JPH1164510A - Radar type underground probe device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the weight and size by making a transmitter-receiver part for transmitting a pulse wave into the ground and receiving the reflected wave into an integrated form, and providing an interrupting part for the reflected signal of the transmitter-receiver part in a processing part for processing the reflected wave. SOLUTION: This device is formed of a transmitter-receiver unit 10, an amplifier part 20 and the like, and provided with an interrupting means 50 for controlling the flow of signal, between the transmitter-receiver part 10 and the amplifier part 20 between the both. A pulse generated by a first pulse generator 12 is emitted into the ground from a transmitting and receiving antenna 13c, and the reflected wave is also received by the transmitting and receiving antenna 13c, and transmitted to the lower side through a directional coupler 13a. In the interrupting means 50, a control pulse generated by a second pulse generator 52 is transmitted to a high frequency switch 51 with a delay of a prescribed time from the buildup of a transmitted trigger pulse, and the initial output from the transmitting and receiving part 13 is interrupted and removed by its opening and closing. Thus, signals are not saturated even if the amplifier 22 performs the amplification to the amplification ratio of the highest level, and a desired signal can be satisfactorily extracted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radar type underground exploration apparatus for exploring an underground object such as an underground gas conduit. Such a radar-type underground exploration device includes a transmitting / receiving unit that radiates a pulse wave generated at a predetermined repetition period into the ground and receives a reflected wave returned from the ground, and is received by the transmitting / receiving unit. The received reflected wave is sent to the reception signal processing unit, and the reception signal processing unit obtains a useful underground information signal with an amplification process.

[0002]

2. Description of the Related Art As a prior art of such a radar type underground exploration apparatus having such a configuration, one disclosed in JP-A-5-45444, "Method and Apparatus for Forming a Sectional Image of a Concealed Location" is disclosed in JP-A-48-79101. Some are disclosed in “Geological Survey Method”. In the former technique, a transmitting antenna and a receiving antenna are separately provided in a transmitting and receiving unit, and transmission of a pulse wave and reception of a received wave are performed by separate antennas. It is an effective method. On the other hand, the latter has an integrated transmission and reception configuration,
The transmitting / receiving unit is provided with a so-called directional coupler, an antenna, and the like, and constitutes this part.

[0003]

However, when the former transmission and reception are performed using separate antennas, the size of the apparatus becomes large, and it is difficult to operate the apparatus in a place where space is limited. Usually, a ferrite plate is attached to the entire inside of the antenna housing to prevent electromagnetic leakage from the antenna, but since the ferrite plate is heavy, the entire underground radar weighs 60 to 80 kg and must be carried alone. Is difficult. Further, to increase the depth of search, it is effective to increase the size of the antenna. However, in addition to the above-mentioned problems, there is a problem that if the area of the antenna section is increased, a space (dead zone) that cannot be searched on site increases.
Therefore, it is preferable to use a single antenna for both transmission and reception. Such a configuration is proposed by the latter technique described above, but this technique has the following problems. That is, in the case where the transmitting and receiving unit is integrated,
There is a problem that the signal pulse with a large amplitude is partially reflected at the entrance of the antenna and directly enters the reception signal processing unit, and the reception amplifier is saturated, and the weak reaction signal from the buried pipe cannot be properly amplified. There is no practical example yet. FIGS. 2 (c) and 3 (a) show states of signals transmitted to the reception signal processing section when such a transmission / reception integrated configuration is employed. In this example, the periodically generated pulse wave is as shown in FIG. As shown in FIG. 2C, in FIG. 2C, this signal is divided into a signal A having a relatively large amplitude in a time region close to the point of occurrence of the pulse wave and a signal region having a relatively large amplitude from the point of occurrence of the pulse wave. And a signal B having a relatively small amplitude. Here, the signal indicated by A is a wave directly reflected and returned from the transmission / reception unit in question. On the other hand, when the antenna structure of the transmitter and receiver is adopted, as shown in FIG. 3B, no large initial signal is recognized in A shown in FIG. In this respect, the separate transmission / reception type is preferred.

