CN1120990C - Underground imaging radar with impact pulses - Google Patents
Underground imaging radar with impact pulses Download PDFInfo
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- CN1120990C CN1120990C CN 00133082 CN00133082A CN1120990C CN 1120990 C CN1120990 C CN 1120990C CN 00133082 CN00133082 CN 00133082 CN 00133082 A CN00133082 A CN 00133082A CN 1120990 C CN1120990 C CN 1120990C
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Abstract
The present invention belongs to a wireless location and orientation technique, and relates to an imaging radar used for detecting earth surface structures and underground objects by a shock pulse. Under the synchronization of a system time base, the present invention emits a shock pulse signal to the underground; dispersion is generated in the boundary between an underground target and an underground medium; a dispersion echo signal enters into a receiving machine sampling system through an antenna; the dispersion echo signal is widened and changed into a low frequency signal on the basis of an original shape by time-domain sample exchange; then, imaging is displayed by proper processing. The present invention has the characteristics of high resolution, strong medium penetrating power, etc.
Description
The invention belongs to radiolocation and directional technology field, is a kind of imaging radar that utilizes shock pulse to survey surface infrastructure and underground object.
Thing is different with the detection of a target according to surveying, polytype radar system has appearred, as " airport surface detection radar (CN1190466A; open day 980812); " radar instrument for mine shaft geology " (CN1174998A; open day 980304), " a pulsed radar " (CN1173226A, open day 980211) etc. with scanning area valve.With regard to these radars, mainly comprise antenna, emission coefficient, receiving system and data handling system.Resemble CN1190466A and just comprise emitting antenna; Transmitter, it passes through the transmission antennas transmit CW signal of linear frequency modulation in fact; A monopulse receiving antenna and a monopulse receiver, it is by receiving antenna reception at least one response signal from a target on the ground, airport, produce orientation and signal and difference signal, and in response to instantaneous and and the direction of difference signal and antenna determine the position of target.
Underground imaging radar (GPR) is to survey under the face of land structure and bury the novel nondestructive detecting instrument of material underground, it utilizes the penetration capacity of electromagnetic wave to the face of land, launch the electromagnetic wave of certain form downwards from the face of land, electromagnetic wave produces scattering on the interface that characteristics of underground media changes, by receiving the scatter echo signal, time-delay according to echoed signal, parameter such as waveform and spectral characteristic, separate and translate target depth, dielectric structure and character, handle and digital imaging technology by computer data, underground target is carried out imaging processing, to reach the true of subsurface investigation target and to reproduce intuitively.
Underground radar has that speed of detection is fast, noncontact, non-destructive detections, resolution height, can directly obtain underground sectional view, the real time imagery that can carry out data is handled, economic advantages such as make things convenient for, have a wide range of applications, obtained the concern of some advanced country government departments and associated mechanisms, many countries have all dropped into lot of manpower and material resources and have carried out the development and the experimental work of underground radar.Though occurred some underground radar products in the last few years both at home and abroad successively, a lot of unsatisfactory places all arranged at aspects such as detection method, performance, precision, picture qualities.Thereby restricted the widespread use of underground radar.In addition, the underground radar equipment of import brings a high price, and has also limited its application.
Underground radar adopts following five kinds of technology to realize its function substantially both at home and abroad at present, and they are respectively: amplitude modulation(PAM) (Amplitude modulation); Continuous Wave with frequency modulation (FMCW); Continuous wave (Continuous wave); Pulse strenching-compress technique (also being the chirp radar) and polarization modulation (Polarization modulation).These five kinds of technical methods all have characteristics separately, also exist the complementarity in the application between some method.A cover is comparatively complete because the restriction of the complicated factors such as diversity of the scrambling of underground medium, the randomness of measured target and detection method, underground radar also do not form, detection theory and technology ripe, system.
The purpose of this invention is to provide a kind of employing shock pulse as transmitting, survey the underground imaging radar of structure and underground thing under the face of land, the resolution of the detection of a target and aspects such as different medium penetration capacity are had special advantages.
Underground radar is to come from the airborne radar development of routine, and its basic theories and technical foundation also come from airborne radar.Underground radar will detect is back scattering from buried target.
The present invention is that base is down synchronous when system, radar transmitter is that 5ns crest voltage be ± 160V pulse signal by emitting antenna to underground emission pulsewidth with the frequency of 100KHz, when running into buried target, it will produce scattering at the boundary of target and underground medium, the scatter echo signal enters the receiver sampling system through receiving antenna, by time domain sampling conversion, make echoed signal on the basis that keeps original shape on time shaft broadening 2000 times and become low frequency signal.Send into the underground sectional view that Flame Image Process and image display system form search coverage after this signal suitably handled.
