JP2000121722A - Object detecting apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an object detecting apparatus which can reduce noise component and detect the position of an object with high precision. SOLUTION: This object detecting apparatus is equipped with a transmitting antenna 6 transmitting an electromagnetic wave toward a concealed object 8, a receiving antenna 10 receiving the electromagnetic wave reflected from the concealed object 8, a positive feedback amplifier 12 performing positive feedback of a signal received from the receiving antenna 10, a sampling means 14 for sampling the received signal subjected to positive feedback, and a signal processing means 38 which processes the received signal subjected to sampling and operates the position of the object. The positive feedback amplifier 12 performs sequentially positive feedback of the received signal during one measuring cycle, thereby reducing noise component of the received signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an object position detecting device for detecting the position of an object such as a buried pipe using electromagnetic waves.

[0002]

2. Description of the Related Art A detection device for detecting an underground concealed object (for example, a gas pipe, a water pipe, etc.) as an object is known. Such an object detection device includes a pulse transmitter that oscillates a pulse signal, a transmission antenna that transmits an electromagnetic wave underground based on an oscillation signal from the pulse transmitter, and a reflected electromagnetic wave from an underground concealed object. The system includes a receiving antenna for receiving, a sampling means for sampling a received signal received by the receiving antenna, and a signal processing means for performing arithmetic processing on the sampled signal as required.

[0003]

In this object detection device, a transmission signal transmitted to an underground concealed object is a high-frequency electromagnetic wave. When such a high-frequency electromagnetic wave is used,
The signal level of the received signal received by the receiving antenna is weak, which makes it difficult to detect the position of the underground concealment object with high accuracy.

[0004] Such a problem is caused not only by an object detection device that detects the position of an underground concealed object using electromagnetic waves, but also by a stationary object such as a building (building, tower, bridge), an automobile, a ship, an airplane, or the like. There is also an object detection device that detects the position of a moving object. SUMMARY OF THE INVENTION An object of the present invention is to provide an object detection device capable of detecting a position of an object with high accuracy by reducing noise components.

[0005]

According to the present invention, a transmitting antenna for transmitting an electromagnetic wave toward an object, a receiving antenna for receiving an electromagnetic wave reflected from the object, and a signal received from the receiving antenna are transmitted by a predetermined feedback circuit. A feedback amplifier for amplifying, a sampling means for sampling a positive-feedback received signal, and signal processing means for processing the sampled received signal to calculate a position of an object, wherein the positive feedback amplifier has one measurement cycle. And wherein the reception signal is sequentially subjected to positive feedback amplification.

According to the present invention, a positive feedback amplifier is interposed between the receiving antenna and the sampling means, and the positive feedback amplifier converts a received signal transmitted from the receiving antenna to the sampling means during one measurement cycle. Positive feedback amplification is performed sequentially. Therefore, while the signal component of the received signal is amplified by the positive feedback amplification of the received signal, the noise component is suppressed, and thus a received signal having a small noise component is obtained, and the position of the object is detected with high accuracy. can do. In particular, since the received signals are sequentially amplified by positive feedback, the amplification becomes large in the latter half of one measurement cycle, and the amplification effect becomes large.

For example, when sampling a received signal after positive feedback for a predetermined number of times, the entire sampled received signal is amplified by positive feedback, and the noise component of the entire signal is suppressed. Further, when sampling a received signal while performing positive feedback amplification, the number of times of positive feedback amplification increases in the latter half of one measurement cycle, whereby the noise component is suppressed in the latter half of the received signal. If the object is located away from the transmitting antenna and the receiving antenna, the time required for the electromagnetic wave transmitted from the transmitting antenna to be received by the receiving antenna becomes longer, the received signal level decreases, and the position of the object decreases. Although it is difficult to detect with high accuracy, when sampling with positive feedback amplification, the received signal of the electromagnetic wave reflected from an object located at a position distant from the transmitting antenna and the receiving antenna suppresses the noise component, and particularly, The position of such an object can be relatively easily detected with high accuracy.

Further, the present invention provides a transmitting antenna for transmitting an electromagnetic wave toward an object, a receiving antenna for receiving an electromagnetic wave reflected from the object, a sampling means for sampling a received signal from the receiving antenna, Variable low-pass filter means for removing a noise component of the received signal, and a signal processing means for processing the received signal passed through the variable low-pass filter means to calculate the position of the object, the variable low-pass filter means, During one measurement cycle, the time constant increases with time.

