KR200188711Y1 - Antenna structure of detection apparatus for the survey of buried structures by used gpr system - Google Patents

Abstract

The present invention establishes the best underground buried surveying method to manufacture GPR which improves its performance, and also improves the work efficiency through small integration and develops and distributes economical and simplified GPR with greatly reduced cost. In order to provide the antenna structure of the underground buried probe using the GPR system to ensure the safety of the ground, in the underground buried probe using the GPR system, the transmitting antenna uses a dipole antenna, the center frequency of about 200MHz An antenna is used, and a plurality of transmitting / receiving antennas are formed so that the echoes of the received pulses are rapidly represented by several hyperbolas with respect to space and time while quickly passing through the target of one point while transmitting to the medium evenly side by side. Take the vertices of these hyperbolic curves to find the target of one point, Further configure a resistive terminator in the receiving antenna.

Description

ANTENNA STRUCTURE OF DETECTION APPARATUS FOR THE SURVEY OF BURIED STRUCTURES BY USED GPR SYSTEM}

The present invention relates to the antenna structure of the underground buried ground detection device, and more specifically to the ground penetration radar (GPR), which can compensate for the disadvantages of the pipe locator of the prior art (hereinafter referred to as GPR) It relates to an antenna structure of the underground buried surface detection device used.

In the basement of our residence, there are numerous underground structures such as gas pipes, water and sewage pipes, oil pipes, communication and power cable pipes, various ducts and storage tanks. Accordingly, safety accidents associated with underground facilities are frequent. This trend is also expected to continue to increase in the future. Therefore, careful management and maintenance of these underground facilities is urgent.

In Korea, the high-pressure pipe network of 10 ~ 70㎏ / ㎠ operates over 1,300 km as of the end of 1997 and is expected to reach 2,000 km within a few years. Due to the nature of the high-pressure pipes, large-scale accidents such as the Ahyeon-dong accident in 1994 occur, which requires thorough management and safety measures.

There are various factors that can cause the safety of the pipe, but among them, 1) pipe breakage by other construction (excavator, drilling machine), 2) pipe deformation due to ground subsidence or flow, 3) subway or other underground The three major hazards are electrical corrosion caused by vagus currents from the facility.

In order to establish countermeasures, it is essential to first identify the exact location of the pipe. In order to reduce the risk of other constructions, it is best to identify and notify the exact location of the gas piping when permitting before construction. In addition, accurate positioning of the pipe is essential to know the amount of deformation due to settlement or flow of the pipe.

Currently, the following methods are mainly used to locate the pipes.

1) The surface of stone is installed at the critical point (pipe section, before and after crossing).

2) Place plumbing signs directly above the plumbing or on the side road shoulders.

3) Use pipe locator.

The use of paving stones is ineffective because the installation intervals between the paving stones are too long and sometimes out of the original position, and the signing method does not indicate the exact position of the pipes, but it indicates the presence of high-pressure pipes around. to be.

The method of using a pipe locator is the most commonly used method, which has the advantage of being relatively accurate and simple. However, the accuracy of the pipe locator is greatly reduced due to interference in the place where the pipe is complicated.

One of the methods that can compensate for the disadvantages of the pipe locator is a method using the GPR.

GPR is a device that detects various structures and layers in the ground using high frequency electromagnetic wave and received signal processing method to detect the position of the object. It was originally used for the purpose of physics exploration and recently applied to underground pipe detection. It was.

However, such a conventional GPR is complicated in equipment configuration and requires considerable experience and proficiency to accurately analyze the detection results, and the detection results are very sensitive depending on the properties of the soil. It is a difficult situation.

That is, as described above, the conventional GPR, despite its precision, has a disadvantage in that the detection result greatly depends on the electrical properties of the soil, and requires considerable skill in analyzing the detection result, and also is expensive equipment. Wide spread is difficult. In addition, it is composed of a main console (transmission console), a transmission antenna, a portable PC, a cable (cable), etc., takes up a considerable amount of space during work and is inefficient in terms of maintenance.

