JP2018100944A - Chirp type multi-ground radar system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an underground radar system capable of increasing the depth of exploration while maintaining the resolution of detected target.SOLUTION: A multi-radar system uses multiple chirped underground radars at the same place. The multi-radar system employs a method in which each radar manages time band to send and receive to prevent neighboring antennas from interfering each other even when plural radar systems are used simultaneously. Since the chirp wave is a long pulse wave in which the transmission signal is transmitted for a long time and high output can be obtained, the depth of exploration can be increased. A pulse compression circuit is adopted in the receiving circuit for converting to impulse to improve the resolution.SELECTED DRAWING: Figure 6

Description

  The present invention relates to a ground penetrating radar system. In particular, the present invention relates to a ground penetrating radar system having a high resolution and a deep search depth.

  In the past, a road may have a cavity in the basement, resulting in an accident such as a depression. Among the cavities generated in the basement, a method using a ground penetrating radar system using electromagnetic waves in the microwave band is known as a technique for finding a cavity that may lead to an accident in the future. Typical methods include a pulse method, an FMCW method, a continuous wave method, a chirp method, an encoding method, and the like, each having a characteristic in exploration ability.

  In the case of exploration by the ground penetrating radar system, a ground penetrating radar pushed by a hand may be used. When exploring roads with ground penetrating radars that are pushed by hand, it is necessary to temporarily block general traffic for exploration.

  Therefore, in recent years, exploration techniques for ground penetrating radar systems pulled by vehicles that do not hinder traffic have been implemented.

  Various proposals have conventionally been made for the exploration technique using the ground penetrating radar system and the radar apparatus and system employed therein (Patent Documents 1 and 2 and Non-Patent Document 1).

  When exploring roads and the like with a pulsed ground penetrating radar, for example, if the exploration area width of the road is 2.5 m, the antenna size installed in the ground penetrating radar is generally 0.5 m square. Therefore, it is necessary to search the 5-side line round-trip or 5 times one way.

  Since conventional ground penetrating radar is generally a hand-held type, if a distance of 100 m is also used for one-sided line search, a time of about 3 minutes one way is required at a speed of 4 km / h. On the 5-side line, even if it is considered to carry out round trips, it takes at least 30 minutes of exploration time. Therefore, a plurality of pulse type ground penetrating antennas are arranged in the crossing direction of the road and mounted on the towing cart, and road surface exploration is performed by running the vehicle.

  In the conventional pulse-type ground penetrating radar, the transmission output is weak because the width of the pulse to be transmitted in a certain repetition period is several nanoseconds. This limits the depth of exploration capability.

  Here, if the pulse output is widened to increase the transmission output, the resolution of the detection target corresponding to the widened portion is deteriorated.

  For this reason, the pulse type ground penetrating radar has a limit in depth and resolution that can be probed in principle.

JP 2002-82162 A JP 2009-58308 A

IEICE Transactions B Vol.J83-B No.1 pp113-120 "Chirp signal pulse compression ground penetrating radar using delay correlator" (Yoshiyuki Serizawa, Yasuo Arai)

  Provided is a ground penetrating radar system capable of increasing the exploration depth while maintaining the resolution of a detection target.

[1]
A chirped multi-ground radar system comprising a plurality of radar devices equipped with a chirped ground penetrating radar antenna and receiving a reflected signal in the ground and performing a search,
Each transmission signal for transmission from the chirped underground radar antenna of each of the radar devices is shifted by a predetermined interval, and
A chirped multi-ground radar system in which reception signals acquired by individual radar devices are shifted by a predetermined interval in synchronization with the transmission signals.

[2]
[1] The chirped multi-ground radar system according to [1], wherein the receiving circuit includes a pulse compression circuit that converts a chirped pulse wave into an impulse.

[3]
A chirped multi-ground radar system comprising a plurality of radar devices equipped with a chirped ground penetrating radar antenna and receiving a reflected signal in the ground and performing a search,
The transmission signal output is always performed by only one antenna among the plurality of radars, and the reflected signal from the underground is received by the antennas of all other radars.
The transmission signals are output by the plurality of radar devices by sequentially switching the antenna that performs the transmission signal output from the one antenna to the remaining other antennas at predetermined intervals. A chirped multi-ground radar system that obtains received data from all other antennas that have output.

