procedure for selecting the depth signal frequency, for example, in a group of reinforcement ranges 424, which (selection procedure) may be based on the representation of the reinforcement ranges 424 on the display, as shown in FIG. 6c, or on a display of noise scan results for a group of rebar ranges, or some portion of those results, which may look similar to that shown in FIG. 10b, or based on what is shown in this drawing. With this approach, the operator is given considerable flexibility in choosing the frequency of the depth signal in armature mode.

Still referring to FIG. 10b, a frequency can be added, for example, by touching the Add Frequency button 808 and then touching the spectrum graph. The frequency can be deleted, for example, by touching the Delete Frequency button 810 and then touching the frequency to be deleted. The frequency can be moved, for example, by touching the Move Frequency button 812 and then touching and dragging the frequency to be moved. The selected sub-range can be changed by touching the Change Sub-range button 814 (Change Sub-range). As will be further described immediately below, frequency selection is not limited to identifying low noise points, but may also take into account high noise points or spectral scan areas.

In FIG. 11 is a further enlarged view of FIG. 10a of the spectrum region from 24 kHz to 25 kHz, indicated as a whole pos. 820 and is included here for the purpose of describing additional details regarding the frequency selection procedure. In addition to identifying points that correspond to low noise, as described with respect to FIG. 10a, processor 710 may apply what is referred to as a "keep-out region". The latter will exclude any identified low noise frequency by having a peak noise level within the selected frequency window 822 centered on said identified low noise frequency. Noise can be identified, for example, based on a magnitude above threshold 824, based on the average noise level for the subband under consideration, and/or based on the noise level associated with a nearby low noise point. In one embodiment, said frequency window may be approximately 60 Hz (+/- 30 Hz) wide and the threshold level may be 10 dB or more above the noise level at the associated low noise point. Based on the use of such a frequency window, frequencies (b) and (e) can be excluded due to the proximity of peaks 826 and 830, respectively. In the event that more frequencies are needed, processor 710 may re-examine the spectrum shown in FIG. 11 in order to identify a new group of candidate frequencies. In a group of reinforcement bands, the reinforcement frequency window may have a different width than the frequency window in normal mode. For example, the armature frequency window may be narrower since the noise can be scanned in small steps, such as 5 Hz.

In FIG. 12a is a logical diagram illustrating a variant of the method generally indicated by pos. 900 to operate the locator 20 in performing spectral scanning and assigning frequencies for subsequent normal operation in accordance with the present invention. The method starts at step 904 and proceeds to step 908, where the full frequency spectrum is scanned, for example, from 0 Hz to 45 kHz for this case, although any suitable range can be used for this scan. This scan may be a high resolution scan, for example using 5 Hz resolution as discussed above. Alternatively, a lower resolution initial scan may be used such that the resolution is only sufficient to establish the average noise level for the subband. If the subband selection procedure relies on a low resolution spectral scan, a high resolution spectral scan may subsequently be performed as part of the frequency selection procedure described below. When a broadband transmitter is to be used for underground operations, only a single high resolution scan can be used for frequency selection purposes. At 910, an average noise level value for each subband is determined. At 914, a subband may be recommended based on the obtained average noise floor values. Typically, the subband having the lowest average noise level can be recommended, although other options may use other recommendation protocols and/or automatic subband selection. For example, the subband having the lowest peak noise level may be recommended. As another example, as discussed above, more than one subrange may be recommended. At 918, the user may be prompted to enter a command on the display screen 36 whereby the user may accept the recommended subband or select a different subband. For example, a user may select a different subband based on their knowledge of transmitters available for underground operations. As discussed above, this information may serve as an initial input so that method 900 may exclude subbands not covered by the currently available transmitter(s). When a subband has been selected, the method proceeds to step 920, where the frequencies of the subband are determined. In one embodiment, the subband frequencies may be predetermined and stored in the memory 714 of the locator or in the memory 218 of the transmitter. Alternatively, the subband frequencies may be determined by the operator during operation by presenting the subband on the display screen 36 as discussed above. Alternatively, the subband frequencies may be determined automatically in accordance with the discussion with respect to FIG. 10a-10c and 11 with or without the use of a forbidden window, as applied in step 924. In the case of using a broadband transmitter for underground operations, steps 910 and 914 are not required, since the entire transmission range can be available for frequency selection without the need for frequency clipping. any particular subband(s), such that, at 920, frequencies can be allocated across the entire transmission band. Accordingly, transmission frequencies may be automatically selected over the entire available band and/or may be specifically selected by the user based on high resolution noise scan results without the need for frequency assignment restrictions based on subbands. It should be understood that the wideband transmitter option may be configured to operate, for example, based on operator preference using subbands in the same manner as subband limited transmitters where the frequency assignment may be limited to one or more subbands, although this is is not a requirement. At step 928, it is determined if a sufficient number of frequencies have been identified. If not, operation returns to block 920 to identify additional frequencies. If a sufficient number of frequencies have been identified, operation proceeds to step 930, which determines the recommended frequencies for the signal 120 depth and signal 122 data. This last step can be an option in a fully automated version. At step 934, information may be presented on the display 36 to collect user-entered commands, such as confirming the choice of frequencies or changing the choice of frequencies. For example, the user may prefer to move the depth signal frequency to a different position in their subband, or to a completely different subband. Of course, in the wideband transmitter embodiment, it is not necessary to limit the choice of frequency to any particular band and/or subband. At step 938, information about the selected frequencies can be transmitted to the transmitter 130 using an external locator communication circuit 722 and an external communication connection 174 (FIG. 3) of the transmitter. The transition to the normal mode of operation may be performed during the underground work procedure at step 940.

In one embodiment of method 900, the number of frequencies to be selected may be based on the state of the noise environment. For example, if a noise scan, whether in a limited subband or not, reveals a low noise environment, relatively more frequencies can be selected. In this case, 32 or more symbol rates may be used instead of 16 symbol rates. If the noise scan reveals a highly noisy environment, a relatively smaller number of symbol rates can be used, such as 4 or 8 symbol rates instead of 16 symbol rates, for example. Generally, using relatively fewer frequencies can help avoid various sources of noise in a noisy environment. On the other hand, using more symbol rates can increase data throughput.

