RU2499999C2 - Method and system for determining position of signal transmitter from signal arrival time - Google Patents

Abstract

FIELD: radio engineering, communication.

SUBSTANCE: method and system for determining the position of a signal transmitter from the signal arrival time employ separate processing of a signal received by multiple antennae and receiving channels, waiting for characteristic points of the received signal, measuring the time of arrival of characteristic points of the received signal, summation with accumulation to determine the average arithmetic of measured values of the time of arrival of characteristic points of the received signal and calculating the position of the signal transmitter using the average arithmetic of the measured values of the time of arrival of the characteristic points of the received signal as the time of arrival of the signal.

EFFECT: high accuracy and longer range for determining position of a signal transmitter.

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Description

Technical field

The invention relates to the field of radio communications and, in particular, to the field of radio frequency identification. In many cases, it is necessary to determine the location of the object associated with the signal transmitter. Methods for determining location using an estimate of the distance traveled by the signal from the arrival time of the signal are well known to those skilled in the art. In these methods, the location of the signal transmitter is determined by the arrival time of the signal at several spatially separated points.

State of the art

In the subject tracking system of US Pat. No. 6,150,921 A, a method is used to determine the location of a signal transmitter by the signal arrival time by measuring the maximum response time during signal correlation processing. This method provides high accuracy and range of location, but is difficult to implement.

In a positioning system adapted for multipath propagation conditions, US Pat. No. 3,6791 E uses a “method for determining the location of a signal transmitter by the signal arrival time by measuring the time of the leading edge of the signal, which, due to the delay of the reflected rays, is caused only by a direct beam. In this method, to determine the location of the signal transmitter, it is useful to use a small part of the energy of one signal element, managing to arrive in a direct beam before The increase in accuracy of positioning in the conditions of multipath propagation of radio waves is achieved at the cost of reducing the range of positioning.

Closest to the present invention are a device, system and method for determining the location of an RF tag according to WO 2007041153 A1. The device and the system uses a method for determining the location of the signal transmitter from the time of arrival of the signal through measuring the time of a characteristic point in the interval of one signal element. By measuring the time of the same characteristic point in the interval of the subsequent signal element, the new location of the signal transmitter is determined. In this method, for each location of the signal transmitter, the energy of one signal element is useful, which does not provide the desired accuracy and range of location determination.

The system for determining the location of a radio frequency identification tag according to WO 2007041153 A1 includes several antennas, several receiving paths, each receiving path is connected to one of several antennas for processing a signal received through a corresponding antenna, a circuit for measuring the time of characteristic points of a signal connected to each of the receiving paths , as well as a scheme for calculating the location of the signal transmitter by the time of arrival of the signal.

Disclosure of invention

In the method of determining the location of the signal transmitter by the arrival time of the signal in accordance with the present invention, the location of the signal transmitter is calculated by the arrival time of the signal through 1) measuring the cyclic time of a characteristic point on the interval of the signal element for a plurality of signal elements, 2) calculating the arithmetic mean of the measurement results, and 3) using the arithmetic mean as the arrival time of the signal. In this method, a significant part of the total energy of the signal is advantageously used to determine the location of the signal transmitter, which improves accuracy and increases the range of positioning in a simpler implementation compared to a method using signal correlation processing.

The system for determining the location of the signal transmitter according to the time of arrival of the signal in accordance with the present invention contains several antennas, several receiving paths, each receiving path is connected to one of several antennas for processing a signal received through a corresponding antenna, a time measurement circuit connected to each of the receiving paths , or several time measuring circuits, each separately connected to one of several receiving paths, for measuring the time of characteristic signal points, as well as a circuit tracking the location of the signal transmitter by the time of arrival of the signal, and differs from the closest known system for determining location by the time of arrival of the signal in that it contains one summation scheme with the accumulation of measurement results for each time measurement circuit of the characteristic points of the signal, with each summation circuit with the accumulation of measurement results at the input is connected separately to one of the time measuring circuits of the characteristic points of the signal, and at the output it is connected to a location calculation circuit signal transmitter tions on the time of arrival of the signal.

Brief Description of the Drawings

Figure 1 shows an example embodiment of the invention, a system for determining the location of the signal transmitter by the time of arrival of the signal.

Figure 2 shows the structural diagram of a reader, combining one repeating part of the system for determining the location of the signal transmitter according to the time of arrival of the signal in one embodiment of the invention.

Figure 3 shows the structural diagram of the controller, combining non-repeating parts of the system for determining the location of the signal transmitter according to the time of arrival of the signal in one embodiment of the invention.