Therefore, the present invention has been made to solve the above problems, the purpose of which is to compare the principle, advantages and disadvantages of the prior art described above by establishing the best underground landfill detection technique to improve the performance of GPR In addition, to improve the work efficiency through compact integration, and to develop and distribute economical and simplified GPR with greatly reduced cost, it provides antenna structure of underground buried probe using GPR system which secured the safety of piping. have.

1 is a block diagram of the underground landfill detection device using a GPR system of the present invention.

2 is a control block diagram of FIG. 1 in more detail.

Figure 3 is a side perspective view of a cart equipped with the present invention.

4 is a perspective view of FIG.

5 is a view showing a basic method of obtaining a cross-sectional image of the underground buried of the present invention.

6 is a view showing a method of shaping an image of the present invention.

7 is a view showing the detection result of the present invention.

8 is a diagram showing the results when the gas is probed in the longitudinal direction of the pipe;

9 is a view showing the principle of measuring the depth of embedding according to the present invention.

10 is a view showing the detection results when using an antenna having a center frequency of 100 MHz and a center frequency of 50 MHz, respectively.

11 shows the directivity characteristics of a dipole antenna;

12 shows resonance characteristics of a dipole antenna.

13 is a detailed circuit diagram showing a transmission antenna of the present invention.

14 is a detailed circuit diagram showing a receiving antenna of the present invention.

<Explanation of symbols for the main parts of the drawings>

100: control device 110: receiving preamplifier

120: A / D converter 130: pulse generator

140: pulse transmission circuit 150: CPU

200: transmit antenna 300: receive antenna

400: display unit 500: power supply unit

900 transmission line

The antenna structure of the underground buried surface detection device using the GPR system according to the present invention for achieving the above object is to control the entire system, to record and store the signal transmitted from the receiving antenna to process the data in the room It is responsible for transferring data to the PC necessary for the purpose.The first time the signal is recorded in the control device, the digital sampling interval of the received signal, which is an analog signal, the total time range in which the signal is recorded, the stacking frequency, etc. Determining various variables required for the exploration, generating and amplifying pulses suitable for the determined variables, amplifying them, radiating them through the transmitting antenna, amplifying and recording the signals received through the receiving antenna, and per sampling interval and trace. A controller for determining a sampling interval and number; A transmitting and receiving antenna for emitting a pulse generated by the control device and receiving a signal reflected from the buried object after passing through the medium; A display unit for realizing the pulse data acquired by the control device as an image, and displaying a sectional view of a higher resolution by applying various implementation colors to a high-resolution screen for the processed data; A transmission line made of a coaxial cable or an optical cable to perform data transmission between the control device and the transmitting and receiving antennas, and to transmit a radar wave and receive a reflected wave in a minimum noise state; And supplying driving power to each of the parts, and using the GPR system, the underground buried property detection device including a power supply using a DC power source to reduce the generation of high-quality pulses and noise as a necessary power for the generation of electromagnetic pulses and transmission and reception of data. In the transmitting antenna, a dipole antenna is used, but an antenna having a center frequency of about 200 MHz is used.

In addition, a plurality of transmitting and receiving antennas are constructed so that the echoes of pulses received by rapidly passing through a single target and appearing in multiple hyperbolas with respect to space and time are transmitted equally and side by side from the antenna. It is desirable to take a vertex and find one target.

In addition, it is more preferable to further configure a resistive termination device in the transmission and reception antenna.

Hereinafter, with reference to the accompanying drawings will be described in detail a preferred embodiment of the present invention.

The present invention radiates an electromagnetic radio wave in the frequency range of about 1 to 1800 MHz from the transmitter to the ground, and is reflected at the interface between the underground media (for example, the buried structure and soil contact) having different electrical characteristics. It is a non-destructive detection equipment that collects and records the electromagnetic waves returning to the ground and analyzes the image and structure of underground buried materials through data processing and analysis process by PC.