[0004] An object of the present invention is to adopt a transmission / reception integrated structure that can avoid an increase in the weight and size of the transmission / reception unit, and furthermore, a signal with amplification in a reception signal processing unit. An object of the present invention is to provide a radar-type underground exploration apparatus capable of performing good signal processing without causing saturation when performing processing.

[0005]

According to the present invention, there is provided a pulse generator which generates a pulse at a predetermined repetition period, receives a pulse wave from the pulse generator and radiates the pulse wave into the ground. A transmission / reception integrated transmission / reception unit for receiving the reflected wave returned from the ground, transmitting the reflected wave received by the transmission / reception unit to the reception signal processing unit, and amplifying the reception signal by the reception signal processing unit. A first characteristic configuration of the radar type underground exploration device that obtains a medium information signal is that a receiving signal processing unit includes a blocking unit that blocks a transmission / reception unit reflection signal, which is a reflection signal from the transmission / reception unit itself due to a pulse wave, from entering. Be prepared. In this configuration, the blocking unit blocks the transmission / reception unit reflection signal from entering the reception signal processing unit. Even when the reception signal processing unit performs processing with amplification, the amplitude is large. Since the transmission / reception unit reflection signal, which is unnecessary information, is removed, a necessary reflected wave from the ground can be extracted and satisfactory processing can be performed without causing a problem such as saturation.

A second characteristic configuration of the present application is the configuration of the above-described prerequisite, wherein a high-frequency switch is provided between the transmission / reception unit and the reception signal processing unit, and the high-frequency switch is used in the pulse generator. The present invention is provided with a blocking means for blocking a signal from entering the received signal processing unit in a predetermined time range from the point in time when the pulse wave is generated. The problem in the present application is a direct reflected signal from the transmitting / receiving unit. For example, when the transmitting / receiving unit is configured to include a directional coupler, a balun, an antenna, and the like, the direct signal from these devices is used. The reflected signal becomes a problem. Further, when it is desired to search for an object underground, the reflection from the ground surface should be removed. Here, when such a reflected wave is not interrupted, the received signal processing is performed at a point earlier than that in the ground (a time zone where a relatively short time has not elapsed from the point in time when the pulse wave is generated). Enter the department. Therefore, a high-frequency switch is provided between the transmission / reception unit and the reception signal processing unit, and a signal enters the reception signal processing unit within a predetermined time period from the point in time when the pulse wave is generated in the pulse generator by the high-frequency switch. If the shut-off means for shutting off is provided, when the shut-off is completed, the above-described directional coupler, balun, antenna,
Furthermore, ground surface reflection can be cut off and removed, and even if a process involving amplification is performed in the reception signal processing unit, the transmission / reception unit reflection signal which is unnecessary information having a large amplitude is removed. Therefore, it is possible to extract a necessary reflected wave from underground without causing a problem such as saturation and perform a good process.

Here, the time range in which the shut-off operation is performed by the shut-off means is defined as a time period from when the pulse wave is generated in the pulse generator to a time when the reflection from the antenna itself provided in the transmitting / receiving unit due to the pulse wave. It is preferable that the signal is in a time range until the antenna reflected signal, which is a signal, reaches the high-frequency switch. In this application, the direct reflected wave from the transmission / reception unit which travels to the received signal processing unit at the latest is a reflected wave from the antenna (mainly a direct reflected wave from the antenna end). Therefore, by blocking and removing the signal in the time domain up to this wave, a signal that is a major problem can be removed and the processing can be advanced.

Further, in such a configuration, the time zone in which the shut-off operation is performed by the shut-off means is defined as the time when the pulse wave is generated in the pulse generator as the start time of the shut-off operation.
It is preferable that the end time of the shutoff operation is variable. Even after the point at which the directly reflected signal from the transmission / reception unit reaches the reception signal processing unit, the residual wave remains,
There is a case where it is desired to remove the ground surface wave.Therefore, if the shut-off operation end time is configured to be variable, the shut-off operation end time is appropriately set according to the situation, and only necessary signals are taken out. Signal processing can be performed.