In FIG. 12b is a logic diagram illustrating one of the variants of the method, generally indicated by pos. 914 to operate the locator 20 in performing spectral scanning and assigning frequencies for subsequent armature mode operation in accordance with the present invention. The method begins at step 946 and proceeds to step 948, where a full frequency spectrum scan may be performed, for example, from 0 Hz to 45 kHz for this case, although any suitable range may be used for this scan. For example, based on FIG. 5c, scanning can be performed from approximately 0 Hz to 18 kHz. This scan may be a high resolution scan using 5 Hz resolution, especially for armband group 424. Lower resolution may be used to select symbol frequencies as described above. At 950, the amount of average noise in each subband may be determined for the subbands of symbol frequencies, and the scanned frequencies may be analyzed for potential use as depth signal frequencies. The subband for the data symbols may be recommended and/or selected based on some suitable statistical parameter, such as, for example, noise average values, noise floor values, noise peak values, and/or standard deviation values, in a manner consistent with the above descriptions in conjunction with the recommendation of one or more depth signal frequencies. At 954, the display 36 may prompt a user-entered command whereby the user may accept the recommended subband or select a different subband for the data symbols. The user may also select, modify or confirm one or more potential depth signal frequencies. It should be noted that the ability to enter a command by the user may be an option in an automated variant that performs frequency selection for the user. When the data subband and depth signal frequency are selected, the method proceeds to step 956 where the data subband and depth signal frequency are set. In one embodiment, the subband for the data and frequency of the depth signals may be predetermined and stored in the memory 714 of the locator or in the memory 218 of the transmitter. Alternatively, the data subband frequencies and/or depth signal frequencies may be determined by the operator during operation by presenting these data subbands and/or reinforcement bands on the display screen 36 as discussed above. Alternatively, the subband for the data and depth signal frequency may be determined and applied automatically in accordance with the discussion above with reference to FIG. 10a-10c and 11 with or without the use of a forbidden window, as applied at step 958 and discussed above.

It should be noted that subband-based determination and indication in step 950 is not required, as discussed above, since there is no requirement to limit frequencies to any particular subband(s), and step 950 may allocate frequencies over the entire transmission band. Accordingly, transmission frequencies may be automatically selected over the entire available range and/or customized by the user based on a high resolution noise scan. It should be understood that one embodiment of a wideband transmitter may be configured to operate, for example, based on operator preference using subbands in the same manner as subband limited transmitters, where the frequency assignment may be limited to one or more subbands, although this is not a mandatory requirement. At block 960, it is determined if enough frequencies have been identified, if not, operation returns to block 950 to identify additional frequencies. If enough frequencies have been identified, operation proceeds to step 962 where frequencies are recommended for depth signal 120 and data signal 122. This last step may be an option in fully automated equipment. At step 964, information may be presented on the display screen 36 for the purpose of collecting user input for commands and data, such as confirming the choice of frequencies or changing the choice of frequencies. For example, the user may prefer to move the depth signal frequency to a different armature range position, or to a completely different armature range. Of course, in the wideband transmitter embodiment, it is not necessary to limit the choice of frequency to any particular band and/or subband. Here again, there is no mandatory requirement that the user enter commands and data into the automated equipment. At step 966, information about the selected frequencies can be transmitted to the transmitter 130 using an external locator communication circuit 722 and an external communication connection 174 (FIG. 3) of the transmitter. The transition to armature mode of operation may be performed during the underground procedure at step 968.

Turning now to FIG. 12c in combination with FIG. 12b. In FIG. 12c is a flow diagram illustrating one embodiment of the method performed at step 950 in FIG. 12b, where this scheme as a whole is indicated by pos. 970, for the purpose of analyzing the scanned frequencies in the frequency range(s) of the depth signal. The method starts at step 972 and proceeds to step 974, which compares the noise values resulting from the noise scan in each of the RBL, RBM, and RBH armature bands shown in FIG. 5c to identify, at 976, at least that frequency in each of these armature bands at which the lowest noise occurs. In this embodiment, the result is the three potential depth signal frequencies at which the weakest noise occurs. In step 978, the low noise frequency band may be presented to the user, for example, based on the screen shown in FIG. 6c, and/or automatic selection of the lowest noise frequency from that frequency group can be performed. At block 980, operation may return to block 950 shown in FIG. 12b.

Let us now turn to FIG. 12d in combination with FIG. 12b, the first of these drawings is a flow diagram illustrating another embodiment of the method carried out in step 950 of FIG. 12b, the circuit as a whole is indicated by pos. 982, for the purpose of analyzing scanned frequencies in the range(s) of depth frequencies. The implementation of the method begins at step 983 and proceeds to step 984, which compares several noise values obtained from the noise scan, for the entire armature range, with a threshold value. The latter may, at least initially, have a low value, for reasons that will become apparent from the following discussion. In step 985, low noise frequencies below a threshold are identified. At step 986, it is checked if any frequencies were identified when the low threshold was used. If frequencies have been identified, operation proceeds to block 987 where the depth signal frequency may be displayed, automatically selected, and/or confirmed in cooperation with the operator, if desired. At block 988, work returns to block 950 shown in FIG. 12b. If, on the other hand, no frequencies have been identified in step 986 because all scanned frequencies have noise levels above the noise threshold, operation proceeds to step 990 where the system may request the operator to start a noise rescan in at least the armature. range. It should be noted that the decision at step 986 is not a requirement. In this sense, any suitable response to excessive or strong active interference can be formed. For example, in another embodiment, the operator may be given an indication that there is a lot of noise in the rebar range. In this embodiment, if rescan is selected, operation proceeds to rescan at block 991, followed by return to block 985. it increase the noise threshold. If so, the noise threshold may be increased, for example, by a predetermined increment, or the user may set the increment. Operation may then return to and continue from block 991. If the user did not wish to increase the noise threshold at step 992, operation may proceed to step 993 where the user is asked if they would like to exit armature mode and enter normal mode, on the assumption that too much noise is present in the operating environment. local active noise. If the user selects a normal mode transition, that normal mode transition, which may use, for example, the method 900 shown in FIG. 12a is performed at step 994. On the other hand, if the user does not choose to go to normal mode at step 993, operation proceeds to step 995, which is optional, but selects the depth signal frequency based on satisfaction of another set of noise specifications. Operation then proceeds to step 987. One variation of step 995 can be seen in step 12e, as will be described immediately below, although the procedure shown in FIG. 12e can be navigated independently of the method 982 shown in FIG. 12d.