Figure 1 is a block diagram of the underground buried surface detection device using a GPR system of the present invention. In addition, Figure 2 is a control block diagram showing Figure 1 in more detail, Figure 3 is a side perspective view of a cart equipped with the subject innovation, Figure 4 is a perspective view of FIG.

As shown, the subject innovation consists of the control device 100, the transmitting antenna 200, the receiving antenna 300, the display unit 400, the power supply unit 500 and the transmission line 900.

The main control unit 100 controls the entire system, and records and stores a signal transmitted from the reception antenna 300 to transmit data to a PC necessary for data processing indoors. In particular, the controller 100 determines various variables required for the exploration, such as the initial time at which the signal is recorded, the digital sampling interval of the received signal, which is an analog signal, the total time range at which the signal is recorded, and the stacking frequency. After generating and amplifying a transmission and reception pulse suitable for the determined variable, the radiation is transmitted through the transmission antenna 200, and the signal received through the reception antenna 300 is amplified and recorded. In addition, the sampling interval and the number and sampling intervals per trace are determined.

Transmitter and receiver antenna (200) (300) is the most essential part of the GPR to emit a pulse generated from the control device 100 and receives the signal reflected back from the buried object after passing through the medium Is a device that uses different antennas depending on the emission frequency selected to match the exploration limit depth.

The display unit 400 is an apparatus for implementing the acquired pulse data as an image, and may display a sectional view of higher resolution by applying various implementation colors to a high resolution screen on the processed data.

The transmission line 900 is responsible for data transmission between the control device 100 and the transmission and reception antennas 200 and 300. The transmission line 900 receives the transmission of the radar wave and the reception of the reflected wave in the lowest noise state. It is preferable to use a coaxial cable or an optical cable in charge of the transmission function.

The power supply unit 500 preferably uses a DC power source in order to reduce the generation of high-quality pulses and noise as the necessary power for the generation of electromagnetic pulses and the transmission and reception of data.

The control device (100) comprises: transmitting means for generating a pulse of ultra wide bandwidth through a pulse generator (130) and a pulse transmitting circuit (140); A reception preamplifier (110) for amplifying a signal input from the reception antenna (300); An A / D converter 120 for converting an analog signal amplified by the reception preamplifier 110 into a digital signal; And a CPU 150 for controlling the entire system, collecting raw data, and measuring propagation time from transmission to reception.

In addition, the present invention, as shown in Figure 3 and 4, the control device 100, the transmitting antenna 200, the receiving antenna 300, the display unit 400, the power supply unit 500 and the transmission line 900 ) Is loaded on a cart 800 provided with a moving wheel 830 and a handle 820 to reduce mobility of the worker because of improved mobility.

Transmitting and receiving antennas 200 and 300 are installed in the lower cart 810 in order to minimize the transmission and reception signal (signal) loss, close to the surface and attached to the front, back so that electromagnetic waves are not lost in the air, light weight and workability good.

In addition, since the power supply unit 500 can be driven by a lightweight battery, the power supply unit 500 can be recharged, and battery replacement is easy. The display unit 400, which can display the information of the device to help the operator to quickly and smoothly detect, is made of a CRT monitor or LCD panel and has high resolution and high contrast ratio for sufficient reading even in direct sunlight in the open air. Have

When described with reference to the accompanying drawings, the principle of the invention of the present invention is configured as follows. First, the electromagnetic wave emitted from the transmitting antenna 200 propagates in the medium and detects a wave reflected after hitting an object, and measures the distance between the object and the transmitter from the flight time and propagation speed of the electromagnetic wave.

However, in the case of underground media, since the radar is physically non-homogeneous than the air propagated, it is difficult to easily find information such as radar. In other words, due to the physical heterogeneity, the signal reflected from the basement contains a lot of noise, which is difficult to read. Therefore, the exploration data must go through appropriate processing.

