Ground-penetrating radar device

Abstract

To provide a ground penetrating radar device capable of generating B scope data in shortening the acquisition time of an A scope signal while suppressing an influence on depth accuracy and resolution characteristics.SOLUTION: A ground penetrating radar device includes: a transmitter 23 that transmits electromagnetic waves for exploration into the ground; a reference signal generation unit 18 that generates a reference signal corresponding to the electromagnetic waves; a timing control unit 11 that controls the transmitter and the reference signal generation unit; a receiver 24 that receives electromagnetic waves reflected in the ground; and a processing device 10 that processes an A scope signal output from the receiver. The timing control unit controls the operating timing of the transmitter and the reference signal generation unit to change the sampling interval and reference timing of the A scope signal, and the processing device performs interpolation processing to generate B scope data.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a ground-penetrating radar device that irradiates electromagnetic waves into the ground and measures the reflected waves to detect buried objects and internal structures. [Background technology]

[0002] Conventionally, the sampler method has been widely used as a receiving circuit method for underground radar devices (see, for example, Patent Document 1). In this method, short-duration pulse or burst radar received signals are received as time-expanded similar waveforms.

[0003] With the sampler method, the acquisition of one A-scope signal (point measurement information) is determined by the number of sampling points and the repetition time interval of the reference signal. For example, if you try to sample 100 points of a 100 ns radar signal in real time at 1 ns intervals, and the repetition time interval of the reference signal is 1 μs, it will take 100 ns / 1 ns x 1 μs = 100 μs. In addition, the timing for acquiring the A-scope signal is generally triggered by the distance traveled by the radar. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2020-024163 Summary of the Invention [Problem to be solved by the invention]

[0005] By the way, usually, the time Ta for acquiring one A-scope signal is designed to be sufficiently short compared with the radar movement trigger generation interval Td (Ta <Td)。 However, the repetition time of the reference signal generally has a relatively low degree of freedom in setting it because it affects the radar's output power and reception sensitivity. Furthermore, as the radar's movement trigger interval becomes shorter, for example when the radar is mounted on a vehicle and traveling, there is a possibility that "Ta > Td" will occur.

[0006] In order to reduce the number of sampling points without changing the range of the depth axis (time axis), it is possible to increase the sampling interval, but this would sacrifice depth accuracy and resolution. For this reason, a method is needed to further reduce the acquisition time of the A-scope signal while minimizing the impact on characteristics.

[0007] The present invention has been made in consideration of the above circumstances, and its purpose is to provide an underground radar device that can shorten the acquisition time of an A-scope signal and generate B-scope data while suppressing the impact on depth accuracy and resolution characteristics. [Means for solving the problem]

[0008] An underground radar device according to one aspect of the present invention includes a transmitter that transmits electromagnetic waves for exploration underground, a reference signal generating unit that generates a reference signal corresponding to the electromagnetic waves, a timing control unit that controls the transmitter and the reference signal generating unit, a receiver that receives the electromagnetic waves reflected underground, and a processing unit that processes an A-scope signal output from the receiver, wherein the timing control unit controls the operation timing of the transmitter and the reference signal generating unit to change the sampling interval and reference timing of the A-scope signal, and the processing unit performs interpolation processing to generate B-scope data. [Effects of the Invention]

[0009] In this invention, the sampling points are thinned out to shorten the acquisition time of the A-scope signal, and missing data is estimated by interpolation processing using adjacent data in the direction of the movement axis, thereby minimizing the impact on depth accuracy and resolution characteristics and generating B-scope data. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a block diagram showing a schematic configuration of an underground radar device according to an embodiment of the present invention; [Figure 2]FIG. 10 is a schematic diagram showing a reference example of the relationship between the depth of a sampling point and the moving distance in a conventional underground radar device. [Figure 3] FIG. 2 is a schematic diagram showing the relationship between the depth of the sampling point and the moving distance in the underground radar device shown in FIG. 1, in the case where the sampling is alternately shifted. [Figure 4] FIG. 2 is a schematic diagram showing the relationship between the depth of the sampling point and the moving distance in the underground radar device shown in FIG. 1, in which the amount of thinning is changed depending on the depth. [Figure 5] FIG. 2 is a schematic diagram showing the relationship between the depth of the sampling point and the moving distance in the underground radar device shown in FIG. 1, in which the sampling point is shifted for each depth. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Fig. 1 shows a schematic configuration of an underground radar device according to an embodiment of the present invention. This underground radar device is mounted on a mobile object such as a cart with wheels and a drive mechanism, and performs underground exploration while moving.

[0012] That is, the processing device 10 includes a timing control unit 11, a correlation processing unit 12, an A / D processing unit 13, and an interpolation processing unit 14. Specifically, it is configured by, for example, a personal computer equipped with an underground exploration program, and the user can observe the measurement results on a display unit 15 such as an LCD monitor, and can also set various measurement parameters, set conditions related to signal processing, select a data processing method for displaying the measurement results, and so on by operating an input unit 16 such as an operation panel or keyboard.