[4]
[3] The chirped multi-ground radar system according to [3], wherein the receiving circuit includes a pulse compression circuit for converting a chirped pulse wave into an impulse.

  According to the present invention, it is possible to provide a ground penetrating radar system capable of increasing the search depth while maintaining the resolution of the detected target.

The figure showing an example of the frequency control waveform in one embodiment of the present invention. The figure showing an example of the chirp waveform of the transmission signal in one embodiment of the present invention. The figure showing an example of "frequency" versus "delay control waveform" which controls the delay circuit in one embodiment of the present invention. The figure showing an example of the pulse compression waveform in one embodiment of the present invention. FIG. 4 is a diagram illustrating an example of a configuration of a pulse compression circuit using a delay circuit controlled by “frequency” versus “delay control waveform” illustrated in FIG. 3. The figure explaining an example of the outline of composition of the chirp type radar in one embodiment of the present invention. 1 is an example of a block diagram of a chirped radar according to an embodiment of the present invention. The figure showing an example of the sampling pulse in one Embodiment of this invention. BRIEF DESCRIPTION OF THE DRAWINGS The figure explaining an example of a structure outline | summary of the chirp-type multi-ground radar system in one Embodiment of this invention. The figure explaining the timing control of the multi-radar trigger pulse control waveform used for shifting the signal time from each radar apparatus by predetermined short time in all radar simultaneous synchronous management systems. The figure showing an example of the antenna arrangement | sequence in embodiment shown in FIG. The figure explaining the principle of pulse compression using delay correlation. The figure showing an example of a timing in case a delay correlator is used for the pulse compression which converts the pulse wave with a long chirp wave into an impulse in a receiving circuit. The figure explaining the state in which the transmission signal is performed only from one radar and reception is performed by all other radars in the all radar simultaneous synchronization management method. FIG. 15 is a diagram illustrating a state in which a transmission signal is performed only from one other radar and reception is performed by all other radars following the state illustrated in FIG. 14 in the all-radar simultaneous synchronization management method.

  In this embodiment, a chirped ground penetrating radar is employed to increase the exploration depth while maintaining the resolution of the detected target.

  In the chirp radar, the chirp signal generated by the chirp signal generator is frequency-converted and amplified, and a pulsed transmission wave is transmitted from the antenna. Target (detected target), for example, a reflected wave reflected by an embedded object or a boundary surface with different relative permittivity or conductivity is received by an antenna, converted, amplified, and sampled based on sampled radar received data (Detected target), for example, a buried object or a boundary surface with different relative permittivity or conductivity is detected.

  The principle of the chirped ground penetrating radar will be described as follows.

  The chirp waveform of the transmission signal is a long pulse wave obtained by FM-modulating the carrier signal as shown in FIG. 2 according to the frequency control waveform shown in FIG. As shown in FIG. 1, the frequency changes linearly with time.

  Since such a chirp wave transmits a transmission signal for a long time, a high output can be obtained and the exploration depth can be increased.

  In this embodiment, since this pulse wave is a long pulse wave, a mechanism for converting it into an impulse in the receiving circuit is employed in order to improve the resolution.

  In the present embodiment, a mechanism for converting into an impulse in the receiving circuit is called a pulse compression circuit.

  As an example, FIG. 5 shows a configuration of a pulse compression circuit using a delay circuit controlled by the frequency versus delay control waveform shown in FIG. By passing the received chirp signal through this compression circuit, the pulse compression waveform shown in FIG. 4 is obtained.

  Since the chirped pulse wave is a long pulse wave, in order to improve the resolution, the pulse compression method for converting into an impulse in the receiving circuit includes a method using a SAW device in addition to the method shown in FIG. It is also possible to adopt a system in which pulse compression is performed by digital processing or the delay correlation circuit shown in FIG.