Let us now turn to FIG. 12e, which illustrates another variation of the method presented at step 950 shown in FIG. 12b, this option is generally indicated by pos. 1000, or this option may serve as step 995 shown in FIG. 12d, for the purpose of analyzing scanned frequencies in the frequency band(s) of the depth signal. It should be noted that the method 1000 may serve as a primary option for identifying the frequency of the depth signal and/or as an additional check procedure (step 995 in FIG. 12d) to ensure that the identified frequency is low enough to be practically usable, as will become apparent from the following description. In this regard, it should be noted that immunity to passive interference generally increases as frequency decreases, so it may be advantageous to use the lowest frequency that is practical to use. The method starts at step 1004 and proceeds to step 1006, where the lowest noise frequency, f(low), in the armature band is found based on the noise scan, for example, in 5 Hz steps. At 1008, although it is not a requirement, the amount of offset from the lower limit of the rebar range may be determined. At step 1010, this shift amount can be compared with a threshold shift amount, which should indicate that the frequency f(low) is already close enough to the lower limit of the armature range. If it is determined that the offset amount found is acceptable, the identified low noise frequency may be indicated and/or automatically selected at 1014. At 1016, the procedure may return to, for example, a general frequency selection procedure that also selects symbol frequencies as this is done, for example, at step 950 shown in FIG. 12b. On the other hand, if it is determined in step 1010 that the shift amount is too large, operation may proceed to step 1020 where the index value n is set, frequency steps are counted to scan armament range noise starting from the lower limit (n ^::: 1) reinforcing range and ending with the number n(low) of steps, which is the value of n corresponding to the frequency f(low). At block 1024, if the amount of noise for the frequency identified by the current value n is within the specified limits, operation may proceed to block 1014. It should be noted that acceptable limits may be determined in any suitable manner, such as, for example, no more than some predetermined value above the measured noise level at the frequency f(low). If the noise level does not fit within the established limits, the work is directed to step 1026, where the value of n is increased. At step 1028, it is then checked whether the current value n is equal to the value n(low). If so, at 1030, the frequency f(low) may be displayed and/or automatically selected as the depth signal frequency. Thereafter, operation may return to block 950 shown in FIG. 12b. If the value of n at step 1028 is less than the value of n(low), operation returns to step 1024 to compare the noise level at the specified frequency with acceptable limits, as discussed above. With this approach, a loop is formed that checks at each step the increased frequency of the depth signal, up to the frequency f(low), so that an acceptable frequency can be found that is below the actual frequency, where the lowest noise level is noted, in the armature range.

In FIG. 13 is a logic diagram illustrating one of the ways in which the locator 20 operates during underground operations, generally denoted pos. 1100. The implementation of the method begins at step 1104 and continues simultaneously along the depth determination branch 1110 and the data extraction branch 1112. The depth leg 1110 receives the depth signal 120 at 1120 and then determines the depth at which the transmitter is located at 1124. Because the depth signal is transmitted on a dedicated frequency, the signal is received on an essentially continuous basis during all underground operations. Accordingly, steps 1120 and 1124 are repeated as a loop while the locator is operating in normal operating mode. As described above, step 1124 may use the depth signal to determine the depth of the transmitter based on the dipole equations. In one embodiment, part of the depth determination procedure may include compensating for the influence of distance from the locator to the ground. In one embodiment, for receiving multiple depth signal frequencies, such as, for example, frequencies from the RBL, RBM and RBH bands (see Fig. 6c), it should be noted that the average level of these signals can be used for depth purposes. The data extraction branch 1112 begins at step 1130 with the reception of the data signal 122 in the form of a symbol stream, which may be constructed from multi-bit symbols. At 1134, this symbol stream may be temporarily stored for decoding, for example, in memory 714 (FIG. 9a). At 1138, processor 710 decodes the symbol stream. In this case, one of the symbols may be used as a sync symbol, which may identify the start of a burst structure. In one embodiment, using a 4-bit symbol (ie, 16 symbol rates), seventeen symbol rates may be added for purposes of representing the sync symbol in the symbol stream. One suitable packet structure, as a non-exhaustive example, can be represented by a set of 4-bit variables such as S, PI, R1, P2, R2, BT1, BT2, R3, where S has a fixed value corresponding to the sync symbol. The symbol PI denotes a variable representing the first four bits (0-3) of the pitch value, the symbol R1 denotes the first roll variable characterizing the roll orientation. Symbol P2 denotes bits 4-7 of the pitch value, symbol BT1 denotes the first four bits (0-3) of the accumulator and temperature data. The symbol BT2 denotes bits 4-7 of the accumulator and temperature data, and the symbol R3 denotes the third roll variable. In this regard, it should be understood that the pitch value is accumulated based on two different variables corresponding to two symbols in the symbol stream that are separated by another symbol. In other words, four bits of the P2 symbol may be added to the four bits of the PI symbol to represent the total pitch value. More bits may be added based on another pitch variable, if desired. Similarly, 8 bits of battery and temperature data can be collected based on two serial variables BT1 and BT2. At 1140, the data stream may be reassembled from the decoded symbol stream to reconstruct the original data that provided the basis for the symbol stream at transmitter 130. At 1144, processor 710 extracts parameters from the data stream. These parameters may be attitude parameters such as pitch and roll, temperature, pressure, battery voltage and current, and any other data of interest. At 1148, processor 710 responds to the extracted parameters in some suitable manner, such as, for example, operating display 36 to display on-screen pitch and roll values, battery status, temperature and pressure, and/or input to other processes, such as , for example, issuing warnings or alarms when temperature and pressure thresholds have been violated. Operation then returns to block 1130.

