JP7787683B2 - Ground-penetrating radar device - Google Patents

Description

The present invention relates to an underground radar device that irradiates electromagnetic waves into the ground and measures the reflected waves to detect buried objects and internal structures.

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

In 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. Furthermore, the timing of acquiring the A-scope signal is generally triggered by the distance traveled by the radar.

Japanese Patent Application Laid-Open No. 2020-024163

Incidentally, the time required for one A-scope signal acquisition operation Ta is usually designed to be sufficiently short compared with the radar movement trigger generation interval Td (Ta<Td).
However, the repetition time of the reference signal has a relatively low degree of freedom in setting it because it affects the output power and reception sensitivity of the radar. Furthermore, as the interval between radar movement triggers becomes shorter, for example, when the radar is mounted on a vehicle and traveling, there may be cases where "Ta >Td".

In this case, the following two types of operation are possible. The first is to interrupt subsequent sampling when the next movement trigger is input during acquisition of the A-scope signal, and to resume A-scope acquisition from the first sampling. The second is to continue acquisition of the A-scope signal even when the next movement trigger is input during acquisition of the A-scope signal, and to disable the trigger in question.
In either case, a loss of the search data occurs, which causes problems in generating B-scope data.

The present invention was made in consideration of the above circumstances, and its purpose is to provide an underground radar device that can ensure consistency between radar signals and the search position when moving at high speeds.

An underground radar device according to one aspect of the present invention comprises a transmitter that transmits electromagnetic waves for exploration underground, a receiver that receives the electromagnetic waves reflected underground, and a processing device that processes an A-scope signal output from the receiver, wherein the processing device randomly samples the A-scope signal from the receiver using position information as a trigger , assigns position information to each sampled data, and reconstructs the A-scope signal based on this position information.

In the present invention, information about radar movement and position is added to each point of sampling data of the A-scope signal, and the A-scope signal at a desired position is reconstructed based on this information. This makes it possible to generate exploration data (B-scope data) without any loss, regardless of the time required to acquire sampling data of the A-scope signal and the length of the trigger time interval due to the movement distance.
Therefore, according to the present invention, it is possible to provide an underground radar device that can ensure consistency between the radar signal and the search position when moving at high speed.

1 is a block diagram showing a schematic configuration of an underground radar device according to a first embodiment of the present invention; 2 is a flowchart showing the operation of a reconstruction processing unit in FIG. 1 . 2 is a schematic diagram showing the relationship between position information of sampling points and depth in the underground radar device shown in FIG. 1 . FIG. FIG. 10 is a schematic diagram showing, as a reference example, the relationship between the position information of the sampling point and the depth when the moving speed of the underground radar exceeds the limit. 2 is a schematic diagram for explaining the operation of the underground radar device shown in FIG. 1 . FIG. 1. FIG. 5 is a schematic diagram for explaining a modified example of the operation of the underground radar device shown in FIG. FIG. 10 is a block diagram showing a schematic configuration of an underground radar device according to a second embodiment of the present invention. FIG. 8 is a schematic diagram for explaining the operation of the underground radar device shown in FIG. 7 .

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

That is, the processing device 10 comprises a position information processing unit 11, a timing control unit 12, a correlation processing unit 13, an A/D processing unit 14, and a reconstruction processing unit 15. Specifically, it is configured, for example, by a personal computer equipped with an underground exploration program, and the user can observe the measurement results on the display unit 16, and can also operate the input unit 17 to set various measurement parameters, set conditions related to signal processing, select a data processing method for displaying the measurement results, etc.

The position information acquisition unit 18 is equipped with a GPS receiver (or encoder), a speedometer, an accelerometer, etc., and measures the exploration position, which is the measurement point, and outputs this as position information to the position information processing unit 11. The position information processing unit 11 processes this position information and outputs it to the timing control unit 12. The timing control unit 12 controls the operation timing of the Tx signal generation unit 19 and the Lo signal generation unit (reference signal generation unit) 20 based on the position information.

