JPH11190779A - Radar-type underground-prospecting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radar-type underground-prospecting device with superior operability. SOLUTION: A device is provided with a transmission/reception unit 10 for radiating a pulsive wave under the ground at a predetermined repetition cycle and at the same time for receiving a reflected wave returning from the ground, an amplification part 20 for amplifying the received reflected wave with an amplification rate being changed corresponding to the repetition cycle, a sampling part 30 for sampling the amplified reflected wave by a time gate being displaced for each repetition cycle, and a restoration processing part 40 for processing a sampling signal being sampled at each repetition cycle and for restoring and forming a low-frequency expansion reflected wave. Also, the device has a signal-processing part for processing an underground information signal consisting of the expansion reflected wave and for obtaining a section image information signal under the ground, and a display for displaying the image of the section image information signal being obtained by the signal-processing part. Then, the device is constituted of a first device part 1a where the transmission/reception unit 10, the amplification part 20, a sampling part 30, and the restoration processing part 40 are provided in a traveling body that can be moved, and a second device part with the signal-processing part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technology for exploring the surface of underground objects, underground caves, archeological sites, and the like.

[0002]

2. Description of the Related Art Such underground exploration techniques are disclosed in Japanese Utility Model Publication No. 63-109681, "Independent Type Exploration Apparatus" (referred to as Reference 1), and in Japanese Utility Model Publication No. 3-16083. An antenna-operated underground buried object detection device "(referred to as Document 2). The technology disclosed in Document 1 includes an antenna, a signal processing unit for imaging information obtained from the antenna, and a display device for displaying processed image information, which are integrally provided on a moving body. The work can be performed on site while viewing the image displayed on the display device. The technique disclosed in Document 2 separates an antenna unit and a signal processing unit, and exchanges information between them via a cable.

[0003]

With respect to underground exploration, there is a desire to obtain information near the ground surface and a desire to obtain information at a relatively deep depth. In such a case, in a conventional configuration equipped with a single-sized antenna, it is possible to meet either request but not both. In order to solve such a problem, the technique disclosed in the above-mentioned document 1 requires a large antenna when trying to search for a deep depth portion, and the whole device becomes 100 kg or more with such a large antenna. , And it is difficult to handle on site. Further, if it is attempted to have a search device having an antenna having a different size depending on the search conditions, the cost will be high, the space for storage and carrying will be large, and the practicality will be poor. On the other hand, in the configuration of Literature 2, since the antenna unit and the signal processing unit are connected by an electric cable, the cable hinders the exploration work on site, and the operability becomes very poor. In addition, since the cable acts on the antenna to pick up external noise, the S / N deteriorates.

[0004] As a technique for searching for an object to be detected at a relatively deep depth with high resolution, Japanese Patent Publication No. 4-71190 is disclosed.
There is something like that shown in This technology includes a transmitting / receiving unit that emits a pulse wave into the ground at a predetermined repetition cycle and receives a reflected wave returned from the ground, and changes the received reflected wave in accordance with the repetition cycle. An amplification unit for amplifying the reflected wave, a sampling unit for sampling the amplified reflected wave with a time gate displaced for each of the repetition cycles, and a low-frequency processing unit for processing a sampling signal sampled for the repetition cycle. A restoration processing section for restoring the enlarged reflected wave is subjected to image processing on a signal composed of the restored enlarged reflected wave to obtain an underground sectional image. However, in this case as well, a single antenna is provided as an antenna, and there is room for improvement in the correspondence between the vicinity of the ground surface and the deep part.

[0005] An object of the present invention is to perform an exploration with good resolution over the vicinity of the ground surface and a deep part, and furthermore, the operability thereof is good even though there are reflected waves near the ground surface. An object of the present invention is to provide a radar underground exploration apparatus capable of accurately amplifying and processing a reflected wave from a remote area.

[0006]