  For example, as shown in an example of timing in FIG. 13, a delay correlator may be used for pulse compression for converting a pulse wave having a long chirp wave into an impulse in the receiving circuit.

  By compressing the chirp signal by any of the methods described above, a ground penetrating radar system with a high resolution and a deep search depth is realized.

  By using any one of the pulse compression methods described above, a narrow impulse equivalent to or higher than that of the conventional pulsed underground radar can be obtained. Therefore, it is possible to maintain the resolution of a detection target, for example, an embedded object, or a boundary surface having different relative permittivity or conductivity.

  Thereby, compared with the conventional pulse type ground penetrating radar, it is possible to obtain an increase in the exploration depth corresponding to the increased pulse width.

  FIG. 6 shows an example of an embodiment of a chirped subsurface radar realized based on the above-described principle.

  FIG. 7 is a block diagram showing an example of a chirped ground penetrating radar according to this embodiment.

  Here, in accordance with the trigger pulse input from the timing circuit, a chirp waveform shown in FIG. 2 is generated by the chirp generation circuit, and power is supplied to the broadband transmission antenna through the transmission circuit and the balun transformer.

  The chirp wave radiated into the ground is reflected when there is an embedded object or an interface having different relative permittivity or conductivity, and the reflected wave is received by the broadband receiving antenna.

  This received signal passes through a balun transformer, is amplified by an RF receiving circuit, and is expanded to a low frequency signal waveform by a sample and hold circuit.

  As an example, the 125 ns time region is expanded 10,000 times to 1.25 ms.

  As this expansion method, the sampling pulse input from the timing circuit is input by sequentially shifting by t = 0.1 ns with respect to the period T of the trigger pulse as shown in FIG. 8, and the chirp waveform of the received signal is sampled and held. A scheme can be adopted.

  By this operation, a low frequency chirp signal having a waveform similar to the high frequency is obtained.

  This low frequency chirp signal is input from the variable gain circuit to the pulse compression circuit described above to obtain the pulse signal shown in FIG.

  By treating this as a received signal of the radar system, a high-resolution underground radar system can be realized by deep exploration.

  In this embodiment, since the transmission signal is transmitted for a long time, a high output can be obtained and the chirp wave that can increase the exploration depth is a long pulse wave. The resolution is improved by adopting.

  In this embodiment, the chirped ground penetrating radar as described above is employed, and a plurality of ground penetrating antennas are arranged in the crossing direction of the road and mounted on the towing cart, thereby enabling road surface cavity exploration by vehicle travel. A system was built.

  Here, since a normal chirped ground penetrating radar uses a continuous signal for a long time, the time side lobe has a long tail when the chirp signal waveform is converted into a pulse waveform. This interferes with the weak signal of the received signal and lowers the search capability.

  Therefore, in the present embodiment, the reflected wave from the ground surface and the target (detected target), for example, the reflected wave from the buried object or the boundary surface with different relative permittivity or conductivity are not overlapped as much as possible. A short chirp type ground penetrating radar that can improve the detection of weak signals by using a short chirp signal of several tens of nanoseconds is adopted.

  In this embodiment, a plurality of short chirp radars based on this method are used, and the underground information necessary for a short time can be obtained.

  Here, when a plurality of radar systems are used at the same place at the same time, interference occurs in the received signal between adjacent antennas. This interference lowers the search performance, so that unless the interference is removed, the advantage of obtaining a plurality of search data reception signals simultaneously using a plurality of radar systems is not exhibited.

  When a plurality of radar systems are used simultaneously at the same location, interference occurs in the received signal between adjacent antennas. This embodiment makes it possible to eliminate this interference.

  For example, even if multiple radar systems are used at the same place at the same time, a system that manages the time zone transmitted and received by each radar is used to prevent interference between the received signals at adjacent antennas. Yes.

  As a result, even when multiple radar systems are used simultaneously at the same location, the radar operates without interference between adjacent antennas, and a high-resolution ground reflection signal can be obtained. I made it.

