JPH05196729A - Underground structrue investigating radar - Google Patents

Abstract

PURPOSE:To detect an object irrespective of a buried direction of an underground structure by directing antenna elements toward directions which are different by 120 deg. from one another, sequentially switching an element to be used to gradually polarize a polarized direction and obtaining scattering matrix elements from the obtained data. CONSTITUTION:Three dipole antennas rotate with polarized surfaces which are different by 120 deg. from one another. Distance pulses generated from rotary encoders 11a, 11b attached to wheels are input via a twin encoder circuit 11c into a radar controller 12, where three polarization switching pulses are generated and two antennas are sequentially selected by an antenna switching device 16 so that one is for reception and the other is for transmission. A switching pulse is generated so that electric waves are transmitted from a transmission circuit 13 for a predetermined time and they are received by a reception circuit 14 simultaneously. This reception data is processed in a signal processor 25 to obtain scattering matrix elements, and a direction of an underground structure can be distinctly detected from the obtained components. In addition, received scattering matrix data is rotated by an optional angle so that reception data can be obtained irrespective of the buried direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an underground buried object exploration radar for searching an underground buried object from the ground.

[0002]

2. Description of the Related Art Conventionally, various methods have been proposed for exploring buried objects in the ground, but basically, pulse waves such as electromagnetic waves or ultrasonic waves are emitted into the ground and reflected from the buried objects. It depends on the method of detecting the reflected waves that have been received.

[0003]

However, in such a conventional method, since the polarization direction of the electromagnetic wave radiated from the antenna is fixed, when the buried object and the polarization direction are different from each other, reflection occurs. The problem was that the waves were weak and in some cases they could not be detected.

[0004]

In order to solve the above problems, the present invention focuses on a certain point outside the antenna.
Three antenna elements arranged at positions shifted by degrees, a rotary encoder that generates a distance pulse each time the vehicle travels a predetermined distance, a first switching pulse, a second switching pulse each time the distance pulse occurs, A radar controller that sequentially generates a third switching pulse, and a polarization switching circuit that selects an arbitrary antenna element for transmission and another antenna element for reception and changes the combination of the antenna elements each time a switching pulse is generated. A transmitting circuit and a receiving circuit that transmit and receive electromagnetic waves by the selected antenna element, and a signal processor that performs a predetermined calculation based on data obtained from the sequentially selected antenna elements to obtain a scattering matrix element. It is equipped with.

[0005]

Since the antenna elements are oriented in different directions by 120 degrees and the antenna elements used are switched sequentially, the polarization direction is changed every moment and the scattering matrix element is obtained from the obtained data. It is possible to distinguish and detect a buried object having a property and a buried object having no direction.

[0006]

1 is a plan view showing the structure of an antenna used in this apparatus. In the figure, reference numerals 1 to 3 denote dipole antennas each having a triangular metal plate as an element and having their vertices facing each other. Each dipole antenna has a polarization plane indicated by an arrow, and a dipole antenna is centered on a point A outside the antenna. As shown in the figure, the polarization planes are arranged so that they are rotated by 120 degrees each and rotated.

FIG. 2 shows a radar device which transmits and receives radio waves via this antenna. In FIG. 2, reference numeral 4 is a radar sensor unit, and 5 is a signal processing unit. The radar sensor unit 4 is a rotary encoder 1 provided with wheels 20 and 21 on the left and right respectively.
1a and 11b, the rotary encoder 11a,
11b generates a distance pulse as shown in FIG. 3 (a) every time it travels a predetermined distance.

The distance pulse generated from the rotary encoders 11a and 11b is supplied to the twin encoder circuit 11c, and the difference in the rotational speeds of the left and right wheels and the traveling distance thereof are detected, and this information is used by the radar controller 1 for overall control.
2 is supplied. As a result, the radar controller 12 selects one of the transmitting circuit 13 for transmitting radio waves, the receiving circuit 14 for demodulating the reflected waves from the ground, and the antennas 1 to 3 by the method described later, and the other one. One of the antenna switching circuits 16 is connected to the receiving circuit 14 and is controlled.

The received radar signal and the output signal of the twin encoder circuit are transmitted by the radar controller 12 through the electric / optical conversion circuit 22 to the optical fiber cable 23.
And is transmitted to the signal processing unit 5 which is a separate body. In the signal processing unit 23, the signal supplied to the signal processor 25 via the optical / electrical conversion circuit is subjected to signal processing, recorded by the data recording device 26, and displayed by the CRT 27. The symbol 28 is a battery.

