JPH11183635A - Apparatus and method for detecting hidden object in ground - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a detecting apparatus that can highly accurately detect a position where a hidden object is buried in the ground. SOLUTION: An apparatus includes a transmitter 52 generating transmission signals of a predetermined frequency, a transmission pulse generator 54 generating transmission pulse signals in relation to the transmission signals, a transmission antenna 56 for transmitting electromagnetic waves based on the transmission pulse signals, a reception antenna 58 for receiving reflecting waves from an underground hidden object, a phase shift means 64 for varying and delaying a phase of the transmission signals as required, a sampling pulse generator 72 generating sampling pulse signals in relation to the delayed transmission signals, a sampling means 62 for sampling signals received at the reception antenna 58 on the basis of the sampling pulse signal, and a signal-processing means 74 for integrating received signals sampled by the sampling means 62, thereby detecting a position of the underground hidden object.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an underground concealed object detecting apparatus and method for detecting a concealed object already existing in the ground using electromagnetic waves.

[0002]

2. Description of the Related Art Underground concealed object detecting devices for detecting concealed objects existing in the ground are known. Known detection devices include a transmitter that generates a transmission signal, a transmission antenna that transmits an electromagnetic wave toward an underground concealment object based on a signal from the transmitter, and a reception that receives a reflected wave from the underground concealment object. An antenna, sampling means for sampling a received signal received by the receiving antenna, and signal processing means for processing the sampled signal are provided.

[0003]

In the detection apparatus of the sampler system described above, the peak value of the pulse of the transmission signal is usually 3 or more.
Since about 0 to 100 V is required, the repetition frequency of the pulse of the transmission signal is as slow as about 50 to 500 kHz, for example.
This makes it difficult to detect the position of the underground concealment object with high accuracy.

[0004] In order to solve such a problem, the present applicant proposed in Japanese Patent Application No. 9-65066 an obstacle detection device in the underground propulsion method. As shown in FIG. 5, the proposed detection device includes a variable period oscillator 2, a fixed delay circuit 4, a transmitter 6, and a transmission antenna 8. The variable period transmitter 2 is a voltage controlled transmission circuit (abbreviated as V
CO), and generates a pulse signal having a variable period that is sequentially extended by a small amount of time Δt each time in the first period, and sends the variable period pulse signal to the fixed delay circuit 4 as a variable period signal. This variable period signal is also sent to a correlation signal generator described later. The fixed delay circuit 4 generates a fixed delay signal obtained by delaying the variable period signal by a predetermined fixed delay amount, and sends the fixed delay signal to the transmitter 6. The transmitter 6 generates a transmission signal based on the fixed delay signal, and sends the transmission signal to the transmission antenna 8. The transmission antenna 8 generates an electromagnetic wave based on a transmission signal, and transmits the electromagnetic wave toward an obstacle existing in the ground, for example, a gas pipe.

[0005] The detection device also includes a receiving antenna 10, a high-frequency amplifier 12, a correlation signal generator 14, and a signal processing means 16. The reception antenna 10 receives the electromagnetic wave reflected from the obstacle after being transmitted from the transmission antenna 8, and sends a reception signal to the high-frequency amplifier 12. The high-frequency amplifier 12 amplifies the received signal. The correlation signal generator 14 generates, as a correlation signal, a signal having a promised waveform of a monocycle waveform having a predetermined time length for each variable period signal from the variable period generator 2, and sends the correlation signal to the signal processing means 16. I do. The signal processing means 16 includes a multiplication circuit, an integration circuit, and an amplification circuit. The multiplication circuit generates a multiplication signal by multiplying each amplitude width of the reception signal from the high-frequency amplifier 40 and the correlation signal from the correlation signal generator 14, and the integration circuit integrates the multiplication signal from the multiplication circuit. And an amplifier circuit amplifies the integrated signal to generate an amplified signal. The signal processing means 16 further includes:
A correlation detection process and a pulse compression process are performed on the amplified signal to generate a detection signal. The detection signal includes information on the embedment position of the obstacle, and the embedment position of the obstacle can be displayed on the display unit 18 by using the detection signal.