Fig. 1 is a theory diagram of the present invention.It is antenna part, radiating portion, receiving unit, data pre-service and display part, computing machine sequential control part that the present invention is divided into five parts.Wherein, antenna is the knot type element antenna that sending and receiving separate, and antenna has the wideband impedance match characteristic; Transmitter is after trigger pulse arrives, and the avalanche characteristic by avalanche transistor produces pulse width, and to be 5ns, amplitude be the double direction impulse pulse of ± 160V, and pulse repetition rate is 100KHz; Receiver section comprises sampling pulse generator, sampling gate, amplification, broadening and amplitude gain control circuit, and the echoed signal that receives is transformed into easy-to-handle slow signal, and the noise figure of receiver is 6dB; Sequential control part by mainly shake, fast ramp generator, slow ramp generator, comparer etc. form, it except emission be provided for transmitter and receiver trigger and sample trigger, also to provide look-at-me for the data pre-service; 12 high-speed a/d transducers are adopted in data processing and display part, and precision is 5mV; It sends into image display after the data that receive are handled in real time, shows 16 look false color images in real time.
Fig. 2 is that each several part of the present invention connects demonstration overall plan block diagram.
Fig. 3 is a signal timing diagram of the present invention.(A) (B) is the comparison procedure waveform for the master of the geodetic radar system waveform that shakes among the figure, (C) is emission trigger pip waveform, (D) be through the relatively sampling pulse trigger pip of generation of too fast oblique wave with slow oblique wave, (E) is echo waveform, (F) is the broadening waveform.
In signal timing diagram shown in Figure 3, the time reference of system is provided by the 100KHz crystal oscillator of a high stability, and the degree of stability of crystal oscillator is 10
-5Because the range finding of underground radar belongs to in-plant range finding, echo only is the ns magnitude apart from the exomonental time, if adopt the public antenna system of transmitting-receiving, the switch speed of ns level has certain technical difficulty to radio-frequency (RF) switch.Consider to have adopted the dual-mode antenna separation mode from engineering.By the trigger pip that relatively produce sampling pulse of fast oblique wave with slow oblique wave, cycle is T+ Δ t, when the sample-pulse signal of transponder pulse and certain one-period is synchronous, sampling pulse is at previous relatively transponder pulse of each cycle thereafter Δ t of multiple-time delay all, n cycle, delaying time is n * Δ t, when sampling pulse arrives, sampling gate is opened, and the time of opening the door equals sampling pulse width τ.Each time clock will obtain a sampling point of echo waveform like this, and these sampling points are integrated in amplification and widening circuit, through a slow oblique wave cycle, form a new broadened in time echo waveform, shown in (F) among Fig. 3.The shape of sample envelope is consistent with echo waveform, but the duration increased thousands of times, example of the present invention is 2000 times.Then the echoed signal behind the broadening is carried out the A/D conversion and send into image processing section, the imaging of after Flame Image Process and software processes, on display, rolling in real time.
Antenna part of the present invention comprises receiving antenna and emitting antenna, and receiving antenna and emitting antenna separate, and is independently of one another.Radiating portion comprises transponder pulse controller and transmitter.Receiving unit comprises the sampling pulse controller, the sampling pulse generator, and sampling gate amplifies widening circuit, amplitude control circuit and low wave filter.Data pre-service and display part comprise A/D converter, main control computer and display.The computing machine sequential control partly comprises the main 100KHz that shakes, fast ramp generator, slow ramp generator and two comparers.The signal of the main 100KHz that shakes is divided into two-way, and one the tunnel enters fast ramp generator, and another road enters slow ramp generator, and fast ramp generator is connected with 2 with comparer 1 respectively, and slow ramp generator is connected with comparer 2.The signal choosing that comparer 1 comes out enters the transponder pulse controller, then sends the shock pulse signal to transmitter by emitting antenna.The signal that comparer 2 comes out then enters the sampling pulse generator earlier through the sampling pulse controller, arrives sampling gate at last.After the receiving antenna received signal,, enter into and amplify and unfolding circuits, enter into amplitude control circuit then, behind low-pass filter, enter main control computer by the A/D conversion earlier through sampling gate.Between slow ramp generator and the main control computer is interconnective.