Other features and advantages of the present invention will become apparent from the following description of embodiments of the present invention with reference to the drawings.

[0010]

FIG. 1 is a schematic functional block diagram of one embodiment of a radar-type underground exploration apparatus according to the present invention. The main components of the radar-type underground exploration device 1 radiate a pulse-like radio wave in the microwave region toward the ground surface 2 at a predetermined repetition frequency, and use a reflecting object 3 such as a buried object existing in the ground. A transmitting / receiving unit 10 for receiving the reflected wave that has been reflected back, an amplifying unit 20 for amplifying the received reflected wave, a sampling unit 30 for sampling the sequentially received and amplified reflected wave while shifting the sampling point, And a signal evaluation unit 40 that combines the sampled signals to restore the reflected wave, and evaluates and displays the restored reflected wave. Here, the amplifying unit 20, the sampling unit 30, and the signal evaluation unit 40 are combined to form a reception signal processing unit 200
Call. Further, between the transmission / reception unit 10 and the amplifying unit 20, there is provided a blocking unit 50 for controlling the flow of a signal therebetween.

The transmission / reception unit 10 includes a transmission trigger generator 11 for generating a transmission trigger pulse in accordance with a set repetition frequency, and a first pulse generator 12 for generating a pulsed radio wave in response to the transmission trigger pulse. A transmission / reception unit 13 that receives the pulse wave generated by the first pulse generator 12 and radiates it into the ground, and receives the reflected wave reflected back from the underground reflective object 3 and Is provided. This transmitting / receiving unit 1
3, the directional coupler 13a includes a directional coupler 13a, a balun 13b, and a transmission / reception antenna 13c from the first pulse generator 12 side in the stated order. The pulse wave input terminal is a pulse generator 12
In addition, the reflected wave output terminal is connected to the amplification unit 20 via the cutoff means 50 which is a subsequent circuit.

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

The sampling section 30 includes a sampler driving section 31 for determining a sampling timing in response to a transmission trigger pulse, and a sampler 32 for sampling a reflected wave amplified by a command from the sampler driving section 31 at a predetermined time point. It has. The sampling unit 30 samples each reflected wave sent from the amplifying unit 20 in the repetition cycle using a sampling gate whose sampling point is sequentially shifted on the time axis. That is, sampling is performed at one sampling point from the reflected wave received by the first transmitted wave, and is sampled at a sampling point slightly delayed from the reflected wave received by the next transmitted wave. By performing this operation twice, sampling of the entire reflected wave in a desired time region is completed. That is, a sampling signal of one entire reflected wave is obtained from the 1000 reflected waves sequentially received.

The signal evaluation section 40 includes a signal processing section 41 for restoring a reflected wave from the signal sampled by the sampling section 30 to evaluate the underground exploration and a display section 42 for displaying the restored reflected wave. I have.

The cut-off means 50 includes the transmitting / receiving unit 13 and the amplifying unit 2
A high-frequency switch 51 interposed in a signal line between 0 and 0;
A second control pulse having a desired pulse width for the high-frequency switch 51 is generated in synchronization with the transmission trigger pulse.
A pulse generator 52, a waveform shaper 53 for shaping a pulse wave generated by the second pulse generator 52, and a time axis for delaying the generated control pulse on the time axis to cut the reflected wave And a delay circuit 54 for determining the position of Here, the delay circuit 54 is configured such that the delay time can be changed and set as appropriate by setting the volume of the delay time. The shut-off means 50 includes the pulse generator 12,
In the predetermined time range (about 15 ns) from the point in time when the pulse wave is generated in 52, the signal is blocked from entering the reception signal processing unit 200. Basically, the reception signal processing unit 200 It blocks the transmission / reception unit reflection signal which is a reflection signal from the transmission / reception unit 13 itself due to the pulse wave. Therefore, at least from the time when the pulse wave is generated in the pulse generators 12 and 52, the antenna reflection signal, which is the reflection signal from the antenna 13 c provided in the transmission / reception unit 13 due to the pulse wave, reaches the high-frequency switch 51. In the time domain up to the point in time, the shutoff is performed. If necessary, the cutoff time range can be extended to a time for covering the ground surface reflected wave by volume adjustment.