The operation of the device configured as described above is as follows. As the device travels, the rotary encoders 11a and 11b attached to the wheels 17 generate distance pulses shown in FIG. 3 (a). The distance pulse is supplied to the radar controller 12 via the twin encoder circuit 11c, and under the condition that the period T is longer than a certain value, three polarizations are switched during the period as shown in FIG. 3 (b). Pulses are sequentially generated. This pulse is the antenna switch 16
As shown in Table 1, two antennas are sequentially selected from the three antennas as shown in Table 1.
One is for receiving and the other is for transmitting.

[0011]

[Table 1] In Table 1, the transmitting antenna and the receiving antenna may be reversed. Alternatively, the other two signals that are not used for reception but for transmission may be periodically used to combine the two signals.

Therefore, each time the switching pulse is generated, the transmitting antenna and the receiving antenna are switched. Then, the radar controller 12 controls the transmitting circuit 13 as shown in FIG. 3C for a predetermined time after the switching pulse is generated to transmit the radio wave. Then, at the same time as the transmission of the radio wave, the receiving circuit 14 is controlled to operate the receiving circuit 14 for a predetermined time. The transmission and reception times are set shorter than the time until the next switching pulse is generated.

In this way, the polarization of the transmission rotates every 120 degrees, and the polarization of the reception also has a phase difference of 120 degrees with respect to 1
Since it rotates every 20 degrees, radio waves are transmitted in all directions and reflected waves are received in all directions. Therefore, in the conventional device, the polarization direction was fixed, so it could be difficult to detect depending on the embedding direction.However, this device detects the embedding object in any embedding direction because the polarization direction changes from moment to moment. can do.

The signal demodulated by the wave receiving circuit 14 and the distance pulse from the rotary encoder 11 are supplied to the signal processor 25, and the information of the buried object corresponding to the trajectory and distance of the radar sensor is detected. Even if the signal obtained from the receiving antenna is used as it is, the desired purpose can be achieved because the polarization direction rotates, but by calculating the scattering matrix in the signal processor 25 as follows,
Further efficient detection can be performed, and this part is the gist of the present application.

Assuming x and y axes that are orthogonal to the ground surface, the transmission and reception signals of the radar have the following scattering matrix relationship. In the formulas below, the underlined ones represent the matrix amount, and the non-underlined ones represent the scalar amount. Although it is anomalous in relation to the format, it is described with an underline).

S = S _ij (t) (1) where i and j are the values 1 and 2 of the numbers, and the components in the x or y direction The equation (1) can be expanded as the equation (2).

[0017]

[Equation 1] Here, S ₁₁ is a component that emits radio waves of x-direction polarization and detects a reflected wave of x-direction polarization, S ₁₂ is a component that emits radio waves of x-direction polarization and detects a reflected wave of y-direction polarization, S ₂₁ Is a component in which a radio wave of y-direction polarization is emitted and a reflected wave of x-direction polarization is detected. S ₂₂ is y
This is a component that emits a directional polarized radio wave and detects a reflected wave of a y polarized wave.

The components from S ₁₁ to S ₂₂ must be obtained from the radar reception signal. Although the description of the guidance process is omitted because it becomes complicated, the conclusion is that the radar reception signals in modes 1, 2, and 3 are f ₁ (t), f ₂ (t), and f, respectively.
_{If 3} (t), the signal processor 25 may perform the operations of the expressions (3) to (6). _{S 11 (t) = - {} f 1 (t) + f 3 (t)} ··········· (3) S 12 (t) = - {f 1 (t) + 4f 2 (t _{) + f 3 (t)}} / 3 ·· (4) S 21 (t) = S 12 (t) ··················· (5) S 22 ( t) = {f ₁ (t) -f ₃ (t)} / 3 ^1/2 ... (6)

Among the respective components of the scattering matrix obtained in this way, S in which the polarization directions of the transmitted and received radio waves are the same
₁₁ (t) and S ₂₂ (t) are suitable for the measurement of buried objects having no directional component in the ground, that is, those having omnidirectional components such as strata or cavities. In addition, S ₁₂ (t) and S
₂₁ (t) is suitable for measurement of buried objects having a specific directional component in the ground, that is, such as buried pipes.

When investigating a buried pipe, it is not known in which direction the buried pipe is buried. For example, when the buried pipe is orthogonal to the polarization direction of the transmitted radio wave, the transmitted radio wave is transmitted. Does not reflect from the buried pipe, the reflected wave cannot be detected. Further, when the polarization direction of the transmitted radio wave is parallel to the embedding direction of the buried pipe, the radio wave is reflected by the buried pipe, but the polarization direction of the received radio wave is orthogonal to the reflected wave, so that the reflected wave cannot be detected. For this purpose, if the polarization direction and direction of the radio wave and the buried direction of the buried pipe are kept at 45 degrees, the maximum reception level can be obtained.