In this detection device, the fixed delay signal supplied to the transmitter 6 becomes a promised waveform, that is, a monocycle signal, which is delayed by a fixed delay amount from the time of the variable period signal for each variable period. Further, the correlation signal given to the signal processing means 16 is a promised waveform for each variable period, that is, a monocycle waveform. Therefore, the transmitter 6 transmits the transmission signal of the promised waveform delayed by the fixed delay amount while sequentially extending the detection period Δt for each variable period.
, The received signal received by the receiving antenna 10 is a received signal delayed by Δt for each period, like the transmitted signal, and this received signal is
3 is always a signal delayed by a fixed delay amount. Therefore, when viewed from the correlation signal sent to the signal processing means 16, the received signal received by the receiving antenna 10 is
Correlation signals after the second time in the variable period are delayed first, and this received signal is received at a time sequentially raised by Δt in each variable period. As described above, the variable period signal from the variable period generator 2 is generated on the one hand by the fixed delay circuit 4 to generate the fixed delay signal, and on the other hand the correlation signal generator 14 generates the correlation signal, as described above. Then, the position of the buried obstacle can be detected.

However, even in the proposed obstacle detecting device, the generation of the variable period signal which is sequentially extended by the small amount of time Δt is performed by the VCO control by the voltage control transmission circuit, so that the circuit configuration becomes complicated. VCO
For example, a digital multivibrator is used to generate a variable period signal by control.When this digital multivibrator is used, characteristics in a frequency band used to detect an underground obscured object change due to a temperature change, and an obstacle It is difficult to detect the embedded position with high accuracy.

An object of the present invention is to provide an apparatus and a method for detecting an underground concealed object capable of detecting the buried position of the underground concealed object with high accuracy.

It is another object of the present invention to provide an apparatus and method for detecting a concealed object which is relatively small and can be mounted in a small-diameter propulsion pipe.

[0010]

According to the present invention, there is provided a transmitter for generating a transmission signal having a predetermined frequency, and a transmission pulse for generating a transmission pulse signal in relation to the transmission signal from the transmitter. A generator, a transmission antenna for transmitting an electromagnetic wave based on the transmission pulse signal from the transmission pulse generator toward an underground concealment, and a reception antenna for receiving a reflected wave from the underground concealment Phase shifting means for varying and delaying the phase of the transmission signal from the transmitter as required, and sampling pulse generation for generating a sampling pulse in relation to the transmission signal delayed by the phase shifting means A sampling unit that samples the received signal received by the receiving unit based on a sampling pulse generated by the sampling pulse generator. Means and a detection device in the ground concealing matter, characterized by comprising signal processing means for detecting the position of the underground concealer the received signal sampled by processing the low frequency by the sampling means.

According to the present invention, the transmitter generates a transmission signal of a predetermined frequency, the transmission pulse generator generates a transmission pulse signal based on the transmission signal, and the transmission antenna transmits an electromagnetic wave based on the transmission pulse signal. I do. Therefore, the transmission signal from the transmission antenna and the reception signal received by the reception antenna are signals corresponding to the period of the predetermined frequency of the transmission signal. Further, the phase shift means makes the phase of the transmission signal from the transmission means variable and delays, the sampling pulse generator generates a sampling pulse based on the delayed transmission signal, and the sampling means generates a sampling pulse based on the sampling pulse. To sample the received signal from the receiving antenna. Since the phase shifting means delays the phase of the transmitted signal, the sampling signal generated by the sampling pulse generator is delayed by a predetermined time. By generating such a sampling pulse, the signal received from the receiving antenna can be sampled as required, and the position of the underground concealment object can be detected. In such a detection device, for example, a crystal oscillator can be used as the oscillator, and a varicap can be used as the phase shift means. With such a configuration, the peak value of the transmission pulse can be reduced to about 3 V. The size of the circuit configuration of the detection device can be reduced.

According to a second aspect of the present invention, the frequency of the transmission signal generated by the transmitter is transmitted at 1 MHz or more, and the received signal sampled by the sampling means is integrated. .

According to the present invention, since the frequency of the signal transmitted by the transmitter is 1 MHz or more, the period of the transmission signal generated by the transmitter and the period of the sampling pulse generated by the sampling pulse generator are very short. In this connection, sampling can be performed many times in a short period of time, whereby the position of the underground concealed object can be detected at high speed and with high accuracy.