The transmission signal generated by the Tx signal generator 19 is input to the transmission amplifier 21, where it is amplified, and transmitted into the ground from the transmission antenna 22. The Tx signal generator 19, transmission amplifier 21, and transmission antenna 22 function as a transmitter of electromagnetic waves for exploration. Waves reflected from the ground are received by the receiving antenna 23, and the received signal is amplified by the receiving amplifier 24. The receiving antenna 23 and receiving amplifier 24 function as part of a receiver that receives electromagnetic waves reflected from the ground.

The received signal amplified by the receiving amplifier unit 24 and the reference signal generated by the Lo signal generator unit 20 are each input to the correlation processor unit 13, where they are correlated. The output of the correlation processor unit 13 is input to the A/D processor unit 14, where it is converted from analog to digital, and then input as a sampling signal to the reconstruction processor unit 15. The reconstruction processor unit 15 also receives the position information output from the timing controller unit 12, and the acquired sampling signal is compared with the position information to produce a reconstructed A-scope signal (point measurement information) that is displayed on the display unit 16.

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 between the transmission and reception of the radio wave. 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 delay time and travel distance. Specifically, an A-scope signal is an intensity waveform that represents the intensity distribution of a detection signal, with one axis representing reflection time (or distance in the depth direction) and the other axis representing 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 as a function of position in two axial directions, with one axis representing reflection time (or distance in the depth direction) and the other axis representing distance in the path direction.

Fig. 2 is a flowchart showing the operation of the reconstruction processing unit 15 in Fig. 1 to generate one line of radar. The reconstruction processing unit 15 acquires the sampling signal output from the A/D processing unit 14 (step S1) and compares it with the position information output from the timing control unit 12 (step S2).
In the next step S3, it is determined whether or not the predetermined number of samples has been acquired, and if it is determined that the number has been acquired, A-scope construction processing is carried out (step S4).

On the other hand, if it is determined in step S3 that the specified number of samples has not been obtained, it is determined whether the location information has changed (step S5), and if it is determined that the location information has changed, it is determined whether the number of samples required to configure the missing part has been obtained (step S6).
If it is determined that the required number of samples has been acquired, the process proceeds to step S4, where an A-scope configuration process is executed. If it is determined in step S5 that the position information has not changed, or if it is determined in step S6 that the required number of samples has not been acquired, the process returns to step S1, where a sampling signal is acquired.

Figure 3 shows the relationship between the position information of sampling points and depth in an underground radar device such as the one described above. Here, circles represent sampling points, and the group of samples enclosed by the dashed line is called the A-scope. Position information is associated with these sampling groups. Because the underground radar device moves, 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.

When the underground radar device moves a predetermined distance, a trigger is generated from the timing control unit 12, and A-scope measurements are taken in conjunction with this trigger. As the underground radar device moves as indicated by the horizontal arrow, a group of samples (A-scopes) with progressively deeper depths are obtained from the trigger.

Figure 4 shows an example of the relationship between sampling position information and depth when the underground radar's movement speed exceeds the limit. If a trigger for "Position = 2" occurs before the measurement for "Position = 1" is completed, the measurement for "Position = 1" will be interrupted, as indicated by the cross, and normal data will not be obtained.

Therefore, in this invention, the sampling operation for acquiring the A-scope signal is performed continuously, regardless of triggers caused by the movement of the underground radar device. Information regarding the movement (position) of the underground radar device is added to the data at each sampling point, and the position of the underground radar device is linked to each sampling data unit. The A-scope signal is then reconstructed based on the information added to the sampling points, according to the position interval required when generating the B-scope data.

At this time, if there is insufficient sampling data associated with the desired underground radar device position, the necessary data is generated by interpolating from sampling data associated with adjacent positions before and after it.

Figure 5 is a schematic diagram for explaining the operation of the underground radar device shown in Figure 1, and shows a specific example of the above explanation. First, provisional A-scope signals are continuously acquired at regular time intervals. At this time, position information is assigned to each sampling point. After that, the final A-scope signal is reconstructed based on the position information associated with each sampling point.