At this point, it is appropriate to consider other details regarding the operation of transmitter 130 during underground operations. Transmitter options can flexibly allocate transmit power between different transmitted frequencies, such as between the frequencies shown in Tables 3 and 4. In one embodiment, each frequency can be allocated the same amount of transmit power on par with other frequencies. Alternatively, the transmit power may be unevenly distributed among the frequencies. For example, one or more frequencies may be allocated more transmit power than another group of frequencies. In yet another embodiment, each frequency can be assigned its own, different from other frequencies, the transmission power. Such power allocation may be implemented in any suitable manner. For example, the portable device 20 shown in FIG. 1 and 9 may be configured to monitor the average signal strength associated with each frequency, where each frequency signal is received during normal operation. The transmit power can then be redistributed directly during operation between frequencies based on the moving average of the signal level. For example, a sharp drop in signal strength at a particular frequency can be attributed to interference so that additional power can be allocated to that frequency. In some embodiments, frequencies with low noise levels may be assigned relatively low transmit powers. The reallocated transmit power values may be transmitted to transmitter 130 in any suitable manner. For example, portable device 20 may transmit the power distribution scheme to drilling rig 80 via telemetry signal 44. The drilling rig may then transmit the new power distribution to transmitter 130 via the drill string using the latter as the electrical conductor. Alternatively, portable device 20 may be configured with an additional antenna 712 (FIG. 1), such as a dipole antenna, to transmit a signal for direct reception by transmitter 130. The modulation of this signal may be decoded by transmitter 130 to extract a new power scheme.

Referring again to FIG. 10b, distribution of power between selected frequencies may also be performed during a frequency selection procedure or mode before transitioning to the normal mode or armature mode. For example, the power allocation may be based on the noise level associated with each selected frequency, as shown in FIG. 10a and 10b. Although for the low noise frequencies identified in FIG. 10a and l0d show approximately the same noise levels for illustration purposes, this situation is not necessarily the case in reality. If there are significant variations between the noise levels at the identified frequencies with the lowest noise levels, it is possible to allocate an increased proportion of the transmit power to those frequencies at which relatively higher noise levels are recorded. In contrast, the transmit power allocated to a very low noise frequency may be relatively low so that additional power can be allocated to one or more other frequencies. The transmit power may also be distributed such that such distribution is matched using a forbidden window as described above. For example, if a particular frequency is chosen such that any power frequency harmonic or other noise falls abnormally into the bandgap for that particular frequency, additional power may be allocated to that particular frequency. It should be understood that in any embodiment using transmit power allocation, which may vary from frequency to frequency, such allocation can be made based on total power consumption, especially if transmitter 130 is powered by batteries. With this approach, the total power consumption can be reduced or the target value of the total power consumption can be maintained.

Applicants recognize that armature mode depth signal transmission, as described herein, at lower frequencies compared to data symbol frequencies, which are much higher, is a concern. In this regard, as the frequency of the depth signal decreases relative to a particular frequency of the data signal, even without any change in active interference and in the absence of any countermeasures, the range at which the depth signal can be received decreases, according to the observations of the Applicants. , compared to the range at which the data signal can be received. This can be quite problematic during operation, since the locator 20 may lose reception of the depth signal 120 much earlier than the loss of reception of the data signal 122. To ensure that the full capabilities of the system are realized, it is necessary that the locator receive both signals - both the depth signal and the data signal. Without wishing to be bound by any theory, Applicants believe that the reduction or reduction in low frequency reception range is due to a reduction in communication efficiency between the transmitting and receiving antennas. At the same time, the antenna behaves primarily like an inductor, so the antenna impedance decreases as the frequency decreases. With a fixed excitation voltage, the current increases at least in a substantially linear fashion. According to the observations of the Applicants, the reduction in the signal level and thus the range of reception of the depth signal is complex in nature. In various embodiments, suitable transmit powers to compensate for such a reduction may be determined in any suitable manner, such as empirically. This decoupling effect can be compensated for with a multiplier table, or a function, eg based on curve fitting, can be defined for use by the transmitter processor to set the transmit power based on the frequency. In order to maintain at least approximately the same reception range for the depth signal and the data signal, it can be used, for example, to adjust the depth signal to at least 100 times the power of the data signal. This regulation can be balanced by reducing the power allocated to the data signal to accommodate the rebalancing and power shift to the depth signal without violating the maximum power threshold, or by reducing the power allocated to the depth signal while allocating additional power to the signal. data for the same reason. As another example, for a depth signal frequency of 330 Hz and a data signal frequency of 18 kHz, about 5 times more power can be allocated to the depth signal than to the data signal. In light of these considerations, Applicants have proposed an improved system in which the transmitter processor is configured to generate a depth driver input at the frequency of the depth signal and to generate a data driver input indicative of the sensor data to control the depth signal transmit power relative to the data signal transmit power, thus so that the first depth signal receiving range is at least approximately the same as the second data signal receiving range, even though the frequency of the depth signal is much lower (eg, 1 kHz or less) than the frequency of the data signal. In other words, compensation is accomplished by balancing the transmit power between the depth signal and the data signal so that the reception ranges of both of these signals are at least approximately the same. At the same time, such balancing may take into account the additional requirement to manage the total power consumption of the transmitter in such a way that, for example, a given maximum power consumption is not exceeded. In one embodiment, the multiplier table 410 in Table 3 may be configured, at least approximately, based on the above range reduction characteristic, although this is not a requirement. In Table 3, it should be obvious that the transmit power depends on the value of the multiplier.

The above description of the present invention has been presented for the purpose of illustration and description. It is not intended to be exhaustive or in any way limit the present invention to exactly the form or forms that have been described, so other modifications and changes are possible in light of the above provisions. Accordingly, those skilled in the art will be able to determine a number of modifications, permutations, additions, and partial combinations of the options described above.

All elements, parts and steps described herein are preferably included. It should be clear that any of these elements, parts and steps can be replaced by other elements, parts and steps or eliminated, as will be obvious to specialists in this field.