According to a third aspect of the present invention, the amount of delay of the transmitted signal by the phase shifter is 1 to 1000 ns, which is a range covering one cycle of the transmitted signal.

According to the present invention, since the amount of delay of the transmitted signal by the phase shift means is in a range covering one cycle of the transmitted signal by the transmitter, the amount of delay of the received signal of the receiving antenna over the period of one cycle of the transmitted signal. Is sampled, whereby the position of the underground concealed object can be detected with high accuracy.

Further, according to the present invention, a transmission signal of a predetermined frequency is generated by a transmitter, a transmission pulse signal is generated by a transmission pulse generator in relation to the transmission signal, and the transmission pulse signal is generated based on the transmission pulse signal. The electromagnetic wave is transmitted from the transmitting antenna toward the underground concealed object, and the reflected wave from the underground concealed object is received by the receiving antenna, and the phase of the transmitted signal is delayed by a phase shift means as required, and A sampling pulse is generated by a sampling pulse generator in association with the delayed transmission signal, the reception signal is sampled by sampling means based on the sampling signal, and then the sampled reception signal is integrated by signal processing means. And detecting the position of the underground concealed object.

According to the present invention, since it has the same configuration as the first aspect of the invention, the same operation as described above is achieved.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an apparatus and method for detecting an underground concealed object according to the present invention will be described below. FIG. 1 is a block diagram schematically showing an embodiment of a detection device for implementing a detection method according to the present invention, and FIG. 2 is generated in the detection device of FIG. 5 is a time chart for explaining various signals.

Referring to FIG. 1 and FIG. 2, an underground concealed object detecting device shown in FIG.
And a transmission antenna 56. The transmitter 52
For example, it is composed of a crystal oscillator and generates a transmission signal P1 having a predetermined frequency. The transmission signal P1 from the oscillator 52
May be, for example, a sine wave (see FIG. 2). Oscillator 52
By using a crystal oscillator as the above, the frequency of the transmission signal can be stabilized without being affected by the temperature, and the peak voltage value of the high-frequency transmission signal can be easily obtained at, for example, about 3 V. In order to detect an underground concealed object (not shown), for example, a gas pipe buried in the ground at high speed and with high accuracy, the frequency of the transmission signal P1 is increased, that is, 1 MHz or more. Is desirably set to, for example, 20 MHz. The transmission signal P1 from the oscillator 52 is sent to the transmission pulse oscillator 54, and the transmission pulse oscillator 54 generates the transmission pulse signal P4 when the transmission signal P1 rises from the zero point and reaches the predetermined value V1 (see FIG. 2). . Therefore, the transmission pulse signal P4 generated by the transmission pulse generator 54 is generated with a time T1 delay from the zero point of the rise of the transmission signal. The transmission pulse signal is transmitted to the transmission antenna 56, and the transmission antenna 56 transmits an electromagnetic wave toward the underground concealed object based on the transmission pulse signal.

This detecting device also includes a receiving antenna 5
8, a high frequency amplifier 60 and a sampling means 62 are provided. The receiving antenna 58 receives the electromagnetic wave reflected by the rear underground concealment (not shown) transmitted from the transmitting antenna 56 and sends the received signal P5 to the high-frequency amplifier 58. The receiving antenna 58 is a propulsion pipe (not shown) for propelling in the soil together with the transmitting antenna 58.
Attached to the tip of Since the reception signal P5 of the reception antenna 58 is a reception signal of an electromagnetic wave reflected from an underground concealment object, the reception signal P5 is a signal delayed with respect to the transmission pulse signal (see FIG. 2).
Also, the longer the distance between the receiving antenna 58 and the underground concealment tube is, the longer it becomes. Transmit antenna 56 and receive antenna 58
Can be composed of, for example, a bow-tie antenna known per se. Note that the transmitting antenna 56 and the receiving antenna 58 may be configured as separate dedicated antennas, and may be configured so that one antenna has the functions of both the transmitting antenna and the receiving antenna by distinguishing the operation time. Can also. High frequency amplifier 6
Numeral 0 amplifies the received signal from the receiving antenna 58 at a high frequency and sends the amplified received signal to the sampling means 62.