According to the present invention, a variable low-pass filter is provided between the sampling means and the signal processing means, and the variable low-pass filter has a time constant that increases with time during one measurement cycle. Become. Therefore, the time constant is small at the beginning of one measurement cycle, and the variable low-pass filter means hardly affects the signal components. Then, in the latter half of one measurement cycle, the time constant gradually increases, and the variable low-pass filter means gradually removes even low-frequency signal components (signals such as random noise) from high-frequency components, and thus the received signal with small noise components. Is obtained. In particular, if the object is located at a position distant from the transmitting antenna and the receiving antenna, the time required for the electromagnetic wave transmitted from the transmitting antenna to be received by the receiving antenna becomes longer, and the received signal level decreases, and Although it is difficult to detect the position of the electromagnetic wave with high accuracy, the use of the variable low-pass filter means that changes the time constant as described above allows the electromagnetic wave reflected from an object at a position distant from the transmitting antenna and the receiving antenna. The more the received signal, the more the noise component is removed, and the position of such an object can be detected with high accuracy.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an object detection device according to the present invention will be described below with reference to the accompanying drawings. First Embodiment FIGS. 1 to 4 show a first embodiment of an object detection device according to the present invention, and FIG. 1 is a block diagram schematically showing the object detection device of the first embodiment. FIG. 2 is a block diagram schematically showing a positive feedback amplifier in the object detection device of FIG. 1, and FIG. 3 is a time chart showing various signals generated in the object detection device of FIG. a) ~
(D) is a diagram for explaining a sampling mode by a sampling unit of the object detection device of FIG. 1.

Referring to FIG. 1, the illustrated object detection device comprises:
It includes a transmitter 2, a transmission pulse generator 4, and a transmission antenna 6. The oscillator 2 is composed of, for example, a crystal oscillator, and generates an oscillation signal P1 having a predetermined frequency. The oscillation signal P1 from the transmitter 2 may be, for example, a sine wave (FIG.
reference). In order to detect underground concealed objects 8 such as buried gas pipes and buried water pipes at high speed and with high accuracy, the frequency of the oscillation signal P1 is increased, for example, to 1 MHz (H).
z) It is desirable to set the above.

The oscillation signal P1 from the oscillator 2 is sent to a transmission pulse oscillator 4, and the transmission pulse generator 4 generates a transmission pulse signal P4 when the oscillation signal P1 rises from zero and reaches a predetermined value V1. (See FIG. 3). Therefore, the transmission pulse signal P4 generated by the transmission pulse generator 4
Is the time T from the zero point of the rise of the oscillation signal P1.
Generated one delay later. The transmission pulse signal P4 is transmitted to the transmission antenna 6, and the transmission antenna 6 transmits an electromagnetic wave toward the underground concealed object 8 based on the transmission pulse signal P4.

[0013] The object detecting device also includes a receiving antenna 1
0, a positive feedback amplifier circuit 12, a sampling means 14, a sampling pulse generating means 16, and a pilot pulse generator 18. The reception antenna 10 receives the electromagnetic wave transmitted from the transmission antenna 6 and reflected by the underground concealment 8, and the received signal P 5 is supplied to the positive feedback amplifier 12. The receiving antenna 10, together with the transmitting antenna 6, is mounted on the front end of a propulsion body (not shown) that excavates and propells the soil. Since the reception signal P5 of the reception antenna 10 is a reception signal of an electromagnetic wave reflected from the underground concealment 8, it is a signal that is delayed with respect to the transmission pulse signal (see FIG. 3). 6 and the distance between the receiving antenna 10 and the underground concealment object are increased. The transmitting antenna 6 and the receiving antenna 10
It can be composed of a bowtie antenna known per se. Note that the transmitting antenna 6 and the receiving antenna 10 can be constituted by separate dedicated antennas, and that one antenna is configured to have both functions of the transmitting antenna and the receiving antenna by distinguishing the operation time. Can also.

Referring to FIG. 2, positive feedback amplifier 12 shown in FIG.
Is composed of an amplifier 20, delay means 22 and attenuator 24. Amplifier 20 amplifies the signal. The amplified signal is sent to the sampling means 14, and a part of the signal is sent again to the amplifier 20 through the delay means 22 and the attenuator 24, and the amplifier 20 is sent through the delay means and the attenuator 24. The signal fed back and the signal received from the receiving antenna 10 are added and amplified.
The delay means 22 delays the signal fed back via the attenuator 24 for a predetermined time. Further, the attenuator 24 attenuates the feedback signal. The positive feedback amplifier 12 and its related configuration will be described later in further detail. Although the positive feedback amplifier 12 is used in this embodiment, a feedback circuit that amplifies the signal by a predetermined feedback circuit may be used.