The shock pulse of the present invention's emission requires antenna to have very wide bandwidth.Because the transponder pulse of native system is that repetition frequency is that 100KHz, pulsewidth are the shock pulse of 5ns, therefore require emitting antenna that the bandwidth of 100KHz～200MHz is arranged.So wide relative bandwidth makes antenna need emphasis to consider impedance bandwidth in design and test process, and all oscillator form antennas all belong to the arrowband resonant antenna, be difficult to reach the desired performance of system, so native system has adopted knot type a period of time antenna of top resistance loading.Fig. 4 is knot type a period of time antenna synoptic diagram of the present invention.
The thick copper coin of 1mm that knot emitting antenna shown in Figure 4 is arranged relatively by the collar point of two identical knot structures constitutes, the length of each knot is 500mm, the width of knot broadside and between the upper and lower distance be respectively 100mm, between two sheet metals of broadside and to be connected to ten resistances be the identical pull-up resistors of 820 Ω, to improve bandwidth performance, two knot spacings are 25mm, and the resistance that top adds 75 Ω shields.
Transmitter of the present invention mainly is to utilize the avalanche effect characteristic of triode when high pressure uses to produce burst pulse significantly, when transistorized collector voltage is enough high, the normal low pressure of electric field ratio of collecting in the knot space charge region is used big manyfold, entering the charge carrier of collecting knot is quickened by highfield, thereby obtain very macro-energy, just produced new electron hole when they and lattice collisions.New electronics, the hole that produces quickened by highfield respectively again and repeated said process.So flow through just " snowslide " formula growth of electric current of collecting knot, transistorized avalanche multiplication phenomenon that Here it is.
Based on above-mentioned principle the present invention adopted Chinese Academy of Sciences Changchun geographical " underground detection radar transmitter " (CN2289250Y, the day for announcing 980826) circuit of patent, having made repetition frequency is 100KHz, and pulsewidth is 5ns, and amplitude is ± the 160V shock pulse.Fig. 5 is the shock pulse oscillogram.
Receiving unit of the present invention mainly is made up of sampling pulse generator, sampling gate, amplification widening circuit, amplitude control circuit and low-pass filter.Adopt the sampling converter technique that the echoed signal that receives is transformed into easy-to-handle slow signal.Native system is taken a sample with stepping, as shown in Figure 3, with the sample stepping in each cycle Δ t, and the Δ t in each cycle equates.The process of sampling conversion is a process of accumulation synchronously, has therefore improved signal to noise ratio (S/N ratio) greatly.
Therefore the key property of the shape of sampling pulse decision sampling system requires the sampling pulse generator that the sample trigger shaping pulse is become the pulse of high speed step response, by differentiating circuit, makes step pulse form enough narrow spike pulse then.Sampling pulse generator circuit as shown in Figure 6.
By selecting element and parameter, debug results is: the sampling amplitude is 3V; Bottom width is 2ns; The bias voltage of positive negative pulse stuffing is respectively+2V and-2V.
Sampling gate is the circuit that takes out sample, and generally, sampling gate is closed, and sampling gate is opened when sampling pulse arrives, and signal is taken a sample.The frequency characteristic of sampling gate and excessive characteristic are except the frequency characteristic that depends on sampling pulse and sampling gate structure, and be also relevant with the selected diode switch speed of sampling gate.In order to reduce the distorted signals of sampling process as far as possible, the sampling diode must be the speed-sensitive switch diode.
Sampling gate of the present invention can be selected four pipe symmetric sampling gates, circuit as shown in Figure 7, among the figure ± Ep is a bias voltage.
We know that sampling pulse is narrow more, and the bandwidth of sampling system is wide more.In order to cooperate the emission pulsewidth of 5ns, the bandwidth of sampling system is greater than 200MHz, and the sampling pulse bottom width is less than 3ns, so the present invention has selected for use homemade 2KE64B as the sampling diode.
Amplify widening circuit, amplitude gain control circuit and low-pass filter have been formed low frequency of the present invention processing section.Low frequency is handled block diagram as shown in Figure 8.
In amplifying widening circuit, the present invention has adopted field effect transistor low noise integrating amplifier to realize the broadening of underground echoed signal.The discrete sample point that is sampling gate output is through having reappeared the envelope of signal behind the integrating amplifier, as the broadening waveform among Fig. 3 (F).
The echo signal amplitude of underground radar has very big variation range.This is owing to the direct wave from the face of land makes the section start signal amplitude very big, adds because underground decay causes the increase signal amplitude with echo delay time more and more littler.This amplitude scope over time can reach 40dB sometimes, thereby the start-up portion that makes echoed signal is easy to produce saturated phenomenon when amplifying, so, the present invention has adopted overload-resistant amplitude gain control circuit, it is saturated that the strong face of land echo of amplitude is not amplified to, and can obtain higher gain from the weak signal of buried target.