Basic method for obtaining a cross-sectional image of the underground buried using the present invention is as shown in FIG. In FIG. 5, (a) shows transmission and reception of electromagnetic waves, and (b) shows acquired pulse data.

As illustrated, a radio transmitter (XMIT) and a receiver form a pair of transmit / receive antennas 200 and 300 to be in contact with each other on the ground. The signal emitted from the transmitter penetrates a short distance into the ground. Radio waves, which propagate underground, will reflect when they collide with other materials with nearby soil and electrical properties. For example, signals are reflected from buried pipes and underground voids. The signal reflected from the underground object (radio signal) arrives after a short time after being emitted as shown in FIG.

FIG. 6 is a view illustrating a method of shaping an image of the present invention. In order to easily recognize a detector, a pulse echo reflected from a buried object is generally formed on a display unit 400 such as a PC screen. The radar moves on the ground at regular intervals as shown in Fig. 6 (a) (1 → 2 → 3), so that a new echo is drawn next to the previous echo as in Fig. 6 (b). This pulse pattern is continuously output on the screen of the PC. When a sufficient amount of signal is detected in this way, the operator can see the echo pattern on the screen and recognize that there is an object buried underground.

The above detection results are shown in the form of a hyperbola when the reflected pulses of the lower part of FIG. 7 (b) are connected. When the pipe is buried underground as shown in (a) of FIG. 7, when the buried object is located in front of the transmitting / receiving antennas 200 and 300 when it is detected across the pipe, the emitted echo is reflected back to the object. It will take some time to come.

This time is gradually reduced as the transmit and receive antennas 200 and 300 approach the object. If there are antennas 200 and 300 directly above the buried object, the echo reflection time is the shortest. Afterwards, the time for the reflected wave to reach the receiving antenna 300 increases as the buried object passes again. This results in a hyperbola. Experienced workers can see that this is a small object, such as a pipe. Different patterns appear depending on the type of buried structure. For example, a cuboid storage tank buried underground would appear as a flat curve with both ends of the echo curve descending downwards.

However, if the probe in the longitudinal direction of the pipe result will be as shown in FIG. That is, since the distance between the transmission and reception antennas 200 and 300 and the pipe are always the same, when the pulse of the received reflected wave is followed, it appears as a straight line. The problem is that the same results occur under different conditions. For example, assuming that the geological divisions such as the clay / bedrock layer are divided, the detection results are shown as straight lines as shown in FIG. 8 even in the disciplinary areas of the two layers. It cannot be said that it is buried. Therefore, when burying the buried pipe, it should be detected across the pipe.

Buried depth measurement principle according to the present invention is as shown in FIG. In other words, it is not easy to determine the depth of burial if you do not have some information about the surrounding soil. In principle, the GPR system measures the emission / arrival time of electromagnetic waves and pulses very accurately. In other words, if the moving speed of the electromagnetic wave in the soil is known, the depth of embedding can be calculated because the time between the transmitted pulse and the reflected pulse of FIG. 9 (b) is known. Therefore, the embedding depth is displayed on the image appearing on the PC through such a process.

However, the speed of the radar signal varies sensitively with the soil type. In the air, radar waves propagate at a rate of 297,600 km / sec. However, in the soil, the speed is very sensitive to the moisture content, porosity, etc. of the soil. Therefore, empirically knowing the electrical characteristics, electrical conductivity and dielectric constant (dielectric constant) of the soil, or if there is a buried object that knows the depth of embedding, it is possible to accurately correct the depth of embedding measured by GPR detection. Therefore, soil information is essential for accurate depth measurement through GPR. Table 1 shows the propagation characteristics of electromagnetic waves according to the general soil types.

material Dielectric constant Speed (m / ㎱) Attenuation Coefficient (㏈ / m) air One 0.30 0 distilled water 80 0.033 0.002 fresh water 80 0.033 0.1 sea water 80 0.01 1000 dry sand 3 ~ 5 0.15 0.01 saturated snad 20-30 0.06 0.03-0.3 limestone 4 ~ 8 0.12 0.4 ~ 1 silt 5-30 0.09 1-100 clay 5-40 0.07 1-100 granite 4 ~ 6 0.13 0.01 ~ 1 dry salt 5 ~ 6 0.13 0.01 ~ 1 ice 3 ~ 4 0.16 0.01

On the other hand, one of the most important variables in GPR survey is the selection of operating frequency. Appropriate frequency selection can determine whether or not exploration is successful. Frequency selection may be made by clearly defining the subject to be explored. This means that field exploration should be carried out prior to the survey.