Broadly, the proposed text describes at least the following: a transmitter for use in a submerged state controls the transmit power of the depth signal relative to the transmit power of the data signal so that the first depth signal reception range is at least approximately matched with a second, different from the first range of data signal reception. The portable device may form a transmitter system in which the portable device scans multiple frequencies within at least one low frequency depth signal range to measure electromagnetic noise levels at each of the multiple frequencies and identify at least one of the frequencies as a potential depth signal frequency. for the transmitter. This portable device may contain a dual mode filter comprising a rebar mode filter and a normal mode filter. The depth signal frequency can be dynamically positioned relative to low frequency noise.

Concepts

The present description proposes at least the following concepts.

1. A transmitter for use in conjunction with a horizontal directional drilling system comprising a drill string extending from the drill rig to a buried tool that supports the transmitter such that extending and retracting the drill string moves the buried tool underground during underground works, containing:

antenna;

one or more than one sensors for generating sensor data;

an antenna driver for electrically driving the antenna so as to radiate a depth signal in response to an input depth driver signal for overhead reception for use in determining the depth of said submerged instrument, as well as electrically driving the antenna in response to an input data driver signal, in order to to emit at least one data signal indicative of sensor data using at least one data signal frequency that is higher in frequency than the depth signal to extract said sensor data above ground, and

a processor configured to generate said depth driver input at said depth signal frequency and to generate said data driver input indicative of said sensor data so as to control depth signal transmission power relative to data signal transmission power such that one receiving range said depth signal is at least approximately matched to another, different range of receiving said data signal.

2. The transmitter of Concept 1 wherein the processor is further configured to adjust said data signal receiving range in combination with said depth signal receiving range control.

3. A transmitter of concept 1 or 2, wherein the processor is configured to adjust said data receive range in combination with said depth receive range such that the total power consumed by the transmitter does not exceed a predetermined limit.

4. The transmitter of concepts 1-3, in which the frequency of the depth signal is selected within the frequency range of the depth signal.

5. The transmitter of Concept 4 wherein the processor is configured to adjust said depth driver input so that the depth signal reception range is at least approximately equal to the data signal reception range for any selected depth signal frequency within a specified depth signal frequency range. .

6. The transmitter of concepts 4 or 5, wherein said depth driver input is a sinusoidal signal having an amplitude, and said processor is configured to adjust said depth signal reception range by varying said amplitude based, at least in part, on a specific position the specified depth signal in the specified frequency range of the depth signal.

7. The transmitter of concepts 1-6 wherein the processor is configured to generate said depth driver input and data driver input such that more power is allocated to the depth signal than to the depth signal to increase the range of the data signal when, in Otherwise, the range of the data signal would be less than the range of the data signal if each of the signals, the depth signal and the data signal, are transmitted with the same power.

8. Transmitter of concepts 1-7, in which the depth signal is less than 1 kHz.

9. Transmitter according to concepts 1-7, in which the depth signal is in the range from 300 Hz to 1 kHz, inclusive.

10. A transmitter for use in conjunction with a horizontal directional drilling system comprising a drill string extending from the drill rig to a buried tool that supports the transmitter such that extending and retracting the drill string moves the buried tool underground during underground works, containing:

antenna:

one or more than one sensors for generating sensor data;

an antenna driver for electrically driving the antenna so as to emit a depth signal in response to a depth driver signal for surface reception for determining the depth of a buried tool, and for electrically driving the antenna so as to emit a data signal indicative of sensor data using at least one data signal frequency that is higher in frequency than said depth signal to extract said sensor data above ground; And

a processor configured to generate said depth driver signal at a depth signal frequency and capable of generating said data driver signal at said data signal frequency so as to control a first receiving range of said depth signal relative to a second receiving range of said data signal.

11. System containing:

a transmitter configured to move underground in an area during a work procedure while transmitting a depth signal at a depth signal frequency that is selected in the depth signal frequency range below 1 kHz to provide at least some immunity to passive interference, and which also subject to electromagnetic noise, which may vary within the specified area; And

a portable device capable of scanning a plurality of frequencies in a specified frequency range of a depth signal to measure electromagnetic noise at each frequency of said plurality of frequencies and to identify, based on the measured noise, the lowest frequency of said frequencies as a potential depth frequency that satisfies the low noise requirement .

12. The system of concept 11 wherein, in evaluating the low noise requirement, the measured noise for each frequency of a specified set of frequencies is compared with a threshold value as part of a procedure for identifying a specified potential depth frequency.

13. The system of concept 11, in which the requirement for low noise is based on a relative comparison of the measured electromagnetic noise at each frequency from a specified set of frequencies.

14. The system of concepts 11-13 wherein the portable device is configured to advise the user of a specified potential depth frequency.

15. The system of concepts 11-14 wherein the portable device is configured to automatically select a potential depth frequency as the indicated depth frequency.

16. The system of concept 15, wherein the portable device is configured for the user not to accept a specified potential depth frequency as the depth frequency.

17. The system of concept 11 wherein the portable device is configured to at least ask the user for confirmation of a preferred depth frequency.

18. The system of concepts 11-17 wherein said portable device is configured to identify at least one potential standby depth frequency from said plurality of frequencies that is higher than said potential depth frequency, being the next lowest frequency in said frequency range, among the specified set of frequencies that satisfy the specified noise requirement.

19. The system of concept 18, in which the portable device is configured to enter a real-time noise scan mode to scan electromagnetic noise along an intended path at least at a preferred depth frequency and at a specified backup depth frequency and indicate to the operator the real-time noise level for the specified preferred depth frequency and the specified backup depth frequency.

20. The system of concepts 11-19, wherein the portable device is further configured to scan another plurality of frequencies above 1 kHz to select at least one frequency of the data signal based on electromagnetic noise measurements at each frequency of said plurality of frequencies above 1 kHz, and the transmitter further comprises one or more than one sensors that generates sensor data and is configured to transmit said sensor data using at least said data signal frequency.

21. A portable device as part of a system in which the transmitter is configured to travel underground in an area during a work procedure while transmitting a depth signal containing

an antenna having an output; And

a receiver configured to scan a plurality of frequencies in a depth signal frequency range below 1 kHz to measure electromagnetic noise at each frequency of said plurality of frequencies based on the antenna output, and to identify as a potential depth frequency that frequency which is the lowest frequency of the specified frequencies and satisfies the requirement of low noise.