The operation of the radar type underground exploration apparatus 1 having the above-described configuration will be described with reference to the time chart of FIG. As shown in FIG. 2A, the transmission trigger generator 11 generates 1 μs
A transmission trigger pulse is generated at a period of. Accordingly, in response to the transmission trigger pulse, the first pulse generator 1
2 to 2 (b), a pulse wave is generated and radiated from the transmitting / receiving antenna 13c into the ground via the directional coupler 13a. The repetition frequency of the transmission radio wave radiated from the transmission / reception antenna 13c is 1 Mz. The propagation speed of radio waves in the ground depends on the geology, for example, 10 cm / ns
Then, the time required for the reflected wave from the depth of 5 m to return is 100 ns. Normally, the exploration area such as gas pipeline is underground 5
m, a repetition frequency of 1 Mz is sufficient. The reflected wave from the ground of the wave transmitted in this way is also received by the transmission / reception antenna 13c and transmitted to the lower side via the directional coupler 13a. In this state,
At all times, the output from the directional coupler 13a is continuously output. The output includes a linear reflection signal from the directional coupler 13a generated by the pulse wave, a balun 13b.
, And a direct reflection signal from the antenna 13c. FIG. 2 shows such a signal.
(C). As shown in the figure, the signal includes an initial signal A having a relatively large amplitude and a signal B arriving relatively late and having a relatively small amplitude. The signal A is composed of a direct reflected wave from the device constituting the transmitting and receiving unit 13 and a reflected wave on the ground surface. On the other hand, the signal section B is a signal from the underground, for example, from a gas pipe.

In the interruption of the interruption section, the control pulse generated by the second pulse generator 52 in response to the transmission trigger pulse is shaped by the waveform shaper 53, and the delay circuit 54 sets a predetermined time from the rise of the transmission trigger pulse. The signal is sent to the high-frequency switch 51 with a time delay. And
An interruption operation of a signal between the transmission / reception unit 13 and the reception signal processing unit 200 in a predetermined interruption time range is performed.
That is, a high-frequency switch drive trigger is formed as shown in FIG. 2D, and is sent to the high-frequency switch 51 to open and close the high-frequency switch 51 in a state as shown in FIG. Accordingly, the reception signal processing unit 200 outputs the relatively initial signal of the output from the transmission / reception unit 13 in the state shown in FIG. Only signals in the state shown in (f) are sent.

The STC signal shown in FIG. 2G provided in the reception signal processing unit 200 is a signal that increases stepwise with the count of the transmission trigger pulse. In this embodiment, the number of transmission trigger pulses is counted 1000 times. At the lowest level back. Since the amplification factor of the amplifier 22 changes in accordance with the signal level of the STC signal,
Repeats from the lowest level amplification rate to the highest level amplification rate in a cycle of 1 ms. At this stage,
In the signal portion shown in FIG. 2 (c), since the signal is removed from the portion where the amplitude is large, the signal does not saturate even if amplification is performed up to the highest level of amplification factor. Therefore, even when a configuration including a transmission / reception integrated transmission / reception unit is employed as in the present application, a desired signal is satisfactorily extracted, and information having a large attenuation in the ground is appropriately amplified to obtain a useful ground. Inside information can be obtained.

Sampling is performed by one sampling gate for one reflected wave reception signal received at a repetition period of 1 μs. The time position of the first sampling gate is set at the position on the time axis corresponding to the ground surface 2, and thereafter sampling is performed at a point delayed by 0.1 ns every repetition cycle of the transmission radio wave. That is, the n-th sampling is 1 μm from the (n−1) -th sampling.
Performed after s + 0.1ns. This sampling is 1000
Return to the first sampling point again each time. This means that a time region of 100 ns was sampled by sampling 1000 times, which corresponds to a region having a depth of 5 m from the ground surface 2 and is a sufficient region for exploring a gas conduit or the like. If the sampling interval is 0.1 ns, the micro can satisfactorily restore the waveform of the reflected wave in the region. By operating in this manner, 100
The restored reflected wave can be formed by synthesizing the signals sampled one by one from the 0 reflected waves. The display cycle of the reflected wave is 1 μs * 1000 = 1 ms, and the time axis is 1
It is stretched 000 times. By doing so, the image can be displayed on the display unit 42 having a low resolution. In this configuration,
Both the reflected wave from the reflector near the ground surface 2 and the reflected wave from the reflector away from the ground surface 2 depended on the time by the STC signal despite the large attenuation rate of the radio wave in the ground. By changing the amplification factor, it is displayed at almost the same level, facilitating exploration evaluation.