When the underground radar device moves in the direction of the arrow, a trigger is generated, and sampling operations for acquiring A-scope signals are performed continuously regardless of this trigger. That is, when a trigger occurs at time t1, sampling group 1 is acquired, when a trigger occurs at time t2, sampling group 2 is acquired, and when a trigger occurs at time t3, sampling group 3 is acquired. Similarly, when a trigger occurs at time t4, sampling group 4 is acquired, and when a trigger occurs at time t5, sampling group 5 is acquired.

Then, an A-scope signal is generated centered on the sampling group at "position 2," indicated by the two-dot chain line. If an A-scope signal cannot be generated using only the sampling at "position 2," data is interpolated (or estimated) from the surrounding areas. In Figure 5, data is missing from sampling points SP1 and SP2, indicated by the dashed line, so data is interpolated or estimated from the surrounding sampling points. The A-scope signal is then reconstructed based on the position information of each sampling point.

In this way, in an underground radar device using the sampler method, by adding information about the radar movement and position to each point of sampling data of the A-scope signal and reconstructing the A-scope signal at the desired position based on this information, it becomes possible to generate exploration data (B-scope data) without any loss, regardless of the relationship between the time for acquiring the A-scope sampling data and the length of the trigger time interval due to the movement distance.
Therefore, according to the present invention, it is possible to ensure consistency between the radar signal and the search position during high speed movement.

<Modification>
Fig. 6 shows a modified example of the operation of the underground radar device shown in Fig. 1. This modified example differs from the above-mentioned example in that the A-scope sampling groups are performed randomly rather than in chronological order along the time axis (depth axis). This is to prevent a decrease in the accuracy of the interpolation unit by preventing the loss of sampling points from becoming uniform.
However, data acquired within a certain acquisition time is uniform for each sampling point.

That is, as shown by the dashed-dotted line, A-scope sampling ("Time = 1," "Time = 2," "Time = 3," ...) is performed randomly, rather than in depth order. Then, as shown by the dashed-dotted line, an A-scope signal is generated centered around the sampling point at "Position = 2." If an A-scope cannot be generated using only sampling at "Position = 2," data is interpolated (or estimated) from the surrounding area.

In FIG. 6, data is missing at sampling points SP3 and SP4, so data is interpolated or estimated from surrounding sampling points, and the A-scan signal is reconstructed based on the position information of each sampling point.
Although not shown, random sampling at "position = 3" and "position = 4" also distributes the positions of missing data, preventing interpolation positions from concentrating at the same depth. This improves interpolation performance.

Second Embodiment
7 shows a schematic configuration of an underground radar device according to a second embodiment of the present invention, which includes multiple receiving circuits with different sampling points. The processing device 10' includes a position information processing unit 11, a timing control unit 12, a correlation processing unit 13-1, an A/D processing unit 14-1, a correlation processing unit 13-2, an A/D processing unit 14-2, and a reconstruction processing unit 15. Specifically, as in the first embodiment, the processing device 10' is configured with, for example, a personal computer running an underground exploration program. The user can observe the measurement results on the display unit 16, and can also operate the input unit 17 to set various measurement parameters, signal processing conditions, and select a data processing method for displaying the measurement results.

The position information acquisition unit 18 is equipped with a GPS receiver (or encoder), a speedometer, an accelerometer, etc., and measures the exploration position, which is the measurement point, and outputs the position information to the position information processing unit 11. The position information processing unit 11 processes this position information and outputs it to the timing control unit 12. The timing control unit 12 controls the operation timing of the Tx signal generation unit 19, Lo signal generation unit (reference signal generation unit) 20-1, and Lo signal generation unit (reference signal generation unit) 20-2 based on the position information.

The transmission signal generated by the Tx signal generator 19 is input to the transmission amplifier 21, where it is amplified, and transmitted into the ground from the transmission antenna 22. The Tx signal generator 19, transmission amplifier 21, and transmission antenna 22 function as a transmitter of electromagnetic waves for exploration. Waves reflected from the ground are received by the receiving antenna 23, and the received signal is amplified by the receiving amplifier 24. The receiving antenna 23 and receiving amplifier 24 function as part of a receiver that receives electromagnetic waves reflected from the ground.