22. A portable device as part of a system in which the transmitter is configured to travel underground in an area during a work procedure while transmitting a depth signal containing

an antenna having an output; And

a receiver configured to measure electromagnetic noise based on an antenna output signal in at least two different frequency bands below 1 kHz by step-scanning each frequency band to generate a plurality of step-wise samples of the noise level in each frequency band and presenting on a display one or more one potential depth frequencies for each frequency band, to be selected by the operator based on specified step-by-step noise readings.

23. The portable device of concept 22, wherein the receiver is further configured to select a potential depth frequency for each frequency band as corresponding to the lowest of said incremental noise levels from each frequency band, and to at least display the specified potential depth frequency for each frequency band to select one of the specified potential depth frequencies as the depth frequency for the specified depth signal.

24. The portable device of concept 23, configured to identify at least a specified depth frequency for a transmitter to transmit during a specified operating procedure.

25. The portable device of concept 23 or 24 configured to present a group of potential depth frequencies to select an additional frequency from said potential depth frequencies as a backup depth frequency for said depth signal.

26. The portable device of concept 25, configured to additionally identify a specified depth frequency and a specified backup depth frequency for a transmitter to transmit from the portable device during said operating procedure.

27. The portable device of concepts 23-26 configured to automatically select one of said potential depth frequencies as said depth frequency of said depth signal.

28. The portable device of concepts 22-26, configured to enter a real-time noise level display mode after displaying a specified group of potential depth frequencies, so as to continuously present real-time noise level readings for each potential depth frequency.

29. The handheld device of concept 28, configured for the operator to select one of the potential depth frequencies as the specified depth frequency of the specified depth signal while in a real-time noise level display.

30. The handheld device of concepts 22-29, configured to receive a depth signal from a transmitter during an operating procedure to determine transmitter depth.

31. System containing:

a transmitter that is operable to move in an area underground during an operating procedure while transmitting a depth signal at a depth frequency that is selectable in the depth signal frequency range below 1 kHz to provide at least some immunity to passive interference, and which is also exposed to electromagnetic noise, which may vary in the specified area; And

a portable device capable of measuring electromagnetic noise based on an antenna output signal in at least two different frequency bands below 1 kHz by step scanning each frequency band to generate a plurality of step readings of the noise level in each frequency band, and displaying one or more than one potential depth frequency for each frequency range, to be selected by the operator based on specified step-by-step noise readings.

32. The system of concept 31 wherein the portable device is further configured to select a specified depth potential frequency for each frequency band as corresponding to the lowest of said incremental noise level samples from each frequency band, and to at least be presented on a display the specified potential depth frequency for each frequency band to select one of the specified potential depth frequencies as the depth frequency for the specified depth signal.

33. A portable device as part of a system in which the transmitter is configured to move in an area underground during a working procedure, while transmitting a depth signal at a depth frequency and a data stream at one or more than one data frequency, which at least characterizes the parameter transmitter orientation, containing

an antenna for receiving said depth signal and said data frequencies to generate an output signal;

a switchable filter section for limiting the normal mode antenna output to one frequency band above a given frequency so as to pass said depth signal and said data stream at one or more than one frequency, and to limit said armature mode antenna output to another frequency band, so as to pass the specified depth signal at a frequency below the specified specified frequency and skip the specified data stream, including one or more than one frequency above the specified specified frequency; And

a processor configured to switch said switchable filter section between normal mode and armature mode to extract said depth signal and said data stream in response to the selection of normal mode and armature mode.

34. The portable device of concept 33 wherein the switchable filter comprises a normal mode filter for said normal mode and an armature filter for said armature mode.

35. A portable device according to concept 33 or 34, in which the specified target frequency is 1 kHz.

36. A portable device according to concept 34 or 35, in which the specified armature filter includes a low-frequency bend at a frequency below 1 kHz, and the specified normal mode filter includes a low-frequency bend at a frequency above 1 kHz.

37. The portable device of concepts 34-36 wherein said armature filter defines a armature bandwidth that is greater than the normal mode bandwidth that is defined by said normal mode filter.

38. The portable device of concept 37, wherein the first upper bend of said rebar bandwidth at least approximately coincides with the second upper bend of said normal mode bandwidth.

39. A portable device according to concept 37 or 38, in which the specified reinforcement bandwidth passes additional low-frequency noise compared to the specified normal mode bandwidth, and the specified portable device is additionally configured to scan electromagnetic noise at least below the specified specified frequency for identification by at least one low noise frequency for use by the transmitter as an armature depth frequency in said armature band to dynamically position said armature frequency relative to said additional low frequency noise.

40. The system of concept 39 wherein the portable device is configured to transmit said identified low noise frequency to a transmitter for use as said depth signal frequency.

41. A system containing:

a transmitter that is configured to move in a subterranean region during an operating procedure while transmitting a depth signal at a selectable depth signal frequency set to any of a plurality of step-spaced frequencies in the depth signal frequency range below 1 kHz to provide at least some immunity to passive interference, and which is also exposed to low-frequency electromagnetic noise with frequencies below 1 kHz, which can vary in the specified area, and is capable of transmitting a data signal, which at least characterizes the orientation of the transmitter, in the data frequency range above 1 kHz; And

portable device configured to scan said plurality of step-spaced frequencies below 1 kHz to measure electromagnetic noise at each of said plurality of step-spaced frequencies to identify at least one low noise frequency to establish said depth frequency in the transmitter to dynamically position said signal frequency depth relative to the specified low frequency noise.

42. The system of concept 39 wherein the portable device is configured to transmit said identified low noise frequency to a transmitter for use as said depth signal frequency.

43. A portable device as part of a system containing a transmitter that is configured to move in an area underground during a work procedure, containing

receiver configured to

(i) scanning a plurality of step-spaced frequencies below 1 kHz to measure electromagnetic noise at each of said plurality of step-spaced frequencies to identify at least one low noise frequency for use by said transmitter as said depth frequency to dynamically position said depth signal frequency relative to said low frequency noise and identifying at least one data signal frequency in a data frequency range above 1 kHz for transmission from said transmitter, to characterize at least one orientation parameter of said transmitter; And

(ii) detecting said depth signal during a work procedure to at least characterize the transmitter location depth, and detecting said data signal to at least extract said orientation parameter during a work procedure.