The present invention is not limited to the values such as the repetition frequency and the sampling interval used in the above description, and it goes without saying that the present invention can be implemented with various values as needed. In the above-described embodiment, the configuration is such that the initial signal is always cut off regardless of the amplification factor in the amplification unit 50. However, when the amplification factor in the amplification unit 50 is a certain level or more, Only the configuration may be such that the blocking means of the present application works. In this case,
The configuration may be such that a signal is received from the amplifying section 50 and the signal input from the delay circuit 54 to the high-frequency switch 51 is permitted only when the gain signal is higher than a predetermined value. With this configuration, the load on the high-frequency switch 51 can be reduced.

[Brief description of the drawings]

FIG. 1 is a functional block diagram showing an example of a radar type underground exploration device according to the present invention.

FIG. 2 is a time chart showing the operation of the radar type underground survey device shown in FIG. 1;

FIG. 3 is a diagram illustrating a comparison between an output (a) when a transmitting / receiving integrated transmitting / receiving section is provided and an output (b) when a separate transmitting / receiving type transmitting / receiving section is provided.

[Explanation of symbols]

 Reference Signs List 13 transmitting / receiving section 13c transmitting / receiving antenna 20 amplifying section 50 blocking means 51 high-frequency switch

Claims (5)

[Claims] A pulse generator for generating a pulse wave at a predetermined repetition period; receiving a pulse wave from the pulse generator and radiating the pulse wave into the ground; and receiving a reflected wave returned from the ground. Equipped with an integrated transmission and reception unit,
A radar-type underground exploration device that sends the reflected wave received by the transmission / reception unit to a reception signal processing unit and obtains a useful underground information signal with an amplification process in the reception signal processing unit, wherein the reception signal A radar type underground exploration apparatus, wherein the processing unit is provided with a blocking unit that blocks a transmission / reception unit reflection signal which is a reflection signal from the transmission / reception unit itself due to the pulse wave. 2. A pulse generator for generating a pulse wave at a predetermined repetition period, receiving a pulse wave from the pulse generator and radiating the pulse wave into the ground, and receiving a reflected wave returned from the ground. Equipped with an integrated transmission and reception unit,
A radar-type underground exploration device that sends the reflected wave received by the transmission / reception unit to a reception signal processing unit and obtains a useful underground information signal with amplification processing in the reception signal processing unit, And a high-frequency switch between the reception signal processing unit and the reception signal processing unit in a cutoff time range in which a predetermined time has elapsed from a point in time when the pulse wave is generated in the pulse generator by the high-frequency switch. A radar type underground exploration device equipped with a blocking means for blocking a signal from entering. 3. The cutoff time range in which the cutoff operation is performed by the cutoff means starts from the point in time when the pulse wave is generated in the pulse generator, and starts from the antenna itself provided in the transmitting and receiving unit due to the pulse wave. 3. The radar type underground exploration apparatus according to claim 2, wherein the antenna reflection signal, which is a reflection signal of the radar, is in a time range up to a time point when the antenna reflection signal reaches the high-frequency switch. 4. The shut-off time range in which the shut-off operation is performed by the shut-off means is configured such that the time at which the pulse wave is generated in the pulse generator is set as a cut-off start time and the cut-off end time is variable. Item 3. A radar type underground exploration device according to item 2. 5. The radar type underground exploration apparatus according to claim 1, wherein the cutoff operation by the cutoff means is performed only when an amplification factor of the amplifier is larger than a predetermined value.