A feature of the first aspect of the present invention, which can achieve the above object, is to emit a pulse wave into the ground at a predetermined repetition period and return from the ground. An amplifying unit comprising a transmission / reception unit for receiving a reflected wave, and amplifying the received reflected wave at an amplification factor changed according to the repetition period, and a time during which the amplified reflected wave is displaced for each of the repetition periods. A sampling unit for sampling by a gate; and a restoration processing unit for restoring and forming a low-frequency enlarged reflected wave by processing the sampling signal sampled for each repetition period, and processing an underground information signal composed of the enlarged reflected wave. Radar-type ground, comprising: a signal processing unit that obtains a cross-sectional image information signal in the ground by using the display unit for displaying an image of the cross-sectional image information signal obtained by the signal processing unit. A survey system, the transceiver unit, in that it comprises freely replace several different antennas sizes. In the radar-type underground exploration device of this configuration, a small antenna is used when searching near the ground surface, and a large antenna is used when searching deep depths. Here, large and small mean that the effective element length of the antenna is different,
The size and the sensitivity characteristics for embedded objects are different. Further, even when the resolution to be obtained changes according to the search condition, the antenna is changed to adjust the resolution. That is, the antenna is used while replacing each antenna. Therefore, it is not necessary to prepare, for example, two types of the entire device including the antenna and other device units, and it is possible to appropriately cope with the vicinity of the ground surface and a deep depth portion only by providing a plurality of types of antennas. In the configuration of the present application, signal amplification is performed, and further, an enlarged reflected wave is formed through a sampling process to obtain cross-sectional image information, so that the structure itself can support a relatively wide depth range. At the same time, the exploration operation involving the exchange of antennas allows exploration over a wider range with low noise and high resolution.

Next, the second characteristic configuration of the present application is that a pulse wave is radiated into the ground at a predetermined repetition period,
An amplifying unit that includes a transmission / reception unit that receives a reflected wave returned from the underground, and amplifies the received reflected wave with an amplification factor changed in accordance with the repetition period; A sampling unit for sampling with a time gate displaced every time, and a restoration processing unit for restoring and forming a low-frequency enlarged reflected wave by processing a sampling signal sampled for each repetition period, and comprising the enlarged reflected wave. A radar type underground exploration device comprising: a signal processing unit that processes an underground information signal to obtain an underground sectional image information signal; and a display device that displays an image of the sectional image information signal obtained by the signal processing unit. And a first device unit including the transmitting / receiving unit, the amplifying unit, the sampling unit, and the restoration processing unit on a movable vehicle, and a first unit including the signal processing unit. And a device section separately, the display device provided in the first device portion, the second and the first device portion
Another object of the present invention is to provide a configuration including a wireless communication processing unit that performs mutual signal exchange between device units. In this configuration, the radar type underground exploration device is divided into two parts, a first device part and a second device part.
The operation can be performed by operating the device unit on site. Further, since the exchange of information between the first device unit and the second device unit is performed wirelessly, external noise is not picked up by the antenna due to the influence of the cable. The first device unit equipped with the antenna includes a transmitting / receiving unit, an amplifying unit,
Since the system includes the sampling unit and the restoration processing unit, the signal processing in the high-frequency region can be completed in the first device unit, and unnecessary noise is transferred through the exchange between the first device unit and the second device unit. In this device, it is possible to perform a search with a relatively high search capability and a high resolution, which can provide excellent mobility and operability.

[0008] Even when the configuration described in claim 2 is employed, it is preferable that the transmitting / receiving unit is provided with a plurality of antennas having different sizes in the first device section so as to be freely replaceable. In this case, in the same manner as described above, the exploration is performed on the first device unit while replacing antennas of different sizes, so that it is possible to cope well from a shallow depth to a deep depth.

[0009]

FIG. 1 is a schematic diagram showing the configuration of a radar type underground exploration apparatus according to an embodiment of the present invention. FIG. 2 is a diagram showing a first apparatus section 1a of the present invention. It is a functional block diagram. Radar type underground exploration device 1 of the present application
The first device section 1a having an antenna 13a as its main part, the second device section 1b separate from the first device section 1a, and the first device section 1b and the second device section 1b, respectively. And a display device 1c to be provided. Here, information signals are exchanged between the first device unit 1a and the second device unit 1b, and further, the second device unit 1b and the display device 1c (for the display device 62 in the second device unit 1b, Excluding), the information signal is exchanged wirelessly.

As shown in FIGS. 1 and 2, a first device section 1a
Is equipped with a transmitting and receiving unit 10 for transmitting electromagnetic waves underground and receiving a reflected wave reflected back from the object 3 underground, samples information obtained by this unit 10, and further performs sampling processing. This is a part for obtaining a low-frequency enlarged reflected wave from the sampling signal. The second device 1b performs signal processing for converting an underground information signal including a plurality of enlarged reflected waves obtained at a plurality of search positions into a cross-sectional image information signal. Therefore, by providing this cross-sectional image signal to the display device 1c, the display device 1c can display a cross-sectional image.