[0013] The timing control unit 11 controls the operation timing of a Tx signal generating unit 17 that generates a transmission signal for exploration, and a Lo signal generating unit 18 that generates a reference signal. The transmission signal generated by the Tx signal generator 17 is input to the transmission amplifier 19, where it is amplified, and then transmitted into the ground from the transmission antenna 20. The Tx signal generator 17, transmission amplifier 19, and transmission antenna 20 function as a transmitter 23 of electromagnetic waves for exploration.

[0014] The waves reflected from the ground are received by the receiving antenna 21, and the received signal is amplified by the receiving amplifier section 22. The receiving antenna 21 and the receiving amplifier section 22 function as part of a receiver 24 that receives the electromagnetic waves reflected from the ground.

[0015] The received signal amplified by the receiving amplifier unit 22 and the reference signal generated by the Lo signal generator unit 18 are input to the correlation processor unit 12, where they are correlated. The output of the correlation processor unit 12 is input to the A / D processor unit 13, where it is analog-to-digital converted, and then input as a sampling signal to the interpolation processor unit 14. The interpolation processor unit 14 performs two-dimensional interpolation processing based on the acquired sampling signal, and the interpolated A-scope signal is displayed on the display unit 15.

[0016] An A-scope signal is a waveform pattern that represents the received strength of a detection signal obtained by exploration at a specific measurement point as a function of the delay time or reflection time elapsed from the transmission of the radio wave to its reception. Furthermore, B-scope data (path cross-section measurement information) is a chart that represents the received strength of a detection signal as a function of the delay time and the travel distance. Specifically, an A-scope signal is an intensity waveform that represents the intensity distribution of a detection signal, with one axis representing the reflection time (or the distance in the depth direction) and the other axis representing the signal strength. Furthermore, B-scope data is two-dimensional image data that displays the intensity distribution of a detection signal collected at multiple measurement points along the travel path of a moving object as a two-dimensional intensity distribution consisting of a function of position in two axial directions, with one axis representing the reflection time (or the distance in the depth direction) and the other axis representing the distance in the path direction.

[0017] As a reference example, Figure 2 shows the relationship between the depth of sampling points and the distance traveled in a conventional underground radar device. Here, circles represent sampling points, and the group of samples enclosed by a dashed line 30 is called the A-scope. Because the underground radar device is moving, there is a discrepancy in the position information between the start and end of sampling, but this error is so small that it can be ignored.

[0018] When the underground radar device moves a predetermined distance, a trigger is generated from the timing control unit 11, and A-scan measurements are performed in conjunction with this trigger. When the underground radar device moves as shown by the horizontal arrow, a group of samples (A-scans) with increasing depth from the trigger are obtained. By repeating this sampling operation, the intensity distribution of the detection signals collected at many measurement points is expressed as a function of position in two axial directions, and two-dimensional image data is displayed on the display unit 15. The operator can then use the image data to search for buried objects and internal structures underground. In this case, if the depth is N and the distance is M, then the required measurement time is "N x M x dt."

[0019] Figure 3 shows the relationship between the depth of sampling points and the distance traveled in the underground radar device shown in Figure 1. Here, circles represent sampling points, and black circles represent points estimated by interpolation from surrounding sampling points. The group of samples enclosed by a dashed line 30 is called the A-scope. Furthermore, because the underground radar device is moving, there is a discrepancy in the position information between the start and end of sampling, but this error is so small that it can be ignored.

[0020] As shown in Figure 3, sampling is performed on the time axis (depth axis direction) of the A-scope at intervals (2Ts) that are twice the desired sampling interval (Ts). Furthermore, for the next A-scope (adjacent in the movement axis direction), sampling is performed at a timing shifted by the initial sampling interval (Ts). This is performed sequentially to alternately shift the sampling points and acquire data in a so-called checkerboard pattern. After that, when generating B-scope data (image), two-dimensional interpolation processing is performed by the interpolation processing unit 14 to estimate the values ​​of the missing points.

[0021] In this way, by sampling by thinning out the sampling points so that they alternate, the measurement time becomes "(N / 2) × M × dt", which is essentially half the time compared to the sampling shown in Figure 2. Furthermore, even if the number of samples is reduced to shorten the time required to acquire the A-scope signal, by using data obtained by two-dimensionally interpolating the signal components necessary for depth accuracy and resolution from adjacent sampling points, B-scope data can be generated from data with the same number of samples as shown in Figure 2, thereby minimizing the adverse effects on depth accuracy and resolution characteristics.

