JPH058992B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a buried object exploration device using pulsed radio waves, and is particularly useful for improving the depth of exploration and reducing the unexplorable area near the ground surface. The present invention relates to a suitable buried object exploration device.

[Prior art]

As a buried object detection device using pulsed radio waves, conventional
The device described in No. 6 is known. This device uses a simple signal processing circuit to remove noise and clutter signals, making it possible to detect underground steel pipes up to a depth of about 3 meters. With this type of device, the challenge is to improve the limit of the depth that can be probed because radio waves attenuate as they propagate underground.
In order to solve this problem, the above proposal uses a technique called sensitive time control (STC) or time-varying gain control (TVG). These methods increase the gain of the amplifier as the observation depth increases, that is, the time from pulsed radio wave emission to detection of reflected waves increases.

[Problem that the invention seeks to solve]

However, according to the above method, although it is possible to increase the intensity of the reflected wave, there is a problem in that the signal-to-noise ratio cannot be improved because noise components such as those from the amplifier are also amplified. One possible solution to this problem is to lower the frequency used when observing deep areas. This is because, as described in the April 10, 1974 issue of the Journal of Geophysical Research, pages 1699 to 1708, the higher the frequency, the greater the attenuation associated with radio wave propagation in the soil. by. However, with pulse radar, the reflected waves from the ground surface are generally first detected with high intensity, so if radio waves with a low frequency, that is, a large pulse width, are used, the time for these surface reflected waves to be detected increases, and the waves are detected near the ground surface. There was a problem that even if there was a target reflection, it could not be identified. As a result, if the depth of the exploration target was unknown, there was a serious drawback that targets near the surface could be missed.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a buried object exploration device that can reduce the unexplorable area near the earth's surface and increase the exploration depth.

[Means for solving problems]

In order to achieve the above object, the present invention provides an oscillator that oscillates a pulsed radio wave in a pattern consisting of a plurality of pulses with sequentially different pulse widths and pulse amplitudes, and a ground source that transmits the radio waves oscillated from this oscillator. a transmitting antenna that emits toward the buried object;
a receiving antenna that receives reflected waves from the underground object; an amplifier that amplifies the received radio waves; and a sampler that samples the amplified radio waves at multiple points in correspondence with the plurality of pulses;
In a buried object exploration device that includes a video processing device that converts the sampled radio waves into a video signal, and a display device that displays an image of a cross section of the earth using the video signal, the video processing device A determination means is provided for determining whether or not a buried object can be confirmed, and a plurality of patterns each having a different pulse width and pulse amplitude of the pulsed radio waves are stored in advance, and one selected pattern is provided. Accordingly, the pulse width and pulse amplitude of each pulse of the oscillator are controlled, and based on the determination result output from the determination means corresponding to this pattern, if a buried object cannot be confirmed, the pattern is changed to a pattern with a larger pulse width. However, if a buried object is confirmed, change to a pattern with a smaller pulse width,
The present invention is characterized in that a control signal generator is provided that repeatedly controls the pulse width and pulse amplitude of each pulse of the oscillator.

[Effect]

According to the above configuration, when observing deep areas, radio waves with wide pulse widths and high amplitudes are emitted to prevent the attenuation of the reflected intensity from areas with long propagation distances and are visualized efficiently, while for shallow areas, radio waves with narrow pulse widths are emitted. By emitting radio waves with a small amplitude, the time period during which weak target reflected waves are hidden by ground reflected waves can be reduced, thereby reducing the area where the target cannot be detected.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a buried object exploration device according to the present invention will be described below with reference to the drawings.

FIG. 1 shows the basic configuration of this embodiment. 1 is a wideband antenna for transmission, and 2 is a wideband antenna for reception. These wideband antennas 1 and 2 are
A known antenna such as a resistor-loaded dipole antenna is used, and it is mounted on a trolley 3 and is movable. Pulsed radio waves are emitted from a transmitting antenna 1, and reflected waves from an exploration target 4 are received by a receiving antenna 2. A pulse signal from an oscillator 5 is applied to the transmitting antenna 1, and the oscillator 5 is oscillated by a control signal generator 6 to control the amplitude and frequency of the pulse signal. A signal received by the receiving antenna 2 is amplified by an amplifier 7 and further sampled by a sampler 8. This sampled signal is led to the video processing device 9, where this signal is visualized and displayed on the display device 1.
Displayed as 0. Further, the position of the cart 3, that is, the positions of the antennas 1 and 2 is also input to the video processing device 9. This position detection is performed by the position detection device 11.