The transmission signal P1 from the transmitter 2 is sent to the sampling pulse generating means 16. The illustrated sampling pulse generator 16 includes a phase shifter 26, a pulsing circuit 28, and a sampling pulse generator 30. The phase shift means 26 is composed of a phase shift circuit voltage control circuit 32 and a variable voltage phase shift circuit 34, and a transmission signal P 1 from the transmitter 2 is sent to the variable voltage phase shift circuit 34. The phase shift circuit voltage control circuit 32 controls the voltage supplied to the variable voltage phase shift circuit 34. Further, the voltage variable phase shift circuit 34
Makes the phase of the transmission signal variable based on the control voltage from the phase shift circuit voltage control means 66. That is, the variable voltage phase shift circuit 34 increases the phase delay of the transmission signal (in other words, increases the delay time) as the control voltage from the phase shift circuit voltage control unit 32 increases, for example.
On the other hand, as the control voltage from the phase shift circuit voltage control means 32 decreases, for example, the phase delay of the transmission signal is reduced (in other words, the delay time is shortened). As such a voltage variable phase shift circuit 34, for example, 30 to 200
A circuit in which about five pF varicaps are incorporated can be used. In such a circuit, by changing the voltage, for example, from 0 to 5 V, the phase of the transmission signal P1 can be changed, for example, from 0 to 60 × 10 ^−9. Seconds (0-60 ns)
Can be delayed.

The phase shifter 26 generates the phase shift signal P2 (see FIG. 3) as described above. This phase signal P
2 is a signal delayed by a predetermined time T phase from the transmission signal P1, and the control voltage supplied to the voltage variable phase circuit 34 is changed to control the phase delay time with the transmission signal P1.

The phase shift signal P2 from the phase shift means 26 is sent to a pulsing circuit 28, which pulsates the phase shifting signal. The pulsed phase-shifted signal is then sent to a sampling pulse generator 30, which samples the phase-shifted signal P
2, the sampling pulse signal P3 (see FIG. 3)
Generate In this embodiment, as shown in FIG. 3, a sampling pulse signal P3 in which the output of the phase shift signal P2 from the phase shift means 26 becomes a predetermined value V2 is generated. That is, the sampling pulse generator 30 generates a 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 14. The sampling pulse signal P3 generated by the sampling pulse generator 30 is set very short.

The last one of the sampling pulse signals P3 from the sampling pulse generator 30 in one measurement cycle functions as the gate signal of the sampling means 14, and the sampling means 14 receives the signal from the sampling pulse generator 30 for one measurement cycle. When the last sampling pulse signal P3 is transmitted, the reception signal received by the reception antenna 10 and positively amplified by the positive feedback amplifier 12 is incorporated.

The transmission signal P1 transmitted from the transmitter 2 is
Further, it is sent to the pilot pulse generator 18. Pilot pulse generator 18 generates a pilot pulse signal based on signal P1. This pilot pulse signal is sent to the positive feedback amplifier 12, added to the received signal from the receiving antenna 10, and then amplified by the amplifier 20. This pilot pulse signal is desirably added at the end of the measurement period of one pulse-like transmission signal, in other words, at the end of one search signal. By adding in this manner, the search signal and the pilot pulse are added. Signals can be easily distinguished. The pilot pulse signal does not need to be added at the end of the above-described measurement period, but can be added at an arbitrary time that is easy to distinguish from the search signal.

In this embodiment, the positive feedback amplification by the positive feedback amplifier 12 and the sampling means 1 are performed as follows.
4 is performed. Mainly FIGS. 1 and 3
Referring to FIG. 4 and FIG. 4, the frequency of transmission signal P1 generated by transmitter 2 is set to, for example, 20 MHz, and its cycle is 50 ns. In such a case, for example, 312.
During one measurement cycle set to 5 μs, the phase shifting means 26
Generates a phase-shifted signal delayed by a predetermined time T from the transmission signal P1, and based on the phase-shifted signal P2, the sampling pulse generation 30 generates 6250 sampling pulse signals P
3 is generated.