[0022] <Variation 1> FIG. 4 shows the relationship between the depth of sampling points and the distance traveled in the underground radar device shown in FIG. 1, and the amount of thinning out varies depending on the depth. In this first modification, the sampling interval is increased toward the latter half of the time axis (depth axis) of the A-scope. That is, sampling is performed at intervals twice as long (2Ts) and three times as long (3Ts) as the desired sampling interval (Ts). After acquiring the data, the interpolation processing unit 14 performs an interpolation process when generating B-scope data (image) to estimate the values ​​of missing points (points marked with a black circle). In this interpolation process, linear interpolation is performed using sampling points adjacent in the depth direction.

[0023] In this way, in this first modification, the sampling interval is changed for each depth by utilizing the characteristic of underground radar that only low frequencies penetrate deep into the ground. Specifically, sampling in shallow areas underground is not thinned out, but sampling in deep areas underground is thinned out. Since underground radar signals have the characteristic that only low frequency components are included (high frequencies are attenuated) in the latter half of the time axis (deep depth), it is possible to perform interpolation processing while maintaining the necessary frequency components.

[0024] <Variation 2> Fig. 5 shows the relationship between the depth of the sampling points and the distance traveled in the underground radar device shown in Fig. 1, in which the sampling points are shifted for each depth. This second modification combines the two methods described above, acquiring data by sampling points in a checkerboard pattern with the sampling interval increasing as the depth increases. After acquiring data for each sampling point, when generating B-scope data (image), the interpolation processor 14 performs two-dimensional interpolation to estimate the values ​​of missing points (points marked with a black circle). Of course, this interpolation may be performed using only the A-scope.

[0025] In this way, by combining the two sampling methods, further time reduction effects can be expected. Furthermore, even if the number of samples is reduced to shorten the time required to acquire the A-scope signal, the signal components required for depth accuracy and resolution are interpolated from adjacent sampling points, and only low-frequency components are included at deep depths, so adverse effects on depth accuracy and resolution characteristics can be minimized.

[0026] The configurations, sampling procedures, etc. described in the above embodiment and modifications 1 and 2 are merely outlined to enable the present invention to be understood and practiced. Therefore, the present invention is not limited to the described embodiment, and can be modified in various forms without departing from the scope of the technical idea set forth in the claims. [Explanation of symbols]

[0027] 10...processing device, 11...timing control section, 12...correlation processing section, 13...A / D processing section, 14...interpolation processing section, 15...display section, 16...input section, 17...Tx signal generating section (transmitting signal generating section), 18...Lo signal generating section (reference signal generating section), 19...transmitting amplifier section, 20...transmitting antenna, 21...receiving antenna, 22...receiving amplifier section, 23...transmitter, 24...receiver

Claims

1. a transmitter that transmits electromagnetic waves for exploration underground; a reference signal generating unit that generates a reference signal corresponding to the electromagnetic wave; a timing control unit that controls the transmitter and the reference signal generating unit; a receiver that receives electromagnetic waves reflected from the ground; a processor for processing an A-scope signal output from the receiver, The timing control unit controls the operation timing of the transmitter and the reference signal generating unit to change the sampling interval and reference timing of the A-scope signal, and the processing unit performs interpolation processing to generate B-scope data.

2. 2. The underground radar device according to claim 1, wherein the processing device comprises: a correlation processing unit that processes the correlation between the A-scope signal from the receiver and the reference signal from the reference signal generating unit; an A / D processing unit that performs analog / digital conversion on the output signal of the correlation processing unit; and an interpolation processing unit that generates B-scope data by interpolating the sampling signal output from the A / D processing unit.

3. the timing control unit controls the reference signal generating unit to input sampling signals to the interpolation processing unit at intervals twice the predetermined sampling interval with respect to the depth axis of the A-scope signal, and inputs sampling signals for A-scope signals adjacent in the direction of the movement axis at timings alternately shifted by the sampling interval; 3. The underground radar device according to claim 2, wherein the interpolation processing unit performs two-dimensional interpolation processing to estimate values ​​of missing points when generating B-scope data.

4. the timing control unit controls the reference signal generating unit to input to the interpolation processing unit a sampling signal whose sampling interval increases as the depth increases on the depth axis of the A-scope; 3. The underground radar device according to claim 2, wherein the interpolation processing unit generates B-scope data by performing interpolation processing on the A-scope signal.

5. 3. The underground radar device according to claim 2, wherein the interpolation processing unit estimates values ​​of missing points by performing two-dimensional interpolation processing when generating B-scope data.

6. the timing control unit controls the reference signal generating unit to input sampling signals to the interpolation processing unit at intervals twice the predetermined sampling interval with respect to the depth axis of the A-scope signal, the sampling interval being increased as the depth becomes deeper, and inputs sampling signals for A-scope signals adjacent in the direction of the movement axis at timings alternately shifted by the sampling interval; 3. The underground radar device according to claim 2, wherein the interpolation processing unit performs interpolation processing on the A-scope signal, and performs two-dimensional interpolation processing when generating B-scope data to estimate values ​​of missing points.

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