The received signal amplified by the receiving amplifier unit 24 is input to the correlation processing unit 13-1 and the correlation processing unit 13-2. The correlation processing unit 13-1 calculates the correlation between the received signal input from the receiving amplifier unit 24 and the reference signal input from the Lo signal generating unit 20-1. The correlation processing unit 13-2 calculates the correlation between the received signal input from the receiving amplifier unit 24 and the reference signal input from the Lo signal generating unit 20-2. In this way, in the second embodiment, multiple receiving systems (first and second processing paths) with different sampling points are provided.

The output of the correlation processing unit 13-1 is input to the A/D processing unit 14-1, where it is converted from analog to digital, and then input to the reconstruction processing unit 15 as a sampling signal. The output of the correlation processing unit 13-2 is input to the A/D processing unit 14-2, where it is converted from analog to digital, and then input to the reconstruction processing unit 15 as a sampling signal. The reconstruction processing unit 15 receives the position information output from the timing control unit 12, and the acquired sampling signal is compared with the position information to display the reconstructed A-scope signal on the display unit 16.

Fig. 8 is a schematic diagram for explaining the operation of the underground radar device shown in Fig. 7. In the second embodiment, two sampling circuits for different depths are provided, and sampling is performed for each of the two systems.
In this way, even in an underground radar device having two paths of sampling circuits, by providing position information for each sampling, appropriate data generation and reconstruction becomes possible.

According to the second embodiment, not only can the consistency between the radar signal and the search position be ensured during high-speed movement, but it is also possible to generate search data (B-scope data) without any loss, regardless of the time required to acquire A-scope sampling data and the length of the trigger time interval due to the movement distance.
The division of the sampling points for each system may be performed in a group on the time axis (depth axis), or may be performed in an alternating manner.

The circuit configurations, operating procedures, etc. described in the first and second embodiments and variations above are merely schematic diagrams intended to enable the present invention to be understood and implemented. Therefore, the present invention is not limited to the described embodiments, and can be modified in various forms without departing from the scope of the technical concept set forth in the claims.

10, 10'... Processing device, 11... Position information processing unit, 12... Timing control unit, 13, 13-1, 13-2... Correlation processing unit, 14, 14-1, 14-2... A/D processing unit, 15... Reconstruction processing unit, 16... Display unit, 17... Input unit, 18... Position information acquisition unit, 19... Tx signal generation unit, 20, 20-1, 20-2... Lo signal generation unit (reference signal generation unit), 21... Transmitting amplifier unit, 22... Transmitting antenna, 23... Receiving antenna, 24... Receiving amplifier unit

Claims (5)

The system comprises a transmitter that transmits electromagnetic waves for exploration into the ground, a receiver that receives the electromagnetic waves reflected from the ground, and a processing device that processes an A-scope signal output from the receiver,
The processing device is characterized in that it randomly samples the A-scope signal from the receiver using position information as a trigger , assigns position information to each sampled data, and reconstructs the A-scope signal based on this position information. The system comprises a transmitter that transmits electromagnetic waves for exploration into the ground, a receiver that receives the electromagnetic waves reflected from the ground, and a processing device that processes an A-scope signal output from the receiver,
The processing device samples the A-scope signal from the receiver in time series at predetermined time intervals using the position information as a trigger , assigns position information to each sampled data, and reconstructs the A-scope signal based on this position information;
The processing device is characterized in that, when a trigger for A-scope signal acquisition based on the next position information occurs before the sampling triggered by the position information is completed, the processing device interpolates or estimates the missing sampling data from surrounding sampling data . 2. The underground radar device according to claim 1, wherein the processing device interpolates or estimates missing sampled data from surrounding sampled data when a trigger for A-scope signal acquisition based on the next position information occurs before the sampling triggered by the position information ends . The underground radar device described in claim 1, characterized in that the processing device samples the A-scope signal in first and second processing paths using the position information as a trigger. a reference signal generating unit that generates a reference signal corresponding to the electromagnetic wave for exploration;
a timing control unit that controls operation timings of the transmitter and the reference signal generation unit based on position information,
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 an output signal of the correlation processing unit; and a reconstruction processing unit that reconstructs the A-scope signal based on the sampling signal output from the A/D processing unit and the timing signal output from the timing control unit.