In data pre-service and display part, the present invention has adopted the Interface design of isa bus, and data processing is as computer interface circuits, by isa bus realize with computing machine between communicate by letter and control.
The data processing block diagram as shown in Figure 9.
Data processing is made up of single-chip microcomputer, Intel8254 timing controller and programmable gain amplifier etc.Single-chip microcomputer gives processing by the Intel8254 control data and image shows and the synchronous operation of image processing software.The control of single-chip microcomputer realizes that by the Intel8254 timer (1MHz 10MHz) forms with three programmable counters timer by two high precision crystal oscillators.Wherein connect the cycle trigger end of A/D trigger after two counter cascades.The voltage amplification factor of programmable gain amplifier is 0～255, can reach the voltage gain scope of 48dB, and the AGC signal of controlling it is produced by computer software.Be 3 μ s high-speed a/d transducer switching time of adopting, and in conjunction with the first in first out data stack of 1K byte, the rapid rate of data transmission is 330KHz.The resolution of A/D conversion is 12, input voltage range ± 10V, and precision is less than 5mV.Data transmission adopts interrupt mode, synchronizing pulse with slow oblique wave when being the echo arrival interrupts to the CPU of computing machine application by isa bus, notice computing machine echo this moment arrives, carrying out the A/D conversion, the single-chip microcomputer that gives the processing section in data is directly under the jurisdiction of data converted to pass to host CPU with the speed of 330KHz, is handled by the interrupt service routine of software.The design of the FIFO stack of 1K byte is loss of data to occur for fear of the data with the A/D conversion when carrying out high-speed transfer by bus.The output of A/D at first enters storehouse, and reading of data from storehouse even there is more senior interruption to take place like this, loss of data can not take place yet.
The system environments of software is DOS6.22, and CPU is the Pentium chip of 133MHz, and interruptable controller is the Inel8259 of master-slave mode, in save as 32MB.
Software is divided into interface program, initialize routine, interrupt service routine, data processor and image display program.All programs adopt C language compilation basically, and nested part assembly routine improves program implementation speed so that reduce program code in interrupt handling routine, data processor and image display program.
VGA color graphics menu has been adopted at the interface, attractive in appearance, the easy operating of man-machine dialog interface.
Initialize routine is used for the setting program parameter, setting program gives parameter of processing section etc.
No. 12 of adopting computing machine to keep of break in service are interrupted, and rising edge triggers, and are used for synchronizing software and data to give data communication between processing.
Data processor also will be realized the real-time deposit and the readjustment of data except that the data after the A/D conversion are carried out the various real-time processing.Image display program can be realized 16 looks, 640 * 480 pixel real time data rolling imaging processing.In order to improve speed of displaying, this program is directly operated the display buffer internal storage, can realize that per second is higher than the image refreshing speed of 50Hz.
The present invention adopts shock pulse as transmitting, and it is high and to characteristics such as the medium penetration capacity are strong to have detection of a target resolution.
Claims (9)
1, a kind of underground imaging radar with impact pulses, mainly by antenna, radiating portion, receiving unit, data pre-service and the display part composition that grades, transmitter in the radiating portion is with the pulse signal of certain frequency by day certain pulsewidth degree of the underground emission of alignment and peak power, this pulse signal runs into buried target and produces scattering, scatter echo enters receiving unit through antenna, through data pre-service and display part, form the buried target profile image, feature of the present invention is that base is down synchronous when system, transmitter is that 5ns crest voltage be ± 160V pulse signal by emitting antenna to underground emission pulsewidth with the frequency of 100KHz, border at target and underground medium when this pulse signal runs into buried target produces scattering, and the scatter echo signal enters the receiver sampling system through receiving antenna; Receiving unit passes through the sampling pulse controller, the sampling pulse generator, and sampling gate amplifies widening circuit, and amplitude control circuit and low-pass filter are transformed into easy-to-handle slow signal with the echoed signal that receives; By time domain sampling conversion, make echoed signal on the basis that keeps original shape on time shaft 2000 times of broadenings and become low frequency signal, send into Flame Image Process and image display system after this low frequency signal is suitably handled, imaging demonstrates buried target.