The sampling pulse generator 30 has 6249
While generating the number of sampling pulse signals, the positive feedback amplifier 12 sequentially positively amplifies the received signal P5 as understood from FIGS. 1 and 4A. And 6250
When the sampling pulse signal is generated, as shown in FIGS. 3 and 4 (b), the sampling means 14 performs sampling measurement of the 6250th received signal which has been positively feedback amplified based on the sampling pulse signal. Then, the measured sampling signal P6 (see FIG. 3) is sent from the sampling means 14 to the downstream side. Note that each signal in FIG. 4A indicates an output signal of the positive feedback amplifier 12, and a component a of each signal is a direct wave component received directly from the transmitting antenna 6 to the receiving antenna 10. Component b of
Is a reflected wave component reflected from the underground covert object 8 and received by the receiving antenna 10, and those components c are pilot signal components sent from the pilot pulse generator 18.

The positive feedback amplification of the received signal P5 is performed as follows. That is, the delay unit 22 outputs a signal fed back from the amplifier 20 via the delay unit 22 and the attenuator 24 (the K-th signal Sk subjected to positive feedback amplification) and the next received signal [(K + 1 ) -Th received signal] is delayed for a predetermined time so that the signal overlaps with the signal. Further, the attenuator 24 includes the delay circuit 2
2, the magnitude of the amplitude of the signal fed back through K (positive feedback amplified Kth signal Sk) with respect to the pilot signal and the next received signal [(k
The signal to be fed back is attenuated as required so that the magnitude of the pilot signal added to [+1) -th received signal] is the same. At this time, a pilot signal from pilot pulse generator 18 is used,
The magnitude of the pilot signal component of the feedback signal,
The attenuator 24 attenuates the whole signal to be fed back at a variable ratio so that the magnitude of the pilot signal added to the received signal is the same. By sequentially performing positive feedback amplification of the reception signal P5 many times in this manner,
A noise component included in the entire received signal can be suppressed, and thereby the position of the underground object can be detected with high accuracy.

When the sampling in the first (n = 1) measurement cycle is completed, the sampling in the second (n = 2) measurement cycle is performed. In the second measurement cycle, the phase shift circuit voltage control means 3
2 makes the voltage supplied to the variable voltage phase shift circuit 34 somewhat larger, for example, whereby the phase shift signal P2 from the phase shift means 26 has a time (T + ΔT) phase delay from the transmission signal P1. The next 31 following the first measurement cycle
During the measurement cycle of 2.5 μs, the phase shift means 26 outputs the phase shift signal P having a time (T + ΔT) phase delay from the transmission signal P1.
2, and the sampling pulse generator 30 generates 6250 sampling pulse signals P3 based on the phase shift signal P2 in the same manner as in the first measurement cycle. Note that the time ΔT for sequentially sending is, for example, 0.117
ns.

In the second measurement cycle, the first measurement cycle
Similarly to the measurement cycle, while the sampling pulse generator 30 generates 6249 sampling pulse signals, the positive feedback amplifier 12 sequentially positively amplifies the received signal P5. Then, when the 6250th sampling pulse signal is generated, the sampling means 14 performs positive feedback amplification of 62 based on the sampling pulse signal.
The 50th received signal is sampled and measured, and the measured sampling signal P6 (see FIG. 4C) is sent from the sampling means 14 to the downstream side.

In this embodiment, as shown in FIG. 3, the reference measurement period is set to, for example, 80 ms. Therefore, from the start of the first measurement cycle to 80 ms, in this embodiment, for example, the 256th , During which the phase shift means 26 generates a phase shift signal P2 which is sequentially delayed by ΔT from the transmission signal P1, and a sampling pulse signal generated in relation to the phase shift signal P2. The sampling of the positive feedback amplified received signal is performed based on the last sampling pulse signal of each measurement cycle in P3. The reference measurement period,
The period of the measurement cycle can be appropriately set according to the frequency of the transmission signal P1 and the like.

The object detecting apparatus further comprises a signal processing means 38 for calculating and processing the signal P6 sampled by the sampling means 14, and a display means 40 for displaying the position of the concealed object processed by the signal processing means 38. Contains. The signal processing means 38 has a memory 42, and the sampling signal P6 from the sampling means 14 is temporarily stored in the memory 42, and the signal processing means 38 is a sampling signal sampled within the reference measurement period, which is 256 in this embodiment. Arithmetic processing is performed on the sampling signals as required, and a detection signal P7 (see FIGS. 3 and 4D)
Generate The detection signal P7 generated in this way is sent to the display means 40, and information on the embedment position of the concealment object 8 contained in the detection signal P7 is displayed on the display means 40. By observing the position information displayed in, the embedment position of the concealed object can be easily known. Note that a CRT, a liquid crystal display device, or the like can be used as the display unit 40.