  In this embodiment, the following is adopted as a method for managing the time zone (timing) transmitted and received by each radar in a plurality of deployed radars, thereby realizing a chirped multi-ground radar system.

  In this embodiment, this problem is solved by adopting an all-radar simultaneous synchronization management method described below or an all-receiving antenna operation method by sequentially transmitting antenna switching.

All-radar simultaneous synchronization management method This is a method for managing the operation timing of all the radars used in plurality.

  In a system that receives a reflected signal in the ground by using a plurality of chirped underground radar antennas, in order to avoid interference between the received signals, the signal time of each radar device is shifted by a predetermined short time and transmitted. For example, it is a chirp radar system composed of a plurality of radars, wherein transmission is performed at intervals of 125 ns, and at the same time the sampling trigger position of the reception circuit is shifted according to the transmission trigger for shifting the time of the transmission signal as described above.

  In order to prevent each radar in a plurality of radars constituting a chirped multi-ground radar system from operating at exactly the same timing, for example, signals of individual radar devices can be controlled by timing control using a predetermined multi-radar trigger pulse control waveform. The operation is performed by shifting the time by a predetermined short time, for example, 125 ns. In synchronization with this transmission timing, the sampling pulse of the receiving circuit is also shifted by a predetermined short time, for example, 125 ns in each radar device. As a result, the reception timing of the reception signal is shifted by a predetermined short time, for example, 125 ns in synchronization with each transmission signal.

  In this way, interference between received signals can be avoided.

  In the case of this all-radar simultaneous synchronization management method, the operating time of each radar device is shifted by a predetermined short time, for example, by 125 ns, so that interference of the received signals of each radar is avoided.

  By adopting this method, even if a plurality of radars are brought close to each other and operated in the same place, the high detection capability of the chirped subsurface radar can be obtained without interference.

All-receiver antenna operation method by sequentially switching transmit antennas In a system that uses multiple chirped ground penetrating radar antennas to receive reflected signals in the ground, the transmit signal is always sent to one antenna in order to avoid interference between the received signals. In the multiple radar system, the reflected signal from the basement is received by all other antennas, and the antenna that outputs the transmission signal is sequentially switched, and the received signal is always received by all other receiving antennas accordingly. This is a chirp radar system configured.

  In a plurality of radars constituting the chirped multi-ground radar system, transmission is always performed by only one antenna, and at that time, all other remaining radars transmit signals transmitted by the one antenna. The time when the one antenna transmits is set to a predetermined short time, for example, 1.25 ms, and the short time interval, for example, 1.25 ms (1250 samplings). Then, the radar that performs the transmission is sequentially changed from the one radar to any of the remaining radars. By sequentially repeating this, all received data can be obtained by a plurality of radar devices.

  As a result, it is possible to prevent interference generated when a plurality of ground penetrating radars are arranged to perform underground exploration.

  In the case of this all-reception antenna operation method by sequential transmission antenna switching, when one radar is transmitting, all other radars receive the received signal, but the transmission signal is transmitted from only one radar. Therefore, the received signal does not interfere.

  By adopting this method, even if a plurality of radars are brought close to each other and operated in the same place, the high detection capability of the chirped subsurface radar can be obtained without interference.

Combined method Combines the above-mentioned all-radar simultaneous synchronization management method and the all-receiver antenna operation method by sequentially switching transmission antennas, and operates the receiving circuit of the radar device that stops transmission at the same time as transmitting and receiving with any plurality of radar devices A chirp radar system composed of a plurality of radars.

  In this way, even if a plurality of radars are brought close to each other and operated in the same place, the high detection capability of the chirped subsurface radar can be obtained without interference.

  As described above, the present invention relates to a ground penetrating radar apparatus. This is a chirped subsurface radar system, which is a chirped subsurface radar system with an increase in transmission power without degradation of minimum detection distance and resolution.

  This is a ground penetrating radar system that can simultaneously receive a plurality of received data by using a pulse compression radar circuit that enables the maximum detection distance to be expanded and the distance resolution to be improved.