Hereinafter, each device will be sequentially described. As shown in FIG. 2, the main components of the first device section 1a radiate pulsed radio waves in the microwave region toward the ground surface 2 at a predetermined repetition frequency, and bury objects such as buried objects existing in the ground. A transmitting / receiving unit 10 for receiving the reflected wave reflected back by the reflecting object 3, an amplifying unit 20 for amplifying the received reflected wave, and sampling for sampling the sequentially received and amplified reflected wave while shifting the sampling point. Unit 30 and a restoration processing unit 40 for combining the sampled signals to restore the reflected wave and for transmitting the restored reflected wave to the second device unit 1b
And a blocking unit 50 for controlling a signal flow between the transmitting / receiving unit 10 and the amplifying unit 20. This first device section 1a
Is configured to be provided on the traveling body 100, and is configured to be free-standing or capable of traveling by an operator. Further, the traveling body 100 is provided with a detector (not shown) for detecting the traveling distance, and the position X of the first device unit 1a from the search reference position O is determined by the output of the detector. It is configured to be. With such a configuration, the position detection unit 45 that detects the position X of the first device unit 1a
Is configured.

The transmission / reception unit 10 includes a transmission trigger generator 11 for generating a transmission trigger pulse in accordance with a set repetition frequency, and a transmitter 1 for emitting a pulsed radio wave from the antenna 13a in response to the transmission trigger pulse.
2, and a receiving unit 14 that receives the reflected wave reflected by the underground reflecting object 3 and returned by the antenna 13a and sends the reflected wave into the apparatus. As this antenna, a plurality of antennas having different sizes are prepared, and the antennas are used while being exchanged with the transmission / reception unit 10 according to the search depth and the required resolution. The size of the antenna 13a is, for example, 30 to 60 cm for deep depth and several c for shallow depth.
m to 20 cm. In this configuration, the antenna 1
Since only a single unit 3a is provided, a diplexer 13b is provided between the antenna 13a, the transmitting unit 12, and the receiving unit 14.

The amplifying section 20 has an STC (Sensitivity Time C).
ontol: Sensitivity time control) A signal generation unit 21 and an amplifier 22 are provided, and the STC signal generation unit 21 generates an STC signal that increases in each cycle of a transmission trigger pulse.
The amplifier 22 increases the amplification factor by the C signal. For example, a full-range 100 dB amplification factor of 1000
It is increased step by step in each cycle of the transmission trigger pulse. In this case, when receiving 1000 transmission trigger pulses, the amplification factor is returned to the lowest level again, and a similar increase in the amplification factor is started. In such automatic gain control of the amplifier 22, the ST changes in every cycle of the transmission trigger pulse.
This is done by the C signal. Therefore, this STC
By adjusting the signal, any time-varying amplification factor can be created.

The sampling unit 30 includes a sampler driving unit 31 that determines a sampling timing in response to a transmission trigger pulse, and a sampler 32 that samples a reflected wave amplified by a command from the sampler driving unit 31 at a predetermined time point. It has. The sampling unit 30 samples each reflected wave sent from the amplifying unit 20 in the repetition cycle using a sampling gate whose sampling point is sequentially shifted on the time axis. That is, sampling is performed at one sampling point from the reflected wave received by the first transmitted wave, and is sampled at a sampling point slightly delayed from the reflected wave received by the next transmitted wave. By performing this operation twice, sampling of the entire reflected wave in a desired time region is completed. That is, a sampling signal of one entire reflected wave is obtained from the 1000 reflected waves sequentially received. Restoration processing unit 40
Is configured to include a signal restoration processing unit 41 for restoring a reflected wave from the signal sampled by the sampling unit 30. The signal restored in the low frequency state is transmitted to the first communication unit 42 via the first communication unit 42. The configuration is such that the data is sent to the second communication unit 43 provided in the two device unit 1b. Separately, the position information X obtained by the position detection unit 45 described above is also used together with the above-mentioned restoration signal, with the position and the elapsed time from the generation point of the restoration reflection signal (actually, the reflection of the signal wave from the underground object). Time).

The cut-off means 50 includes the receiving unit 14 and the amplifier 22
A high-frequency switch 51 interposed in the signal line between the high-frequency switch 51 and a pulse generator 52 that generates a control pulse having a desired pulse width for the high-frequency switch 51 at the same period as the transmission trigger pulse; A delay circuit 53 for delaying the control pulse on the time axis to determine the position of the time axis on which the reflected wave should be cut, and comparing the STC signal level with the reference level to determine whether the level of the STC signal is the reference level A comparator 54 that sends out a control signal when it exceeds
And an analog switch 55 that allows a control pulse from the delay circuit 53 to flow to the high-frequency switch 51 in response to a control signal from the control circuit. The cut-off means sends a control pulse to the high-frequency switch 51 when the level of the STC signal exceeds a predetermined reference level.
The reflected wave in a predetermined time region flowing to the second filter 2 is cut.