The signal transmitted from the oscillator 52 is transmitted to the phase shifter 6.
4 The illustrated phase shift means 64 includes a phase shift circuit voltage control means 66 and a variable voltage phase shift circuit 68. A phase shift circuit voltage control means 66 composed of a phase shift circuit voltage control circuit changes the voltage supplied to the voltage variable phase shift circuit 68. Further, the variable voltage phase shift circuit 68 varies the phase of the transmission signal based on the control voltage from the phase shift circuit voltage control means 66. That is, the voltage variable phase shift circuit 68 increases the delay of the transmission signal (in other words, increases the delay time) as the control voltage from the phase shift circuit voltage control means 66 increases, for example, while increasing the phase shift circuit. As the control voltage from the voltage control means 66 decreases, for example, the delay of the transmission signal is reduced (in other words, the delay time is shortened). As such a voltage variable phase shift circuit 68, for example, 30 to 200 pF
A circuit in which about five varicaps are incorporated can be used.
By changing the transmission signal by ５5 V, the phase of the transmission signal P1 can be delayed, for example, by 0 to 60 × 10 ^-9 seconds (0 to 60 ns). The circuit using the above-described varicap has good temperature characteristics of the circuit, and its characteristics are stable even when the temperature changes, and the variation of the zero point of the phase shift signal output from the phase shift unit 64 is suppressed. Can be reduced.

The phase shifter 64 generates the phase shift signal P2 (see FIG. 2) as described above. The phase shift signal P2 is a signal delayed by a predetermined time T from the transmission signal P1, and the phase delay time between the transmission signal P1 and the transmission signal P1 is changed by changing the control voltage supplied to the voltage variable phase shift circuit 68. Controlled. The delay amount of the phase shift signal P2 is related to the transmission frequency of the transmission signal P1,
000 ns is desirably set in an appropriate range.

The phase shifting signal P2 from the phase shifting means 64 is sent to a pulse generating circuit 70, which pulsates the phase shifting signal P2. The pulsed phase-shifted signal is then sent to a sampling pulse generator 72, which in this embodiment, based on the sent phase-shifted signal, receives a phase shift from a phase shifting means 64 in this embodiment. When the output value of the signal P2 reaches a predetermined value V2, a sampling pulse signal P3 (FIG. 2) is generated. That is, as shown in FIG. 2, the sampling pulse generator 72 generates the sampling pulse signal P3 when the predetermined value V2 is reached from the zero point of the rising edge of the phase shift signal P2, and sends the sampling pulse signal P3 to the sampling means 62. I do. The sampling pulse signal P3 generated by the sampling pulse generator 72 is set very short.

The sampling pulse signal P3 from the sampling pulse generator 72 functions as a gate signal of the sampling means 62.
When the sampling pulse signal P3 from 2 is sent,
The reception signal received by the reception antenna 58 is received and sent to the signal processing unit 74.

In this embodiment, the frequency of the transmission signal P1 is set to, for example, 20 MHz, and its cycle is 50 ns.
It is. In such a case, for example, during the first measurement period set to 312.5 μs, the phase shifter 64 outputs the transmission signal P
The sampling pulse generator 72 generates a phase shift signal P delayed by a predetermined time T from 1 and the sampling pulse generator 72 generates 6250 sampling pulse signals P3 based on the phase shift signal P2. Therefore, in the first measurement period, the sampling means 62 measures the received signal of the receiving antenna 58 6250 times based on the sampling pulse signal P3,
The measured sampling signal P6 (FIG. 2) is sent to the signal processing means 74. The signal processing means 74 includes an integrating circuit 73 and a memory 75. The integrating circuit 73 integrates the sampling signal P6 in such a first measurement period, and the integrated value obtained by the integrating process is stored in the memory 75.
Is stored. By integrating the measurement values measured many times in this manner, noise components can be reduced and highly accurate measurement can be performed. After the end of the first measurement period, the phase shift circuit voltage control means 66 increases the voltage supplied to the voltage variable phase shift circuit 68, for example, to a certain extent.
4 is a time shift (T + Δ) from the transmission signal P1.
T) The phase is delayed. During the next 312.5 μs second measurement period following the first measurement period, the phase shifter 64
The sampling pulse generator 72 generates a phase-shifted signal P delayed in time (T + ΔT) from the transmission signal P1, and based on the phase-shifted signal P2, the sampling pulse generator 72 operates in the same manner as in the first measurement period.
It generates zero sampling pulse signals P3. In addition,
The time ΔT for sequentially delaying is set to, for example, 0.117 ns. Similarly, in the second measurement period, the sampling means 62 measures the received signal of the receiving antenna 58 6250 times based on the sampling pulse signal P3, and sends the measured sampling signal P6 (FIG. 2) to the signal processing means 74. Pay. Next, the signal processing means 74
The sampling signal P6 during the measurement period is integrated with the integration circuit 73.
And the integrated value obtained by the integration process is stored in the memory 7.
5 is stored.