  In the present invention, a multi-radar system using a chirp method and using a plurality of radars is employed. That is, a multi-radar system in which a plurality of chirped ground penetrating radars can be used at the same place is employed.

  FIG. 9 shows an example of a chirped multi-ground radar system according to an embodiment of the present invention.

  An example of the antenna arrangement in this case is shown in FIG.

  In the embodiment shown in FIG. 11, a cart that can be pulled by a vehicle that can mount eight sets of ground penetrating radar devices is used. Here, in order to grasp in detail the inside of the road, seven small radars and one medium radar are arranged as shown in FIG. 11 in order to search a deeper depth.

  At this time, from the arrangement shown in FIG. 11, the antennas of the seven small radars can be slid in the road width direction so that the exploration enters the range of the road width of 2.5 m, and can search for any width of 2 m to 2.5 m. I am doing so.

  In this embodiment, an all-radar simultaneous synchronization management system that manages the timings at which all radars operate is employed.

  Based on the timing control of the multi-radar trigger pulse control waveform shown in FIG. 10, each radar was operated by shifting by 125 ns so as not to operate at the same timing.

  In synchronization with this transmission timing, the sampling pulse shown in FIG. 8 is also operated by shifting each of the radar devices by 125 ns.

  With this operation, the reception signal is also shifted by 125 ns in synchronization with each transmission signal.

  This solves the problem that when a plurality of antennas are arranged as shown in FIG. 11, the neighboring antennas interfere with each other, and unnecessary signals are generated to reduce the original search capability.

  Similar to the first embodiment, the cart can be pulled by a vehicle on which eight sets of ground penetrating radar devices can be mounted. Here, in order to grasp in detail the inside of the road, seven small radars and one medium radar are arranged as shown in FIG. 11 in order to search a deeper depth.

  At this time, from the arrangement shown in FIG. 11, the antennas of the seven small radars can be slid in the road width direction so that the exploration enters the range of the road width of 2.5 m, and can search for any width of 2 m to 2.5 m. I am doing so.

  In this embodiment, an all-receiver antenna operation system by sequentially switching transmit antennas is adopted.

  In the form shown in FIG. 14, the transmission radar was sequentially changed at intervals of 1.25 ms (1250 samplings).

  In FIG. 14, only the transmission antenna of the small radar 1 transmits, and all the other small radars operate only the reception function. In FIG. 15, only the transmission antenna of the small radar 2 transmits, and all the other radars operate only with the reception function.

  By sequentially repeating this at intervals of 1.25 ms, it is possible to obtain all received data with a plurality of radar devices.

  As a result, it is possible to prevent interference generated when a plurality of ground penetrating radars are arranged to perform underground exploration.

  The embodiments and examples of the present invention have been described with reference to the accompanying drawings. However, the present invention is not limited to these, and various modifications can be made within the technical scope grasped from the description of the claims. is there.

Claims (4)

A chirped multi-ground radar system comprising a plurality of radar devices equipped with a chirped ground penetrating radar antenna and receiving a reflected signal in the ground and performing a search,
Each transmission signal for transmission from the chirped underground radar antenna of each of the radar devices is shifted by a predetermined interval, and
A chirped multi-ground radar system in which reception signals acquired by individual radar devices are shifted by a predetermined interval in synchronization with the transmission signals.   2. The chirped multi-ground radar system according to claim 1, wherein the receiving circuit includes a pulse compression circuit that converts a chirped pulse wave into an impulse. A chirped multi-ground radar system comprising a plurality of radar devices equipped with a chirped ground penetrating radar antenna and receiving a reflected signal in the ground and performing a search,
The transmission signal output is always performed by only one antenna among the plurality of radars, and the reflected signal from the underground is received by the antennas of all other radars.
The transmission signals are output by the plurality of radar devices by sequentially switching the antenna that performs the transmission signal output from the one antenna to the remaining other antennas at predetermined intervals. A chirped multi-ground radar system that obtains received data from all other antennas that have output.   4. The chirped multi-ground radar system according to claim 3, wherein the receiving circuit includes a pulse compression circuit that converts a pulse wave of a chirp wave into an impulse.

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