Next, each part will be explained in detail with reference to the signal waveforms of each part shown in FIG. In this example, sampler 8
A case will be explained in which eight sample points are provided to form one waveform, but normally 100 or more sample points are provided. The oscillator 5 not only oscillates a pulse output, but also oscillates a trigger pulse that time-divisions a signal synchronized with the pulse output. And the pulse output is the transmitting antenna 1
Then, the trigger pulse is guided to the sampler 8 and the control signal generators 6,8. Signal sampling is repeated in synchronization with trigger pulses 1 to 8, and one waveform is formed by eight points of sampling data.
As shown in FIG. 2, the amplitude and pulse width of the pulses emitted from the oscillator 5 are controlled by the control signal generator 6, and the amplitude and pulse width become larger as the sampling position moves to the position where the trigger pulse number is larger. It's starting to happen. Here, the smaller the trigger pulse number, the shallower the depth to be observed.
That is, the time interval between the sample gate in the sampler 8 and the trigger pulse of the oscillator 5 increases as the number of the trigger pulse increases. Furthermore, the shallower the observation depth, that is, the smaller the sampling number, the shorter the pulse width and the smaller the wave height.
As the observation depth becomes deeper, the pulse width becomes wider and shifts to the lower frequency side, and the pulse output also becomes larger. Such a pulse signal is radiated from the transmitting antenna 1, and the signal reflected by the target object is received by the receiving antenna 2 and amplified by the amplifier 7.
This is the output waveform of the amplifier 7 shown in the figure. The output of the amplifier 7 first has a ground reflection r similar to the output of the oscillator 5.
is detected, and then the reflected wave R of the target object 4 is detected with a time delay. Inside the sampler 8, a sampling gate is provided at a position delayed by a fixed time from the trigger pulse oscillated by the oscillator 5, and the output value of the amplifier 7 is sampled and held at this sampling gate until the next timing. These sampling means are well known in conventional sampling oscilloscopes and the like. Oscillator 5
The time delay from the trigger pulse to the gate of the sampler 8 is linked to the control signal of the control signal generator 6, and in the example of FIG. 2, the time delay is minimum when the sampling number is 1 and maximum when the sampling number is 8. The waveform obtained by sampling and holding the output of the amplifier 7 at each sampling gate, that is, the output of the sampler 8, is a waveform obtained by temporally extending the output waveform of the amplifier 7. This waveform becomes a waveform whose frequency shifts to a lower frequency as the sampling number increases. This waveform is subjected to image processing by the image processing device 9. The waveforms of each part have been explained above.

Next, the specific contents of the oscillator 5 will be explained with reference to FIG. FIG. 4 is a diagram showing waveforms of each part of the oscillator 5. 501 is an oscillator, and this oscillator 501
The waveform oscillated by has a sharp rise and a gradual attenuation. Reference numeral 502 denotes a bandpass filter, which is a well-known filter whose frequency band is controlled by the output value of a control signal generator 6, which will be described later. In a bandpass filter, the signal first passes through a reduction filter and then a high-pass filter. When the signal passes through the reduction filter, as shown in FIG. 4, the rise time of the sharp rise portion becomes longer. Furthermore, the waveform whose tip portion is differentiated by a high-pass filter is output from the band-pass filter 502. When the band of the band pass filter 502 is controlled to move toward lower frequencies, the output waveform of the band pass filter 502 becomes a waveform with a large pulse width and many low frequency components, as shown by the broken line in FIG. Reference numeral 503 denotes a voltage-controlled attenuator, the amount of attenuation of which is controlled by the output value of a control signal generator 6, which will be described later.

Next, control of the output value of the control signal generator 6, that is, the frequency component and pulse amplitude of the pulse 2, will be explained. As shown in FIG. 2, the deeper the area is observed, the lower the frequency is shifted, and the amplitude is increased as necessary. This control is performed by the output waveform of the control signal generator 6. That is, the control signal generator 6 receives signals from the sampler 8 synchronized with the sample numbers 1 to 8 numbered in FIG. 2, and outputs a preset functional control voltage. For example, the signal synchronized with sample number 1 in FIG. 2 is a signal meaning that one waveform has been sampled in the sampler 8, and the function generator starts outputting based on this signal, and this operation is repeated.

As a result, basically, the deeper the observation area is, the lower the frequency used can be shifted to, and the amplitude of the pulse used can be increased as necessary. In this case, since the depth of the target is constant, the time from transmission to reception is constant, and the level of the received wave increases as the observation area gets deeper. This can be achieved by increasing the height of the transmitted wave and shifting the frequency to lower frequencies to reduce attenuation during propagation. As a result, even if the target is deep and the radio wave propagation distance is long, it is possible to reduce signal attenuation due to propagation, and it is possible to obtain target reflected waves that reach deep parts, making it possible to visualize them. It becomes possible.