The configuration of the second device section 1b will be described. The second device section 1b includes a reflection signal converted into a low-frequency signal from the first communication section 42 and search position information X from which the reflection signal is obtained. And a signal processing unit for converting the two-dimensional information, which is the distribution of the reflection intensity on the search position-reflection time coordinate, from the second communication unit 43 into ground cross-section image information 44. This signal processing unit 4
The processing in 4 is a so-called synthetic aperture processing or a migration processing, which obtains information obtained as an intensity distribution of a reflected signal in a secondary region between the search position X and the reflection time, and outputs the information to the search position and the depth of the ground. Into related information,
This is a cross-sectional image in which an object in the ground can be confirmed. FIG. 5 shows a form of the intensity distribution of the reflection signal in the secondary region between the search position X and the reflection time. In the figure, the horizontal axis represents the spatial position X and the vertical axis represents the reflection time axis, and the state of the intensity of the reflected signal is indicated by a line along the vertical axis (this line indicates that the signal intensity is 0). From the horizontal axis of the signal line. Further, the image having undergone the synthetic aperture processing as described above is displayed on the display device 62 of FIG.
Is an image that can directly represent the underground cross-section structure as shown in FIG. The second device section 1b is provided with a second display device 62 itself, and receives and displays the cross-sectional image information signal obtained by the signal processing section 44. The exchange of information during this time is via a cable.

The radar type underground exploration device 1 of the present application is provided with two separate display devices in addition to the second display device 62 described above. In these display devices, a first display device 61 used as a portable terminal display device is provided in the first device portion 1a described above, and independently of the first device portion 1a and the second device portion 1b. The head mount display used by the field worker is provided as the third display device 63. Then, from the second communication unit 43 provided in the second device unit 1b, the respective display devices 61,
Image information can be wirelessly transmitted to 63 and displayed on a display device when necessary. The above is the schematic configuration of the present apparatus. By employing this configuration, it is possible to cope with exploration in a wide depth range by replacing the antennas 13a having different sizes. Further, the first device section 1a is independently movable so that the operability is good. Further, since the signal processing in the high-frequency region is performed in the first device section 1a, a useful enlarged restoration signal can be obtained with little noise.

The state of restoration of a reflected wave with depth correction will be described with reference to the time chart of FIG. The transmission trigger generator 11 generates a transmission trigger pulse at a period of 1 μs. Therefore, the repetition frequency of the transmission radio wave radiated from the antenna 13a is 1 Mz. The propagation speed of radio waves in the ground depends on the geology. For example, if the propagation speed is 10 cm / ns, the time required for a reflected wave from a depth of 5 m to return is 100.
ns. Usually, the exploration area such as a gas conduit is about 5m underground, so a repetition frequency of 1Mz is sufficient.

The control pulse generated by the pulse generator 52 in response to the transmission trigger pulse is sent to the analog switch 55 by the delay circuit 53 with a predetermined time delay from the rise of the transmission trigger pulse. The delay time of the control pulse is set to a time region where the reflected wave is desired to be cut, and is set to a time region where a reflected wave from the reflector 3a near the ground surface 2 normally occurs.

The STC signal is a signal that increases stepwise with the count of the transmission trigger pulse. In this embodiment, the signal returns to the lowest level after the count of the 1000 transmission trigger pulses. Since the gain of the amplifier 22 changes in accordance with the signal level of the STC signal, the amplifier 22 repeats from the lowest gain to the highest gain in a cycle of 1 ms.

In FIG. 3, with respect to the temporal change of the analog switch, the ON state is represented by a low level and the OFF state is represented by a high level, and the level of the STC signal exceeds a reference value (threshold level) which can be set in advance. , From the low level to the high level to allow the control pulse of the high frequency switch to pass from the delay circuit 53 to the high frequency switch 51. The high-frequency switch 51 is turned off (open) while receiving the control pulse, more specifically, the high-level signal, so that the reflected wave passes from the receiving unit 14 to the amplifier 22 for a time corresponding to the pulse width of the control pulse. Cut off.

The reflected wave A shown in FIG. 3 indicates the waveform of the reflected wave at the receiving unit 14, the first peak waveform indicates the reflection from the reflector 3a near the ground surface 2, and the second peak waveform
Represents the reflection from the reflector 3b away from the ground surface 2. The drawing of the reflected wave emphasizes legibility, and does not show an accurate shape with respect to its time axis or signal strength axis. This reflected wave is obtained every time the transmission trigger pulse is repeated.