FIG. 4 is a flowchart of a process in one embodiment of a method for determining the location of a signal transmitter by signal arrival time.

The implementation of the invention

Numerous specific details are set forth in the description of embodiments of the invention. However, it should be understood that embodiments of the invention may be practiced without these specific details. In other cases, well-known schemes, structures, and technologies have not been shown in detail so as not to obscure the understanding of this description.

The phrases “embodiment”, “embodiment”, “one embodiment”, “various embodiments” and others show that the embodiment (s) of the invention described in this way may include particular features, structures or characteristics, but not every option necessarily includes particular features, structures, or characteristics. In addition, some options may have some, all, or none of the features described in other options.

In the description and claims, the terms “connected” and “connected”, as well as their derivatives, are used. It should be understood that these terms are not used as synonyms for each other. In some cases, the term “connected” is preferred to indicate that two or more elements can be in direct contact with each other. The term “connected” is used to indicate that two or more elements cooperate or interact with each other, but they may or may not be in direct contact.

For the purposes of this document, the term “signal transmitter” can refer to any digitally modulated signal source, such as a radio frequency identification tag, a radio station, a cellular communication terminal, etc., containing an electronic circuit for generating and digitally modulating a signal carrier frequency and an antenna.

Various embodiments of the invention may be implemented in one or any other combination of hardware, firmware, and software. The invention can also be implemented in the form of instructions contained in the product, or on computer storage media that can be read and executed by one or more processors to perform the operations described herein. Computer storage media may include any mechanisms for storing, transmitting and / or receiving information in a form readable by a machine (eg, a computer). Computer storage media can include such media, and not only them, such as read-only memory, random access memory, magnetic disk, optical media, flash memory. Computer storage media may also include a material medium through which electrical, optical, acoustic, and other forms of propagated signals carrying instructions can pass, for example, antennas, optical fiber, communication interfaces, and others.

In some embodiments of the invention, spatially separated parts of the system for determining the location of the signal transmitter by the time of arrival of the signal can be connected via wired interfaces to symmetrical or coaxial lines, and in other embodiments, through radio interfaces.

Some embodiments of the invention may relate to determining the location of a signal transmitter by receiving a signal through several antennas and receiving paths, measuring the time of arrival of the signal, using time differences of arrival to calculate the mutual differences in the distance between the signal transmitter and the respective antennas, and triangulating the differences in distance to calculate the location signal transmitter relative to known reference points. Other embodiments of the invention may relate to determining the location of a signal transmitter combined with a receiving path of response signals by receiving a signal through several antennas and receiving paths, transmitting response signals, and receiving the receiving path of response signals using the signal arrival time and response time for calculating the distances between the signal transmitter and the corresponding antennas and calculating the location of the signal transmitter relative to known reference points of the method th triangulation arcs.

Figure 1 shows an example location of an object location system with an attached signal transmitter, radio frequency identification tag, in accordance with an embodiment of the invention. The system includes structural units - readers 1, 2, 3, and 4, each containing one of the repeating functional parts of the system, and a controller 5 containing the non-repeating functional parts of the system. All structural units of the system are connected by segments of electric cable 6. In some embodiments, the controller 5 is connected to each reader by a separate segment of electric cable 6, in some of these variants, individual segments of electric cable 6 have the same length to introduce the same delay in the synchronization signal transmitted through them. In other embodiments, structural units are connected by pieces of electric cable 6 one after another, like bulbs in a garland. In versions with different lengths of the electric cable from the controller to different readers, different technologies can be used to compensate for different delays in the synchronization signal.

In the example of FIG. 1, four readers 1, 2, 3, and 4 are shown with integrated antennas located approximately in orthogonal directions from the area in which the RFID tags are expected to be located, although other options may use different locations for the readers and their other quantity. Figure 1 also shows the radio frequency identification tag 7 attached to the object 8. By detecting the presence and location of the radio frequency identification tag 7, the system can determine the presence and location of the object 8.

When a signal is transmitted by an RFID tag 7, the time at which the signal is received by different readers may be slightly different, due to the different propagation times of the signal to the reader antennas. Different propagation time, in turn, may be due to the difference in the distance between the tag and the corresponding antennas. The difference in reception time can therefore be used to calculate the mutual difference in the distance between the tag and each receiving antenna. Using the triangulation technique, this distance difference can be used to calculate the location of the RFID tag relative to the location of the various receiving antennas, provided that the relative distance and relative direction of each antenna from other antennas is known.