The positive feedback amplification of the reception signal P5 of the reception antenna 10 and the sampling of the positive feedback amplified signal are shown in FIG.
(The configuration of the object detection device may be substantially the same as the configuration shown in FIGS. 1 and 2). Referring to FIG. 5, in this mode, positive feedback amplification and sampling are performed for each received signal. As shown in FIG. 5A, the first received signal in the reference measurement period is amplified by the positive feedback amplifier 12, and the amplified signal is sampled by the sampling means 14, and the sampled sampling signal is sampled. Is stored in the memory 42 of the signal processing means 38. A part of the amplified received signal is fed back, added to the next (second) received signal and amplified, and the amplified received signal is sampled by the sampling means 14 as shown in FIG. , And the sampling signal is stored in the memory 42.

In this mode, the phase shift means 26 generates a phase shift signal P2 which is sequentially delayed by .DELTA.T from the transmission signal P1, and outputs a sampling means for each sampling pulse signal P3 generated in relation to the phase shift signal P2. The sampling by 14 is performed, for example, 256 times. These sampling signals are stored in the memory 42 and the signal processing means 38
Calculates the sampling signal stored in the memory 42 as required to generate a search signal shown in FIG.
The contents of the search signal are displayed on the display means 40. still,
Positive feedback amplification by the positive feedback amplifier 12 is performed in the same manner as described above.

Even if such a method is used, since the reception signal of the reception antenna 10 is subjected to positive feedback amplification, its noise component can be reduced and the position of the concealed object can be detected with high accuracy. In particular, in the latter half of one measurement cycle (in this manner, one measurement cycle coincides with the reference measurement period), the number of positive feedback amplifications is increased, and thus the signal component of the received signal is amplified. The noise component is suppressed. The signal component of the received signal in the latter half of the measurement cycle is a signal component that takes time before being received by the receiving antenna 10 after being transmitted from the transmitting antenna 6, in other words, at a position distant from the transmitting antenna 6 and the transmitting antenna 10. This is a reflected wave component from the concealed object 8, and the reflected wave component becomes smaller as the distance increases, but the smaller the reflected component becomes, the more it is amplified, so that the measurement accuracy of the position of such a concealed object is improved. Can be. A high frequency amplifier may be inserted before and after the positive feedback amplifier 12 described above. Second Embodiment Next, a second embodiment of the object detection device according to the present invention will be described with reference to FIG. FIG. 6 is a block diagram schematically illustrating the object detection device according to the second embodiment. In the second embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

In the second embodiment, the positive feedback amplifier 1
2 (and associated pilot pulse generator 18)
, A high-frequency amplifier 52 is provided. The high-frequency amplifier 52 includes the receiving antenna 10 and the sampling unit 1.
4 and amplifies the received signal from the receiving antenna 10 at a high frequency and sends it to the sampling means 14.

The sampling means 14 and the signal processing means 3 for processing the sampled sampling signal
8, a variable low-pass filter means 54 is interposed. The variable low-pass filter means 54 has a function of permitting passage of a low-frequency signal but cutting off a high-frequency signal. This variable low-pass filter means 54
Can change its time constant, and for example, can change its time constant by changing its capacitance using a variable voltage capacitor. Further, for example, a variable cut-off frequency device may be simply used. Other configurations of the second embodiment are substantially the same as those of the first embodiment.

In the second embodiment, the receiving antenna 1
The received signal of 0 is processed in the following manner similar to the processing manner shown in FIG. The first received signal in each measurement cycle (in this embodiment, coincides with the reference measurement period)
The amplified signal is amplified by the high-frequency amplifier 52, and the amplified signal is sampled by the sampling means 14, and the sampled sampling signal is stored in the memory 42 of the signal processing means 38 through the variable low-pass filter means 54. The next (second) received signal is subjected to high-frequency amplification and then sampled by the sampling means 14 in the same manner as described above, and this sampling signal is stored in the memory 42 through the variable low-pass filter means 54. Further, the third (or fourth ...) received signal is processed in the same manner, and the sampling signal is stored in the memory 42 through the variable low-pass filter means 54. In the second embodiment, the phase shifter 26 generates a phase shift signal P2 that is sequentially delayed by ΔT from the transmission signal P1, and the sampling pulse generator 30 generates a sampling pulse signal based on the phase shift signal P2. The sampling means 14 performs sampling of the received signal for each sampling pulse signal, and the sampling by the sampling means 14 is performed, for example, 256 times. These sampling signals are stored in the memory 42, and the signal processing means 38 performs an arithmetic processing on the sampling signals stored in the memory 42 as required to generate a search signal, and the contents of the search signal are displayed on the display means 40. Is done.