In this embodiment, as shown in FIG. 2, one cycle of the measurement is set to 80 ms. Therefore, from the start of the measurement in the first measurement period, the measurement in each measurement period described above is performed until the time reaches 80 ms. In the meantime, the phase shifter 64 generates a phase shift signal that is sequentially delayed by ΔT from the transmission signal P1, the sampling signal P6 for each measurement period is integrated by the integration circuit 73, and each integrated value obtained by the integration is stored in the memory 75. Stored in Note that the period of one cycle of measurement and each measurement period can be appropriately set according to the frequency of the transmission signal P1 and the like.

The signal processing means 74 further integrates the integrated value for one cycle stored in the memory 75, lowers the frequency, and generates the detection signal P7 (FIG. 2). The detection signal thus obtained is sent to the display means 76 such as a liquid crystal display device, and the embedded position information included in the detection signal is displayed on the display means 76.
By observing the detection information displayed in, the embedment position of the concealed object can be easily known.

In such a detecting device, a crystal oscillator can be used as the oscillator 52, whereby the peak value of the oscillation signal of the oscillator 52 can be set to, for example, 3V. Further, since the generation of the sampling ring pulse signal is performed by delaying the phase of the transmission signal of a constant frequency by the phase shift means 64, the circuit configuration for that purpose can be simplified. Therefore, the circuit configuration of the detection device can be simply and miniaturized, and can be advantageously applied to a small-diameter propulsion pipe for laying a small-diameter conduit for transporting gas or the like.

In the above embodiment, the transmission antenna 56
Although one embodiment of the detecting device has been described by applying the antenna and the receiving antenna 58 to a propulsion pipe for propelling underground, the present invention is not limited to this. The above detection device can be similarly applied to an example in which the antenna 58 is provided, and an example in which the receiving antenna 56 is mounted on a propulsion pipe and the receiving antenna 58 is mounted on a taxiing vehicle.

Example and Comparative Example As an example, a simulation experiment as shown in FIG. 3 was conducted to confirm the effect of the detection device having the above-described configuration. FIG.
1 shows a circuit configuration in a simulation experiment of a system using the detection device having the configuration shown in FIG. 1. In this circuit configuration, the detection device a has the same configuration as the detection device shown in FIG. The first attenuator b was connected to the antenna Tx, and the distributor c was connected to the first attenuator b. The attenuation value of the first attenuator b is set to a constant value in consideration of the signal attenuation by the transmission antenna Tx, the transmission attenuation of the interface between the transmission antenna Tx and the soil, and the like. ) Was set to 40 dB in this simulation experiment. A second attenuator d was connected to the distributor c, and a cable e was connected to the second attenuator d. Distributor c
, A correction cable f was connected, and the correction cable f was connected to the receiving antenna Rx of the detection device a. The distributor c guides the signal from the first attenuator b to the correction cable f via the second attenuator d and the cable e, and also guides the signal from the first attenuator b directly to the correction cable f. A signal guided from the first attenuator b to the correction cable f through the second attenuator d and the cable e corresponds to a reflected wave reflected by the underground concealment object, and a signal guided directly from the first attenuator b to the correction cable f is , Corresponds to a direct wave directly received from the transmitting antenna TX to the receiving antenna Rx. The attenuation value of the second attenuator d was set in consideration of the attenuation of electromagnetic waves in soil. The length of the cable e was set to correspond to the time required for the electromagnetic waves to reach the concealed object in the ground. In the embodiment, the attenuation value of the second attenuator d and the length of the cable e are set as shown in Table 1 according to the burial distance in the ground.