Using methods based on comparing the difference of distances (and not the distances themselves) from known landmarks, the location surface of the radio frequency identification tag 7 can be uniquely determined using two readers 1, 2, the location of the line lying on this surface using three readers 1, 2, 3 and the location of the point on this line - with the help of four readers 1, 2, 3 and 4. Thus, four readers can be used to uniquely determine the location of the mark as a point in 3-dimensional spaces With respect to the four readers (readers antennas). Although this configuration is shown in FIG. 1, other variants may use three or even two readers to uniquely determine the location of the RFID tag on the surface or line, respectively, if this is sufficient to solve an application. On the other hand, more than four readers can be used if the location needs to be determined with greater accuracy, since additional information can be used to reduce some inaccuracies caused by factors such as large antenna size, time deviation, etc.

Figure 2 shows the structural diagram of the reader, and figure 3 is a structural diagram of the controller, illustrating the distribution by structural units of the functional parts of the positioning system in an embodiment of the invention. The reader includes one repeating functional part of the system, such as: antenna 9, receiving path 10, time measuring circuit 11, and accumulation circuit 12 with accumulation 12, cascaded in the order of listing. The non-repeating functional part of the system, location calculation circuit 13, is included in the controller in this embodiment of the invention. To connect multiple accumulation schemes with accumulation 12 with the location calculation circuit 13, a data line 14 is used as part of the electric cable 6. To interface with the data line 14 of accumulation schemes 12, the transmitter includes a serial interface transmitter 15, and for pairing with the data line 14 of the location calculation circuit 13, a serial interface receiver 16 is included in the controller.

In the described embodiment, separate time measuring circuits 11 are used for each of the receiving paths 10 in each reader. To synchronize the timelines of time measuring circuits, a common synchronization source 17 is used, which in this embodiment of the invention is included in the controller. The connection of the synchronization source 17 with the time measurement circuits 11 is carried out along the synchronization line 18 as part of the electric cable 6.

To enable the location of multiple RFID tags, the tags are distinguished by their identifiers allocated by the reader from the received tag signals using a data extractor 19 connected at the input to the output of the receiving path 10 and at the output to the input of the serial interface transmitter 15. Data on the time of arrival of the tag signal and the data with the identifier of the same tag are transmitted by the transmitter of the serial interface 15 via data line 14 to the controller, where both They are extracted from the serial signal of the data line 14 by the receiver of the serial interface 16 and are fed to the location calculation circuit 13.

When the tag signal arrives through the antenna 9 and the receiving path 10 to the time measuring circuit 11, it begins to highlight characteristic points at the intervals of the signal elements, for example, the edges of the detector's bi-directional output signal. The function of the time measurement circuit can be carried out by a counter-timer and a circuit for capturing its state. Counters-timers with a capture circuit are part of the peripheral modules of many microcontrollers. The frequency of the clock signal of the counter-timer and the number of its bits are selected so that the length of the period of operation of the counter-timer coincides with the duration of the elements of the label signal. The signal of the synchronization source 17 should have the same period or a multiple of that. The phase of the counter-timer cycles and the phase of the counter-timer states are adjusted according to the signal of the synchronization source.

The captured states of the counter-timer reflect the measured time values of the characteristic points of the signal elements on a cyclic time scale with a cycle period equal to the duration of the signal element. If the location of the mark does not change during the transmission of the signal, then as a result of measurements the same cyclic time values of the characteristic points of the signal elements could be obtained. However, due to the influence of many factors, and, above all, the noise of the receiving path, the cyclic time of the characteristic point of the signal element is a random variable and its values obtained in different measurements may differ from each other.

It is known from the theory of errors that the most probable value of a random variable is the arithmetic mean of the measured values of the random variable. Moreover, the variance of the arithmetic mean is less than the variance of a random variable by a factor of N, where N is the number of random values involved in the calculation of the arithmetic mean. As applied to this application, this means that the root-mean-square error of the signal arrival time estimate can always be reduced, and therefore, the accuracy of determining the location of the signal transmitter can be improved by increasing the number of signal elements in which the characteristic point time is measured and averaging the measurement results.

The averaging operation of the measurement results is performed by the accumulation summation circuit 12. If the number of signal elements N for which the characteristic point time is measured and the measurement results are summed is 2 to the power of m, where m is an integer, then the number accumulated by the accumulation summation circuit after discarding a certain number of least significant bits can be used as an estimate of the arrival time of the signal.

The estimates of the arrival time of the signal of the same label from different readers coming to the location calculation circuit 13 are used to calculate the mutual differences of the arrival time. These differences show how closer or farther the antenna of each reader was from the signal transmitter (i.e., from the tag). Time differences are converted to distance differences by multiplying by the speed of signal propagation in the air. The position of the mark is calculated by solving a system of triangulation equations with the substitution of the known coordinates of the control points and the differences in the distances of the mark from the control points.