The reflected wave B shown in FIG. 3 shows the waveform of the reflected wave after being amplified by the amplifier 22, and is amplified as the level of the STC signal increases. However, STC
When the signal level exceeds the reference value (threshold level), the time domain in which the first peak wave occurs is cut off by the operation of the high-frequency switch 51 by the control pulse adjusted to the first peak wave. This prevents a reflected wave having a strong signal level from near the surface at a high amplification factor from entering the amplifier 22, and prevents the amplifier 22 from saturating.

Sampling is performed by one sampling gate for one received signal of a reflected wave received at a repetition period of 1 μs. The time position of the first sampling gate is set at the position on the time axis corresponding to the ground surface 2, and thereafter sampling is performed at a point delayed by 0.1 ns every repetition cycle of the transmission radio wave. This sampling point is indicated by a vertical solid line in the sampling gate of FIG. That is, the n-th sampling is n-1
This is performed 1 μs + 0.1 ns after the second sampling.
The sampling returns to the first sampling point every 1000 times. This means that a time region of 100 ns is sampled by 1000 times of sampling, which corresponds to a region having a depth of 5 m from the ground surface 2 and is a sufficient region for exploring a gas conduit or the like. If the sampling interval is 0.1 ns, the micro can satisfactorily restore the waveform of the reflected wave in the region. In FIG.
The reflected wave restored by synthesizing signals sampled one by one from 000 reflected waves is shown. The display cycle of this reflected wave is 1 μs * 1000 = 1 ms, and the time axis is reduced by a factor of 1000. It is elongated and can be displayed on a low resolution display device. Both the reflected wave reflected from the reflector 3a near the ground surface 2 and the reflected wave reflected from the reflector 3b remote from the ground surface 2 have the same time as the STC signal despite the large attenuation rate of the radio wave in the ground. Due to the change of the dependent amplification factor, the values are displayed at almost the same level, facilitating the exploration evaluation.

By sending the signal which has been sampled and restored in this way to the image signal processing side, a highly accurate search can be performed.

The present invention is not limited to the values such as the repetition frequency and the sampling interval used in the above description, and it goes without saying that the present invention can be implemented with various values as needed.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration of a radar type underground exploration device according to the present invention.

FIG. 2 is a functional block diagram showing an example of a radar type underground exploration device according to the present invention.

FIG. 3 is a time chart showing the operation of the radar type underground survey device shown in FIG. 1;

FIG. 4 is an explanatory diagram showing a restored reflected wave.

FIG. 5 is a diagram showing a distribution state of a reflection signal in a spatial position and a reflection time domain.

[Explanation of symbols]

 1a First device unit 1b Second device unit 1c Display device 10 Transmitting and receiving unit 13a Antenna 20 Amplifying unit 30 Sampling unit 40 Restoration processing unit 100 Vehicle

Claims (3)

[Claims] A transmitting / receiving unit for emitting a pulse wave into the ground at a predetermined repetition cycle and receiving a reflected wave returned from the ground, wherein the received reflected wave is changed in accordance with the repetition cycle. An amplification unit for amplifying the amplified reflected wave, a sampling unit for sampling the amplified reflected wave with a time gate displaced for each of the repetition cycles, and a low processing unit for processing a sampling signal sampled for each of the repetition cycles. A restoration processing unit for restoring an enlarged reflected wave of a frequency, a signal processing unit for processing an underground information signal composed of the enlarged reflected wave to obtain a cross-sectional image information signal of the underground, and obtained by the signal processing unit. A radar-type underground exploration device provided with a display device for displaying an image of the cross-sectional image information signal, wherein a plurality of antennas having different sizes are replaced with the transmitting / receiving unit. Freely with radar type underground exploration device. 2. A transmission / reception unit for emitting a pulse wave into the ground at a predetermined repetition period and receiving a reflected wave returned from the ground, wherein the received reflected wave is changed according to the repetition period. An amplification unit for amplifying the amplified reflected wave, a sampling unit for sampling the amplified reflected wave with a time gate displaced for each of the repetition cycles, and a low processing unit for processing a sampling signal sampled for each of the repetition cycles. A restoration processing unit for restoring and forming an enlarged reflected wave having a frequency, a signal processing unit for processing an underground information signal composed of the enlarged reflected wave to obtain an underground cross-sectional image information signal, A radar-type underground exploration device including a display device that displays an image of the obtained cross-sectional image information signal, wherein the transmission / reception unit, the amplification unit, the sampling unit, and A first device unit provided on a traveling body capable of moving a source processing unit and a second device unit provided with the signal processing unit; the display device is provided in the first device unit; A radar-type underground exploration device including a wireless communication processing unit that exchanges signals between the first device unit and the second device unit. 3. The radar type underground exploration apparatus according to claim 2, wherein a plurality of antennas having different sizes are interchangeably provided in the transmission / reception unit.