Claims (67)

1. A transmitter for use in conjunction with a horizontal directional drilling system comprising a drill string extending from the drill rig to a buried tool that supports the transmitter such that extending and retracting the drill string moves the buried tool underground during underground works, containing: antenna; one or more than one sensors for generating sensor data; an antenna driver for electrically driving the antenna so as to radiate a depth signal in response to an input depth driver signal for overhead reception for use in determining the depth of said submerged instrument, as well as electrically driving the antenna in response to an input data driver signal, in order to to emit at least one data signal indicative of sensor data using at least one data signal frequency that is higher in frequency than the depth signal to extract said sensor data above ground, and a processor configured to generate said input depth driver signal at a frequency of the depth signal, and configured to generate said input data driver signal indicative of said sensor data so as to control the transmission power of the depth signal relative to the transmission power of the data signal so that one receiving range of the specified depth signal corresponded to another different receiving range of the specified data signal. 2. The transmitter of claim 1, wherein the processor is further configured to adjust said data signal receiving range in conjunction with adjusting said depth signal receiving range. 3. The transmitter of claim 2, wherein the processor is configured to adjust said data range in combination with said depth range so that the total power consumed by the transmitter does not exceed a predetermined limit. 4. The transmitter of claim. 1, in which the frequency of the depth signal is selected within the frequency range of the depth signal. 5. The transmitter of claim 4, wherein the processor is configured to adjust said depth driver input such that the depth signal receiving range is equal to the data signal receiving range for any selected depth signal frequency within said depth signal frequency range. 6. The transmitter of claim 4, wherein said depth driver input is a sinusoidal signal having an amplitude, and said processor is configured to adjust said depth signal reception range by varying said amplitude based at least in part on a particular position of said depth signal in the specified depth signal frequency range. 7. The transmitter of claim 1, wherein the processor is configured to generate said depth driver input and data driver input such that more power is allocated to the depth signal than to the depth signal to increase the range of the data signal when, otherwise, In this case, the range of the data signal would be less than the range of the data signal if each of the signals - the depth signal and the data signal - are transmitted with the same power. 8. The transmitter of claim. 1, in which the depth signal is less than 1 kHz. 9. The transmitter of claim. 1, in which the depth signal is in the range from 300 Hz to 1 kHz, inclusive. 10. A transmitter for use in conjunction with a horizontal directional drilling system comprising a drill string extending from the drill rig to a buried tool that supports the transmitter such that extending and retracting the drill string moves the buried tool underground during underground works, containing: antenna: one or more than one sensors for generating sensor data; an antenna driver for electrically driving the antenna so as to emit a depth signal in response to a depth driver signal for surface reception for determining the depth of a buried tool, and for electrically driving the antenna so as to emit a data signal indicative of sensor data using at least one data signal frequency that is higher in frequency than said depth signal to extract said sensor data above ground; And a processor configured to generate said depth driver signal at a depth signal frequency, and configured to generate said data driver signal at said data signal frequency so as to control a first receiving range of said depth signal relative to a second receiving range of said data signal. 11. Horizontal directional drilling system, comprising: a transmitter capable of moving underground in an area during a work procedure, while transmitting a depth signal at a depth frequency in the depth signal frequency range below 1 kHz, to provide at least some resistance to passive interference, and which is also subject to electromagnetic noise , which can vary within the specified area; And a portable device configured to scan a plurality of frequencies in a specified depth signal frequency range to measure electromagnetic noise at each frequency of said plurality of frequencies and to identify, based on the measured noise, the lowest frequency of said frequencies as a potential depth frequency that satisfies the low noise requirement . 12. The system of claim 11 wherein, in evaluating the low noise requirement, the measured noise for each frequency of said plurality of frequencies is compared with a threshold as part of a procedure for identifying said potential depth frequency. 13. The system of claim 11, wherein the requirement for low noise is based on a relative comparison of the measured electromagnetic noise at each frequency of said plurality of frequencies. 14. The system of claim 11 wherein the portable device is configured to advise the user of a specified potential depth frequency. 15. The system of claim 11, wherein the portable device is configured to automatically select a potential depth frequency as the indicated depth frequency. 16. The system of claim 15, wherein the portable device is configured for the user not to receive said potential depth frequency as the depth frequency. 17. The system of claim 11, wherein the portable device is configured to at least ask the user for confirmation of a preferred depth frequency. 18. The system of claim. 11, in which the specified portable device is configured to identify at least one potential backup depth frequency from the specified set of frequencies, which is higher than the specified potential depth frequency, and is the next lowest frequency in the specified frequency range, among the specified sets of frequencies that satisfy the specified noise requirement. 19. The system of claim. 18, wherein the portable device is configured to enter a real-time noise scan mode to scan electromagnetic noise along the intended path at least at a preferred depth frequency and at a specified backup depth frequency and indicate to the operator the real-time noise level. time for the specified preferred depth frequency and the specified backup depth frequency. 20. The system of claim 11, wherein the portable device is further configured to scan another plurality of frequencies above 1 kHz to select at least one frequency of the data signal based on electromagnetic noise measurements at each frequency of said plurality of frequencies above 1 kHz, and the transmitter further comprises one or more than one sensors that generates sensor data, and is configured to transmit said sensor data using at least the specified data signal frequency. 21. A portable device as part of a horizontal directional drilling system in which the transmitter is configured to travel underground in an area during a work procedure while transmitting a depth signal containing an antenna having an output; And a receiver configured to scan a plurality of frequencies in a depth signal frequency range below 1 kHz to measure electromagnetic noise at each frequency of said plurality of frequencies based on the antenna output, and to identify as a potential depth frequency that frequency which is the lowest frequency of the specified frequencies and satisfies the requirement of low noise. 22. A portable device as part of a horizontal directional drilling system in which the transmitter is configured to travel underground in an area during a work procedure while transmitting a depth signal containing an antenna having an output; And a receiver configured to measure electromagnetic noise based on an antenna output signal in at least two different frequency bands below 1 kHz by step-scanning each frequency band to generate a plurality of step-wise samples of the noise level in each frequency band and presenting on a display one or more one potential depth frequencies for each frequency band, to be selected by the operator based on specified step-by-step noise readings. 