In this embodiment, the time constant of the variable low-pass filter means 54 is switched so that the time constant increases with time during the measurement cycle. When the time constant is changed in this way, the time constant is small in the first half of each measurement cycle, and therefore the variable low-pass filter 5
4 removes only high-frequency noise components, and its time constant becomes large in the latter half of each measurement cycle. Therefore, the variable low-pass filter means 54 also removes low-frequency noise components, and thereby, especially the signal of the received signal. In the latter half of each measurement cycle in which the component becomes small, the removal of the noise component can be increased to improve the detection position accuracy of the concealed object.

Although the embodiment of the object detection device of the present invention has been described above, the present invention is not limited to such an embodiment, and various changes and modifications can be made without departing from the scope of the present invention. is there.

For example, in the illustrated embodiment, the sampling pulse signal is generated by using the phase shift means 26 composed of the phase shift circuit voltage control circuit 32 and the variable voltage phase shift circuit 34. However, the present invention can also be used in other manners for generating a sampling pulse signal, such as a manner for generating a sampling pulse signal using a variable period oscillator including a voltage controlled oscillator (VCO).

Further, for example, in the illustrated embodiment, the present invention has been described by applying to a device for detecting the position of an underground concealed object as an object. However, the present invention is not limited to this, and a stationary object such as a building or an automobile is used. It can be widely applied as an object detection device for detecting the position of a moving object.

[0037]

According to the object detecting device of the first aspect of the present invention, the signal component of the received signal is amplified by the positive feedback amplification of the received signal, while the noise component is suppressed, and thus the noise component is suppressed. A received signal with few components is obtained,
The position of the object can be detected with high accuracy. In particular, since the received signals are sequentially amplified by positive feedback, the amplification becomes large in the latter half of one measurement cycle, and the amplification effect becomes large.

According to the object detecting apparatus of the second aspect of the present invention, the time constant of the variable low-pass filter means is small at the beginning of one measurement cycle to remove high-frequency signal components, In the latter half of the period, the signal component becomes large, and even a signal component having a small frequency is removed. Thus, a received signal having a small noise component is obtained. In particular, the received signal of an electromagnetic wave reflected from an object that is farther from the transmitting antenna and the receiving antenna has more noise components removed, and the position of such an object can be detected with high accuracy.

[Brief description of the drawings]

FIG. 1 is a block diagram schematically showing a first embodiment of an object detection device according to the present invention.

FIG. 2 is a block diagram schematically showing a positive feedback amplifier in the object detection device of FIG.

FIG. 3 is a time chart showing various signals generated in the object detection device of FIG. 1;

FIGS. 4 (a) to 4 (d) are diagrams for explaining a sampling mode by a sampling unit of the object detection device of FIG. 1;

FIGS. 5A to 5D are diagrams for explaining another example of a sampling mode by a sampling unit. FIGS.

FIG. 6 is a block diagram schematically showing a second embodiment of the object detection device according to the present invention.

[Explanation of symbols]

 Reference Signs List 2 transmitter 4 transmission pulse generator 6 transmission antenna 8 concealed object 10 reception antenna 12 positive feedback amplifier 14 sampling means 16 sampling pulse generator 18 pilot pulse generator 26 phase shift means 30 sampling pulse generator 38 signal processing means 54 variable low-pass Filter means

Claims (2)

[Claims] 1. A transmitting antenna for transmitting an electromagnetic wave toward an object, a receiving antenna for receiving an electromagnetic wave reflected from the object, a feedback amplifier for amplifying a signal received from the receiving antenna by a predetermined feedback circuit, and a positive feedback. Sampling means for sampling the sampled reception signal, and signal processing means for processing the sampled reception signal to calculate the position of the object.The feedback amplifier sequentially amplifies the reception signal during one measurement cycle. An object detection device, comprising: 2. A transmitting antenna for transmitting an electromagnetic wave toward an object, a receiving antenna for receiving an electromagnetic wave reflected from the object, sampling means for sampling a received signal from the receiving antenna, and noise of the sampled received signal. Variable low-pass filter means for removing the component, and signal processing means for processing the received signal passed through the variable low-pass filter means to calculate the position of the object, the variable low-pass filter means during one measurement cycle An object detection device characterized in that the time constant increases with time.