The following is a description of a process that implements a method for determining the location of a signal transmitter based on the arrival time of a signal, in accordance with the flowchart of FIG. 4. The process is described on the assumption that the signal comes from one transmitter, however, a similar process can follow the arrival of signals from several transmitters, using currently known, or which can be developed, methods for processing signals from several transmitters.

At step 20, the transmitter signal can be received through several antennas and corresponding receiving paths. The following steps are performed in relation to the outputs of those receiving paths on which the signal is detected. Steps 21, 22, 23 and 24 are performed with cyclic repetition a certain number of times during the time of reception of the signal.

At step 21, characteristic points are expected to appear in the received signal at the outputs of the respective receive paths. At step 22, the time is measured for the characteristic points of the signal at the outputs of the respective receiving paths. In step 23, the time values of the characteristic signal points measured at the last execution of step 23 at the outputs of the respective receiving paths are added to the previously accumulated sums of the measured time values of the characteristic signal points for all previous cycles from the beginning of signal reception to determine the arithmetic average of the measured time values of the characteristic signal points. It is assumed that before the start of signal reception, the accumulated amounts are reset to zero. At step 24, the number of summation cycles performed from the beginning of signal reception is checked and, if the number of summation cycles is equal to the predetermined number N, proceeds to step 25, otherwise, returns to step 21. It is advisable to choose the predetermined number N equal to two in degree m, where m is an integer.

At step 25, the location of the signal transmitter is calculated using estimates of the arrival time of the signal through various antennas and receiving paths, which are accumulated over N cycles of the sum of the measured time values of the characteristic points of the signal after discarding a certain number of low order bits and taking into account the discreteness of time corresponding to the lowest of the remaining digits.

The ability to accurately and far determine the location of the signal transmitter in the described manner with a simple implementation can be useful in various fields of human activity. The task of radio frequency identification with the location of tags and related items in real time is relevant for automated production, warehouses, storage. The use of similar systems to track the movement of miners, miners, rescuers, firefighters, as well as staff of the metro, long tunnels, enclosed spaces of hazardous industries, etc. will improve the safety of their work. The advantage of this technology is the ability to determine the location of any transmitter of the modulated signal, even when this feature was not laid during its development. The described method can determine the location of analog or digital radio stations, as well as subscriber terminals of cellular communication networks.

Claims (3)

1. The system for determining the location of the signal transmitter by the time of arrival of the signal, including several antennas, several receiving paths, each receiving path is connected to one of several antennas for processing the signal received through the corresponding antenna, a circuit for extracting characteristic points on the intervals of the elements of the received signal and measuring time the appearance of characteristic points of the signal connected to each of the receiving paths, or several schemes for distinguishing characteristic points at the intervals of the elements of the received signal and rhenium of the time of occurrence of characteristic signal points, each of which is connected to one of several receiving paths, as well as a scheme for calculating the location of the signal transmitter by the signal arrival time, characterized in that it includes one summation scheme with accumulation of measurement results for each characteristic point allocation circuit the intervals of the elements of the received signal and measuring the time of appearance of the characteristic points of the signal, while the input of each summation circuit with the accumulation of measurement results is connected to Odom one design, selection of feature points at intervals of elements of the received signal and measuring the time of occurrence of the signal characteristic points, and the output of each summing circuit with the accumulation of the measurement results is associated with a scheme for calculating a signal transmitter location by time of arrival signal. 2. A method for determining the location of a signal transmitter by the arrival time of a signal, including receiving a signal from a transmitter through several antennas and receiving paths, separately processing a signal received by each antenna to determine characteristic points of a received signal, measuring the time of appearance of characteristic points of a received signal, and calculating the location of the signal transmitter by the time of arrival of the signal, characterized in that it includes measuring the cyclic time of the appearance of a characteristic point on the interval cient signal for a plurality of signal elements, determining the arithmetic mean of the measured values of cyclic time of occurrence of the characteristic points of the received signal and uses the arithmetic mean of the measured values of cyclic time of occurrence of characteristic points of the received signal as a time of arrival of the signal in the calculation of the signal transmitter location by time of arrival signal. 3. The method according to claim 2, characterized in that when determining the arithmetic average of the measured values of the time of appearance of the characteristic points of the received signal, only those measured values of the time of appearance of the characteristic points of the received signal are used, which are obtained at the clock intervals of the signal with a single characteristic point.

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