Considerations for frequency selection include geological conditions of the site, surface obstructions, electrical characteristics of the soil, and depth of burial of the object. The most important factor in dual frequency selection is the depth of detection, because the higher the frequency, the lower the detection depth. Therefore, the frequency should be appropriately selected according to the depth and size of the target.

FIG. 10 is a detection result when an antenna having a center frequency of 100 MHz and a center frequency of 50 MHz is used, respectively. As can be seen, the information about the deep-depth buried material is relatively detailed when the low-frequency antenna of 50 MHz is used according to the depth of the object to be explored, and the information about the deep-depth buried material is used when the 100 MHz antenna is used. It can be seen that.

In addition, Table 2 below shows the approximate detectable depth according to the center frequency.

Depth (m) Center frequency (MHz) 0.5 1,000 1.0 500 2.0 200 7.0 100 10.0 50 30.0 25 50.0 10

When detecting the depth of gas pipelines, antennas with a center frequency of 225 MHz are mainly used.In addition, 400 MHz antennas are also used for the detection of other pipelines having a lower depth of field than gas pipelines at points where several pipes cross. However, since the depth of embedding of a general gas pipe is about 2m, it is most preferable to use an antenna having a center frequency of about 200MHz in the present invention.

In addition, a time window means how long a data is to be received, which is related to the depth of burial of the object to be detected. That is, the data must be received for a sufficient time more than the time when the electromagnetic wave propagates to the buried object and then returns again. This is also closely related to the propagation rate of electromagnetic waves in the soil. Therefore, when selecting the time window, it is necessary to know information about the electrical properties of the soil as well as the depth of embedding of the object.

Sampling interval (Sampling interval) means how much time interval to collect the reflected waveform to return, the value varies depending on the center frequency of the antenna used in general. The two variables are preferably used according to the frequency of the most suitable values according to the type of the transmit and receive antennas (200, 300).

In addition, if the electrical conductivity of the soil is high, the propagation of electromagnetic waves becomes difficult. In general, if the cell conductivity is 0.01Ω ^-1 · cm ^-1 or more, it is considered difficult to detect GPR. Therefore, it is essential to understand or predict the electrical characteristics of the area to be detected before the detection in advance. In Table 3 below, the media were classified according to their electrical conductivity.

Exploration conditions Electrical Conductivity (σ) (Ω ^-1 · cm ^-1 ) medium good σ <10 ^-7 Air, Dry Granite, Dry Limestone, Concrete, Asphalt Not bad 10 ^-7 <σ <10 ^-2 fresh water, ice, snow, sand, sit, dry clay, basalt Bad σ> 10 ^-2 Wet clay, wet basalt, sea water, thaw

Next will be described in more detail the operation of the present invention through the features of each component constituting the present invention.

Looking at the dipole antenna 200, 300 for transmission and reception of the present invention is as follows. In general, in the high frequency region, a horn antenna or a planar array type antenna is used. However, the dipole type antenna is used in the range of 225MHz that is the target of the present invention.

Dipole antennas have various problems such as low directivity, antenna ringing, unstable characteristic impedance, undesired frequency spread, and mechanical enlargement.However, the use of resistive termination reduces antenna resonance, It is possible to increase antenna directivity by adopting a reflector, to reduce unnecessary frequency spread by appropriate use of a buffer, and to reduce its size and weight.