23. The portable device of claim 22, wherein the receiver is further configured to select a potential depth frequency for each frequency band as corresponding to the lowest value of said incremental noise floor samples from each frequency band and to at least display the specified potential depth frequency for each frequency band to select one of the specified potential depth frequencies as the depth frequency for the specified depth signal. 24. The portable device of claim 23, configured to identify at least said depth frequency for a transmitter to transmit during said operating procedure. 25. The portable device of claim 23, configured to present a group of potential depth frequencies for selecting an additional frequency from said potential depth frequencies as a backup depth frequency for said depth signal. 26. The portable device of claim 25, configured to further identify said depth frequency and said spare depth frequency for a transmitter to transmit from the portable device during said operating procedure. 27. The portable device of claim 23, configured to automatically select one of said potential depth frequencies as said depth frequency of said depth signal. 28. The portable device of claim 22, configured to enter a real-time noise level display mode after presenting said group of potential depth frequencies on the display, so as to continuously present real-time noise level readings for each potential depth frequency on the display to the operator. depth frequencies. 29. The portable device of claim 28, configured for an operator to select one of the potential depth frequencies as said depth frequency of said depth signal while in a real-time noise level display mode. 30. The portable device of claim 22, configured to receive a depth signal from a transmitter during an operating procedure to determine the depth of the transmitter. 31. A horizontal directional drilling system, comprising: a transmitter that is configured to move in an area underground during a work procedure, while transmitting a depth signal at a depth frequency that is selectable in the depth signal frequency range below 1 kHz, to provide at least some immunity to passive interference, and which is also exposed to electromagnetic noises that may vary in the specified area; And a portable device capable of measuring electromagnetic noise based on an antenna output signal in at least two different frequency bands below 1 kHz by step scanning each frequency band to generate a plurality of step noise readings in each frequency band and displaying one or more than one potential depth frequency for each frequency band, to be selected by the operator based on specified step-by-step noise readings. 32. The system of claim 31, wherein the portable device is further configured to select said potential depth frequency for each frequency band as corresponding to the lowest of said incremental noise level samples from each frequency band, and to at least displaying said potential depth frequency for each frequency band to select one of said potential depth frequencies as the depth frequency for said depth signal. 33. A portable device as part of a horizontal directional drilling system, in which the transmitter is configured to move in an area underground during an operating procedure, while transmitting a depth signal at a depth frequency and a data stream at one or more than one data frequency, which, according to at least characterizes the orientation parameter of the transmitter, containing an antenna for receiving said depth signal and said data frequencies to generate an output signal; a switchable filter section for limiting the normal mode antenna output to one frequency band above a given frequency so as to pass said depth signal and said data stream at one or more than one frequency, and to limit said armature mode antenna output to another frequency band, so as to pass the specified depth signal at a frequency below the specified specified frequency and skip the specified data stream, including one or more than one frequency above the specified specified frequency; And a processor configured to switch said switchable filter section between normal mode and armature mode to extract said depth signal and said data stream in response to the selection of normal mode and armature mode. 34. The portable device of claim 33, wherein the switchable filter comprises a normal mode filter for said normal mode and an armature filter for said armature mode. 35. The portable device of claim 33, wherein said target frequency is 1 kHz. 36. The portable device of claim 33, wherein said armature filter includes a low frequency bend at a frequency below 1 kHz and said normal mode filter includes a low frequency bend at a frequency above 1 kHz. 37. The portable device of claim 34, wherein said armature filter defines a armature bandwidth that is greater than the normal mode bandwidth that is determined by said normal mode filter. 38. The portable device of claim 37, wherein the first upper bend of said rebar band coincides with the second upper bend of said normal mode bandwidth. 39. The portable device of claim 37, wherein said reinforcement bandwidth allows additional low frequency noise to pass over said normal mode bandwidth, said portable device is further configured to scan for electromagnetic noise at least below said target frequency for identification. at least one low noise frequency for use by the transmitter as an armature depth frequency in said armature range to dynamically position said armature frequency relative to said additional low frequency noise. 40. The portable device of claim 39, wherein the portable device is configured to transmit said identified low noise frequency to a transmitter for use as said depth signal frequency. 41. A horizontal directional drilling system, comprising: a transmitter that is operable to move in an area underground during an operating procedure while transmitting a depth signal at a depth frequency set to any of a plurality of step-spaced frequencies in the depth frequency range below 1 kHz to provide at least some resistance to passive interference, and which is also affected by electromagnetic noise with frequencies below 1 kHz, which can vary in the specified area, and is capable of transmitting a data signal, which at least characterizes the orientation of the transmitter, in the data frequency range above 1 kHz; And portable device configured to scan said plurality of step-spaced frequencies below 1 kHz to measure electromagnetic noise at each of said plurality of step-spaced frequencies to identify at least one low noise frequency to establish said depth frequency in the transmitter to dynamically position said depth frequency relative to the specified electromagnetic noise. 42. The system of claim 41, wherein the portable device is configured to transmit said identified low noise frequency to the transmitter for use as said depth frequency. 43. A portable device as part of a horizontal directional drilling system containing a transmitter that is configured to move in an area underground during a working procedure, containing receiver configured to (i) scanning a plurality of step-spaced frequencies below 1 kHz to measure electromagnetic noise at each of said plurality of step-spaced frequencies to identify at least one low noise frequency for use by said transmitter as said depth frequency to dynamically position said depth frequency relative to said electromagnetic noise and to identify at least one data frequency in the data frequency range above 1 kHz for transmission from said transmitter to characterize at least one orientation parameter of said transmitter; And (ii) detecting said depth signal during a work procedure to at least characterize the transmitter location depth, and detecting said data signal to at least extract said orientation parameter during a work procedure.

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