[0031]

[Table 1]

As shown in Table 1, for example, under the condition I where the underground burial distance is 0.1 m, in the actual detection device, the electromagnetic wave transmitted from the transmitting antenna is reflected by the concealed object and then transmitted to the receiving antenna. 2.8 ns to be received
ec and the cable e corresponding to the arrival time of this electromagnetic wave
Was set to 0.3 m, and the attenuation of the second attenuator d was set to 5 dB based on the actually measured value as the attenuation of the electromagnetic wave corresponding to this buried distance in the soil.

The auxiliary cable f is used to correct the electromagnetic wave arrival time caused by the system using the detecting device a, and the amount of the arrival time correction is set as the length of the correction cable f. Length of cable f is 10
cm.

In the embodiment, using such a circuit configuration,
A transmitter signal of 20 MHz is generated by the transmitter of the detection device a, and a transmission pulse signal is generated based on the transmitted signal.
The S / N ratio of the reception signal transmitted from the transmission antenna Tx and then received by the reception antenna Rx based on the transmission pulse signal was obtained by a simulation experiment. The S / N ratio under each of the conditions I to IV shown in Table 1 is as shown in the column of Example in Table 2. For example, in the case of the condition I,
The S / N ratio was 31.8 dB.

[0035]

[Table 2]

The S / N ratio under each of the conditions I to IV of this simulation experiment is as follows:

[0037]

(Equation 1)

[0038]

As a comparative example, a simulation experiment as shown in FIG. 4 was performed. FIG. 4 shows a circuit configuration in a simulation experiment of a system using the detection device described in the specification and drawings of Japanese Patent Application No. 9-65066 previously proposed by the present applicant. a1 has the same configuration as that of the detection device disclosed in Japanese Patent Application No. 9-65066. In the circuit configuration of the system of the comparative example, the point that a first correction cable g1 having a length of 8 m is interposed between the first attenuator b1 and the distributor c1 as a correction amount, and between the distributor c1 and the detector a1 Except that the length of the interposed second correction cable f1 was set to 8 m, the circuit configuration was substantially the same as that of the above embodiment.

In the comparative example, the circuit configuration shown in FIG.
The transmitter of the detection device a1 generates a 50 kHz sawtooth transmission signal, generates a transmission pulse signal based on the transmission signal, transmits the transmission pulse signal from the transmission antenna Tx based on the transmission pulse signal, and then receives the transmission pulse signal on the reception antenna Rx. The S / N ratio of the received signal thus obtained was obtained by a simulation experiment. S / in each of the conditions I to IV shown in Table 1
The N ratio was as shown in the column of Comparative Example in Table 2. For example, under the condition I of Comparative Example, the S / N ratio was 22.5 dB.

From the simulation experiments of the above-described examples and comparative examples, as shown in Table 2, the conditions I to
The average value of the S / N ratio of IV is 25 dB, the average value of the S / N ratio of the conditions I to IV of the comparative example is 15.1 dB,
From these, when using the detection device according to the embodiment,
It was found that the S / N ratio was improved by 10 dB on average, and that the underground concealed object could be detected with high accuracy by greatly reducing the noise component.

[0042]

According to the first aspect of the present invention, the transmitter generates a transmission signal of a predetermined frequency, the transmission pulse generator generates a transmission pulse signal based on the transmission signal, and transmits the signal. The antenna emits an electromagnetic wave based on the transmission pulse signal. Therefore, the transmission signal from the transmission antenna and the reception signal received by the reception antenna are signals corresponding to the period of the predetermined frequency of the transmission signal. Further, the phase shift means makes the phase of the transmission signal from the transmission means variable and delays, the sampling pulse generator generates a sampling pulse based on the delayed transmission signal, and the sampling means generates a sampling pulse based on the sampling pulse. To sample the received signal from the receiving antenna. Since the phase shifting means delays the phase of the transmission signal, the sampling signals generated by the sampling pulse generator are sequentially delayed by a predetermined time. By generating such a sampling pulse, the signal received from the receiving antenna can be sampled as required, and the position of the underground concealment object can be detected. In such a detection device, for example, a crystal oscillator is used as an oscillator,
In addition, for example, a varicap can be used as the phase shifting means. With such a configuration, the peak value of the transmission pulse can be set to about 3 V, and the circuit configuration of the detection device can be reduced in size.