For this purpose, the scattering matrix may be coordinate-converted. That is, the calculation of the equation (7) may be performed.

[Equation 2]

As described above, by obtaining the data obtained by rotating the received scattering matrix data by the arbitrary angle θ, the received data can be obtained regardless of the embedding direction of the embedding pipe. Therefore, the S / N ratio is good if the received data is collected and the angle that maximizes the signal obtained while changing the angle θ is analyzed at the time of analysis, without considering the direction in which the buried pipe is buried during measurement. You can get a signal.

FIG. 4 is a flow chart showing the operation when the above processing is performed by the computer. In FIG.
Enter the data in step 100 and step 10
In step 1, the scattering matrix S is calculated according to equations (3) to (6), and in step 102, the scattering matrix S (θ) in the coordinate system rotated by the angle θ in equation (7) is calculated. Then, the processing result is displayed in step 103, and if it is sufficient, the ending process is performed in step 104. However, if this is not sufficient, the ending process is not performed, a new angle θ is input in step 105, and the process after step 102 is performed again.

This device is divided into a radar sensor section 4 and a signal processing section 5. The signal processing section 5 can be stored compactly when not in use when placed on a folding cart as shown in FIG. 5 (a). Can be freely performed. In FIG. 5, reference numeral 50 denotes a light-shielding cover, which prevents reflection on the CRT and makes it easy to see. Also, the power supply unit can be pulled out in the direction of the arrow. A lock mechanism is provided near the cart wheels as shown in FIG. 5 (b), and when stored, the pins 51, 5 are provided as shown in FIG. 5 (b).
Remove 2 and rotate the wheel to the rear wheel side as shown in FIG. 5 (c) to fold it as shown in FIG. 5 (d).

[0025]

As described above, the present invention provides 120
Since two of the three antenna elements that are rotated by being shifted by degrees are sequentially selected to transmit and receive the radio wave, the polarization planes of the transmitted and received radio waves change every moment, and the first invention is based on this data. Since the scattering matrix element is obtained from the obtained data, it is possible to detect the embedded object having directionality and the embedded object having no directionality separately, and the second aspect of the invention is to calculate the coordinate axes of the scattering matrix obtained in the first aspect of the invention. Since it is rotated, there is an effect that even an embedded object having a direction can be detected in the best state.

[Brief description of drawings]

FIG. 1 is a plan view of an antenna used in the present invention.

FIG. 2 is a block diagram showing an embodiment of the present apparatus.

FIG. 3 is a waveform diagram of each part of the apparatus of FIG.

FIG. 4 is a flow chart showing an operation when controlling the apparatus by a computer.

FIG. 5 is a diagram showing a configuration of a folding cart.

[Explanation of symbols]

 11 Rotary Encoder 12 Radar Controller 13 Wave Sending Circuit 14 Wave Receiving Circuit 15 Signal Processor 16 Polarization Switching Circuit 17 Wheels

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Noriaki Kimura 3-16-1, Tambara, Tamano-shi, Okayama Mitsui Engineering & Shipbuilding Co., Ltd. Tamano Research Institute (72) Inventor Kanji Murasawa 3-16, Tambara, Tamano-shi, Okayama No. 1 Mitsui Engineering & Shipbuilding Co., Ltd. Tamano Research Institute (72) Inventor Chihiro Kamimuta 3-161-1 Tambara, Tamano City, Okayama Prefecture Mitsui Shipbuilding Co., Ltd. Tamano Research Laboratory (72) Inventor Massei Konishi 3 Tamahara, Tamano City, Okayama Prefecture No. 16-1 Mitsui Engineering & Shipbuilding Co., Ltd. Tamano Research Institute

Claims (1)

[Claims] 1. 120 around a certain point outside the antenna
Three antenna elements arranged at positions shifted by a degree, a rotary encoder that generates a distance pulse each time the vehicle travels a predetermined distance, a first switching pulse, a second switching pulse each time the distance pulse occurs, A radar controller that sequentially generates a third switching pulse, and a polarization switching circuit that selects an arbitrary antenna element for transmission and another antenna element for reception and changes the combination of the antenna elements each time a switching pulse is generated. And a transmitting circuit and a receiving circuit that transmit and receive electromagnetic waves by the selected antenna element, and a signal processor that performs a predetermined calculation based on the data obtained from the sequentially selected antenna elements and obtains a scattering matrix element. Underground buried object exploration radar characterized by being equipped with