11 and 12 show the characteristic investigation record of the dipole antenna for this improvement experiment. Here, FIG. 11 shows directivity characteristics of the dipole antenna, and FIG. 12 shows ringing characteristics of the dipole antenna.

The signal input from the receiving antenna 300 and amplified by the receiving preamplifier 110 is converted into a digital signal by an analog-to-digital converting A / D converter 120, where the CPU 150 receives the transmission from the transmission. The propagation time up to is measured. This requires measurement techniques for very short time periods (nanoseconds or picoseconds as needed) and the latest technology used in high-speed digital storage oscilloscopes. 14 and 15 show detailed circuit diagrams of the transmitting antenna 200 and the receiving antenna 300 according to the present invention.

In the present invention, a plurality of transmitting and receiving antennas (200, 300) using a plurality of transmission and reception antennas 200, 300 side by side evenly transmitted to the medium while passing through the target of one point quickly received pulses The echoes of will appear as multiple hyperbolas for space and time. In this case, it is judged that one target can be easily found by taking the vertices of several hyperbolas. If the echoes of these pulses are processed by a suitable algorithm and the continuous transmit / receive pulses are arranged, a visual effect close to 3D can be obtained. Therefore, it is possible to acquire information on the exact buried object.

Therefore, as described above, according to the antenna structure of the underground buried surface detector using the GPR system according to the present invention, the antenna resonance due to the reduction of the antenna resonance for the price effect by the use of the resistive termination device, the antenna directivity by adopting multiple reflectors It is possible to reduce the spread of unnecessary frequency by the proper use of the buffer material and to reduce the size and weight of the buffer material, and to use the multiple transmitting / receiving antennas to acquire more accurate information about the buried object. There is.

The present invention is not limited to the above-described specific preferred embodiments, and any person having ordinary skill in the art to which the present invention pertains may make various modifications without departing from the gist of the present invention claimed in the claims. Of course, such changes are intended to fall within the scope of the claims set forth.

Claims (3)

It controls the whole system, records and stores the signal transmitted from the receiving antenna 300, and transmits the data to the PC necessary for data processing indoors, the first time the signal is recorded in the control device 100 Determining various variables such as time, digital sampling interval of analog signal, total time range in which signal is recorded, stacking frequency, etc., and amplifying by generating transmit / receive pulse suitable for the determined variable. A control device (100) that radiates through the transmit antenna (200), amplifies and records the signal received through the receive antenna (300), and determines sampling intervals and the number and number of sampling intervals per trace; Transmitting and receiving antennas (200) (300) for radiating pulses generated by the control device (100) and receiving signals returned from the buried object after passing through the medium; A display unit 400 for implementing a pulse data obtained by the control apparatus 100 as an image, and displaying a cross-sectional view of a higher resolution by applying various implementation colors to a high-resolution screen for the processed data; Coaxial cable or optical cable is responsible for data transmission between the control device 100 and the transmitting and receiving antennas 200 and 300, and is responsible for transmitting the transmission of the radar wave and the reception of the reflected wave in the lowest noise state. Transmission line 900; And a power supply unit 500 for supplying driving power to each of the power units, using a DC power supply to reduce the generation of high-quality pulses and noise as the power required for the generation of electromagnetic pulses and transmission and reception of data. In the buried ground detection device, the transmitting antenna (200) uses a dipole antenna, the antenna structure of the underground buried ground detection device using a GPR system, characterized in that the antenna using a center frequency of approximately 200MHz. The method of claim 1, wherein a plurality of transmit and receive antennas (200, 300) are configured to transmit the same side by side from the antennas (200, 300) to the medium while quickly passing through the target of one point, the echo of the received pulse is space The antenna structure of the underground buried probe using the GPR system, characterized in that it appears as a number of hyperbolas with respect to time and to take the vertices of these hyperbolas to find one target. According to claim 1, Antenna structure of the underground buried surface detection device using a GPR system, characterized in that to further configure a resistive termination device to the transmitting and receiving antennas (200, 300).