According to the detecting device of the second aspect of the present invention, since the frequency of the signal transmitted by the transmitter is 1 MHz or more, the signal generated by the transmitter and the signal generated by the sampling pulse generator are generated. The period of the sampling pulse is very short, and in connection with this, sampling can be performed many times within a short time, so that the position of the underground concealment object can be detected at high speed and with high accuracy.

According to the detecting device of the third aspect of the present invention, since the amount of delay of the transmitted signal by the phase shift means is in a range covering one cycle of the transmitted signal by the transmitter, the delay amount of one cycle of the transmitted signal. The reception signal of the reception antenna is sampled over a period, and thereby, the position of the underground concealment object can be detected with high accuracy.

Further, according to the detecting method of the fourth aspect of the present invention, the same effect as that of the detecting apparatus of the first aspect is achieved.

[Brief description of the drawings]

FIG. 1 is a block diagram schematically showing an embodiment of a device for detecting an underground concealed object according to the present invention.

FIG. 2 is a time chart showing various signals generated in the detection device of FIG.

FIG. 3 is a block diagram schematically illustrating a circuit configuration of a system using the detection device according to the embodiment.

FIG. 4 is a block diagram schematically showing a circuit configuration of a system using a detection device of a comparative example.

FIG. 5 is a block diagram schematically showing the detection device proposed above.

[Explanation of symbols]

 52 Transmitter 54 Transmit pulse transmitter 56 Transmit antenna 58 Receive antenna 62 Sampling means 64 Phase shift means 68 Voltage variable phase shift circuit 72 Sampling pulse generator 74 Signal processing means

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hideki Hayakawa 4-1-2, Hirano-cho, Chuo-ku, Osaka-shi, Osaka Inside Osaka Gas Co., Ltd. (72) Inventor Ikuo Arai 1-48-31 Funabashi, Setagaya-ku, Tokyo

Claims (4)

[Claims] A transmitter for generating a transmission signal of a predetermined frequency; a transmission pulse generator for generating a transmission pulse signal in relation to the transmission signal from the transmitter; and the transmission from the transmission pulse generator. A transmitting antenna for transmitting an electromagnetic wave based on a pulse signal toward an underground concealed object, a receiving antenna for receiving a reflected wave from the underground concealed object, and a phase of the transmitted signal from the transmitter. Phase shifting means for variably delaying as required, a sampling pulse generator for generating a sampling pulse in relation to the transmission signal delayed by the phase shifting means, and a sampling generated by the sampling pulse generator Sampling means for sampling the received signal received by the receiving means based on the pulse; and sampling by the sampling means. An underground concealed object detection device, comprising: signal processing means for lowering the frequency of the coupled received signal to detect the position of the underground concealed object. 2. The underground concealment according to claim 1, wherein the transmission signal generated by the transmitter is transmitted at a frequency of 1 MHz or more, and the received signal sampled by the sampling means is integrated. Object detection device. 3. The underground concealed object according to claim 2, wherein a delay amount of the transmission signal by the phase shifting means is 1 to 1000 ns, and is in a range covering one cycle of the transmission signal. Detection device. 4. A transmission signal having a predetermined frequency is generated by a transmitter, a transmission pulse signal is generated by a transmission pulse generator in relation to the transmission signal, and an electromagnetic wave based on the transmission pulse signal is concealed from a transmission antenna underground. Transmitted to the object, and the reflected wave from the underground concealment object is received by a receiving antenna, and the phase of the transmitted signal is delayed as required by phase shifting means, and the phase of the transmitted signal is related to the delayed transmitted signal. Then, a sampling pulse is generated by a sampling pulse generator, the received signal is sampled by sampling means based on the sampling signal, and then the received signal sampled is integrated by signal processing means to determine the position of the underground concealed object. A method for detecting an underground concealed object, wherein the method comprises detecting.