Next, features of this embodiment will be explained with reference to FIGS. 5 and 6. The feature of this embodiment is that the oscillator 5 is controlled by the output of the video processing device 9 via the control signal generating device 6. In this embodiment, a plurality of control patterns are prepared in advance to be input into the memory, and one of them is selected to scan the antennas 1 and 2 to visualize the buried object. Based on this visualized result, other patterns are selected to further improve the image quality. That is, if a buried object cannot be confirmed as a result of visualization, the used pattern is shifted to a control pattern with a lower frequency pulse waveform and a larger pulse amplitude. Conversely, when an image of the target object is obtained, the control pattern is shifted to a higher frequency side in order to improve the accuracy of this image. FIG. 5 shows the configuration of the control signal generator 6 that performs such control. 610 is a microcomputer, 611,6
12 are storage elements, and 613 and 614 are digital-to-analog conversion elements. A plurality of control patterns are stored in advance in the memory elements 612, 612. Based on the image processing results from the video processing device 9, the microcomputer 6
10 selects one of the control patterns and stores storage data for this pattern in the storage element 611,
Digital-to-analog conversion element 6 sequentially from 612
Send to 13,614. These converted analog signals are passed through a bandpass filter 50 as a control signal.
2, sent to attenuator 503.

For example, the operation of the microcomputer 610 in the case of 8 samples for one waveform shown in FIG. 2 will be explained with reference to the flowchart shown in FIG. In step 701, a preset pattern is first selected and data is collected. Next, in step 702, the signal from the sampler 8 is received to determine the initial position of the sample.
That is, it waits until sample number 1 is detected.
Next, in step 703, sample number 1 is detected and the start address of the selected pattern is set.
Next, in step 704, a trigger pulse from the oscillator 501 is detected, and in step 705, the address is updated each time a trigger pulse is detected. When the final address, that is, sample number 8 is reached, this is confirmed in step 706, and it is determined in step 707 whether or not scanning has ended. If not completed, the process returns to the pattern start address and repeats the above operation. If it is determined in step 707 that scanning has ended, the image has been obtained, and in step 708 the input of the determination result as to whether or not to change the pattern and visualize it again is obtained, and in step 709 this input is determined to be completed. A determination is made as to whether or not. And if not finished, step
710 to update the pattern and repeat the steps from data collection to visualization.

According to this embodiment, since the control pattern is repeatedly changed so that the target object can be observed with high accuracy, it is possible to obtain a target image with the best image quality by repeating antenna scanning.

In each of the above-mentioned embodiments, a case has been described in which a combination of a step-shaped oscillator and a bandpass filter is used to change the frequency component of the pulse, but it is also possible to control the frequency component within the pulse using an external electrical control signal. It's okay. In this case, the oscillation efficiency of the oscillator improves, it becomes possible to widen the range of change in pulse amplitude, and it is also possible to increase the limit distance of the exploration depth.

〔Effect of the invention〕

As described above, according to the present invention, the pulse width, that is, the frequency and pulse amplitude, of the emitted radio waves is changed depending on the observation depth, and the pulse width can be shortened when observing near the ground surface. The undetectable area due to reflection can be reduced. Furthermore, since the amount of attenuation of reflected waves from deep exploration targets can be reduced, a clear target image can be obtained, and furthermore, the limit of exploration depth can be significantly improved. In addition to the above basic effects, according to the present invention, a plurality of patterns with different pulse widths and amplitudes are prepared in advance, and the patterns are changed based on the results of exploration. The detection accuracy and detection sensitivity are automatically improved according to the depth of the object, which has the effect of greatly expanding the detection range and improving the range of detection targets.

Further, there is an effect that the exploration work can be extremely simplified.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing an embodiment of a buried object exploration device according to the present invention, FIG. 2 is a diagram showing waveforms of each part shown in FIG. 1, and FIGS. 3 and 4 are main points of FIG. 1. FIG. 5 is a block diagram of the control signal generator of the characteristic part of the embodiment of FIG. 1, and FIG. 6 is a flowchart showing its operation. DESCRIPTION OF SYMBOLS 1... Transmission antenna, 2... Receiving antenna, 4... Exploration target, 5... Oscillator, 6... Control signal generator, 7... Amplifier, 8... Sampler,
9... Video processing device, 10... Display device.

Claims (1)

[Claims] 1. An oscillator that oscillates a pulsed radio wave in a pattern consisting of a plurality of pulses with sequentially different pulse widths and pulse amplitudes, and a transmitting antenna that radiates the radio waves oscillated from this oscillator toward underground objects. , a receiving antenna that receives reflected waves from the underground object, an amplifier that amplifies the received radio waves, and a sampler that samples the amplified radio waves at multiple points in correspondence with the plurality of pulses. , a buried object exploration device equipped with a video processing device that converts the sampled radio waves into a video signal, and a display device that displays an image of a cross section of the earth using the video signal; A determination means is provided for determining whether a buried object can be confirmed or not, and a plurality of patterns having different pulse widths and pulse amplitudes of each pulse of the pulsed radio waves are stored in advance, and a selected one is The pulse width and pulse amplitude of each pulse of the oscillator are controlled according to the pattern, and based on the determination result output from the determination means corresponding to this pattern, if a buried object cannot be confirmed, a pattern with a larger pulse width is used. A buried object characterized in that it is provided with a control signal generator that repeatedly controls the pulse width and pulse amplitude of each pulse of the oscillator by changing the pattern to a pattern with a smaller pulse width when a buried object is confirmed. Exploration equipment.