2, underground imaging radar with impact pulses according to claim 1 is characterized in that antenna is the knot type element antenna that sending and receiving separate, and has the wideband impedance match characteristic, and gaining is 3dB; Data are given and being handled and the display part comprises A/D converter, and main control computer and display are sent into image display after the data of reception are handled in real time, show 16 look false color images in real time; The computing machine sequential control partly comprises the main 100KHz that shakes, fast ramp generator, and slow ramp generator and two comparers, this part is also wanted coordination data to handle look-at-me is provided except emission triggering and sample trigger are provided for transmitter and receiver.
3, underground imaging radar with impact pulses according to claim 2, the signal that it is characterized in that the main 100KHz that shakes is divided into two-way, one the tunnel enters fast ramp generator, another road enters slow ramp generator, fast ramp generator is connected with 2 with comparer 1 respectively, and slow ramp generator is connected with comparer 2; The signal that comparer 1 comes out is introduced into the transponder pulse controller, then arrives transmitter, sends the shock pulse signal by emitting antenna; The signal that comparer 2 comes out then enters the sampling pulse generator earlier through the sampling pulse controller, arrives sampling gate at last; After receiving a day received signal,, enter into and amplify and unfolding circuits, enter into amplitude control circuit then, behind low-pass filter, enter main control computer by the A/D conversion earlier through sampling gate; Between slow ramp generator and the main control computer is interconnective.
4, underground imaging radar with impact pulses according to claim 3 is characterized in that adopting the sampling converter technique that the echoed signal that receives is transformed into easy-to-handle slow signal, each cycle sample has been carried out Δ t, and the Δ t in each cycle equates.
5, underground imaging radar with impact pulses according to claim 3 is characterized in that the sampling pulse generator becomes the high speed step response pulses with the sample trigger shaping pulse, by differentiating circuit, makes step pulse form enough narrow spike pulse then.
6, underground imaging radar with impact pulses according to claim 3, the taking-up sample circuit that it is characterized in that sampling gate are four pipe symmetric sampling gates, and the sampling diode is the speed-sensitive switch diode.
7, underground imaging radar with impact pulses according to claim 3, it is characterized in that in data pre-service and display part, adopt the isa bus Interface design, data processing is as the computer interface circuit, by isa bus realize with computing machine between communicate by letter and control.
8, underground imaging radar with impact pulses according to claim 7 is characterized in that data processing is made up of single-chip microcomputer, Intel8254 timing controller and programmable gain amplifier etc.Single-chip microcomputer gives processing by the Intel8254 control data and image shows and the synchronous operation of image processing software.
9, underground imaging radar with impact pulses according to claim 8, the system environments that it is characterized in that software is DOS6.22, CPU is the Pentium chip of 133MHz, interruptable controller is the Intel8259 of master-slave mode, in save as 32MB; Software is divided into interface program, initialize routine, continuous service routine, data processor and image display program; Master routine adopts C language compilation basically, nested part assembly routine in interrupt handling routine, data processor and image display program.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| US20230099685A1 (en) * | 2020-03-02 | 2023-03-30 | Calterah Semiconductor Technology (Shanghai) Co., Ltd. | Automatic gain control method, sensor, and radio device |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| AU2002368401A1 (en) * | 2002-12-02 | 2004-06-23 | Nokia Corporation | Determination of the position of a pulse peak |
| CN100368822C (en) * | 2005-12-05 | 2008-02-13 | 国家无线电监测中心 | Radio emitting source positioning method and system |
| CN102508305A (en) * | 2011-09-29 | 2012-06-20 | 无锡军帅电子科技有限公司 | Ultra wide band radar life detection system and method |
| CN102590875B (en) * | 2012-03-01 | 2013-12-18 | 赤峰宏远地质勘查有限公司唐山迁西分公司 | Remote sensing geophysical exploration system and remote sensing geophysical exploration method |
| CN107290744B (en) * | 2016-04-11 | 2023-04-25 | 中国水利水电科学研究院 | Ice thickness water depth comprehensive detection radar system and method |
| CN111665570B (en) * | 2020-05-26 | 2023-04-25 | 广西电网有限责任公司南宁供电局 | Underground cable pipeline imaging detection method and device based on 3D ground penetrating radar |
| CN111764442B (en) * | 2020-06-04 | 2021-12-17 | 济南轨道交通集团工程研究咨询有限公司 | Method for predicting water leakage at joint of underground diaphragm wall of foundation pit |
| CN112781447B (en) * | 2021-01-20 | 2023-09-01 | 湖南科技大学 | Land mine detection device based on UWB pulse electromagnetic wave |
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| US20230099685A1 (en) * | 2020-03-02 | 2023-03-30 | Calterah Semiconductor Technology (Shanghai) Co., Ltd. | Automatic gain control method, sensor, and radio device |
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