CN113805172A - Equivalent sampling method and system for ground penetrating radar with time-varying gain - Google Patents
Equivalent sampling method and system for ground penetrating radar with time-varying gain Download PDFInfo
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
- G01S13/88—Radar or analogous systems specially adapted for specific applications
- G01S13/885—Radar or analogous systems specially adapted for specific applications for ground probing
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
- G01S7/28—Details of pulse systems
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- G01S7/292—Extracting wanted echo-signals
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Abstract
The invention provides a ground penetrating radar equivalent sampling method and system with time varying gain, wherein a square wave signal of a radar is divided into two paths, one path is used for triggering a narrow pulse signal source to generate periodic narrow pulses, the other path of the square wave signal triggers a sampling circuit after time delay, the time delay ending time is used as sampling time, and the sampling circuit acquires a time varying gain radar echo signal of each period of the sampling time by an equivalent sampling method. Through adding the time-varying gain for radar echo signal to amplify the signal before the signal gets into the ADC chip, avoided digital gain to the adverse effect that quantization noise amplification caused, also can amplify the echo signal of the deeper target in underground simultaneously, make echo signal more clear, solve the problem of radar echo signal decay with time, through the radar echo of amplifying the reflection of the deeper target in underground, improve radar detection degree of depth and precision, thereby promote the detectivity of radar by a wide margin.
Description
Technical Field
The invention belongs to the technical field of radars, and particularly relates to a ground penetrating radar equivalent sampling method and system with time-varying gain.
Background
The ground penetrating radar technology is used as a nondestructive underground target detection technology and plays an extremely important and extensive role in the aspects of military investigation, mineral geological exploration, engineering quality inspection, archaeology, search and rescue and the like. The common ground penetrating radar mainly comprises a main control circuit, a narrow pulse signal source, a transmitting-receiving antenna and an upper computer 4. The performance of a sampling circuit of the main control circuit part directly influences the detection depth and the detection precision of the radar. The bandwidth of a typical narrow pulse signal of the ground penetrating radar is more than 500MHz, a sampling rate of more than 4GSPS is needed to sample the narrow pulse signal in actual engineering, a high requirement is provided for the real-time sampling rate of a sampling circuit, and although a small number of high-speed ADC chips meeting the real-time sampling requirement exist in the market, the narrow pulse signal is difficult to be widely applied due to the reasons of high price, low sampling precision, difficult software and hardware development and the like.
Equivalent sampling is based on approximate periodicity of radar echo signals, a control unit of a radar main control circuit generates a square wave signal and divides the square wave signal into two branches, one branch is used for triggering a narrow pulse signal source, and the other branch obtains an ADC trigger clock with step delay through a delay circuit, so that a very high equivalent sampling rate can be obtained by using a low sampling rate ADC chip, the performance of the ground penetrating radar is improved, and the production cost of the ground penetrating radar is reduced.
However, the radar echo signal also has the characteristic of attenuation along with time, namely, the radar echo returned by a target deeper in the ground is more attenuated along with the time, so that the detection depth and the detection accuracy of the radar are limited. Although the ordinary equivalent sampling can realize the high sampling rate of the ground penetrating radar, the improvement on the detection depth and the accuracy of the radar is limited. Although the upper computer in the radar system can provide digital gain for the radar echo signal to amplify the tiny echo signal, noise in the signal is also amplified synchronously at this time, and especially quantization noise exists in ADC chip sampling, so that the amplification provided by the digital gain has a limited effect on the analysis and processing of the signal.
Disclosure of Invention
Aiming at the problems in the prior art, the invention aims to provide a ground penetrating radar equivalent sampling method and system with time-varying gain, which solve the problem that a radar echo signal decays along with time, so as to improve the detection performance of the existing ground penetrating radar.
The invention is realized by the following technical scheme:
the equivalent sampling method of the ground penetrating radar with the time-varying gain comprises the steps of dividing a square wave signal of the radar into two paths, wherein one path of the square wave signal is used for triggering a narrow pulse signal source to generate periodic narrow pulses, the other path of the square wave signal triggers a sampling circuit after time delay, the time delay ending time is used as sampling time, and the sampling circuit obtains a time-varying gain radar echo signal of each period of the sampling time by an equivalent sampling method.
Preferably, the time duration of the delay in the sampling process is increased with the sampling period.
Preferably, the pulse signal is input to the delay circuit to generate a delayed square wave signal to trigger the sampling circuit.
Preferably, the frequency of the square wave signal is matched with the trigger frequency of the narrow pulse signal source.
A system of a ground penetrating radar equivalent sampling method with time-varying gain comprises a control unit, a narrow pulse signal source, a delay circuit, an ADC sampling circuit and a conditioning circuit, wherein the narrow pulse signal source, the delay circuit, the ADC sampling circuit and the conditioning circuit are connected with the control unit;
the control unit is used for generating stable square wave signals and respectively sending the square wave signals to the narrow pulse signal source and the delay circuit;
the narrow pulse signal source is used for generating periodic pulse signals according to the square wave signals;
the delay circuit is used for delaying the received square wave signal and then sending the delayed square wave signal to the ADC sampling circuit;
the conditioning circuit is used for applying time-varying gain to the radar echo signal;
the ADC sampling circuit is used for acquiring a gain radar echo signal by an equivalent method.
Preferably, the periodic pulse signal is sent through a transmitting antenna, a receiving antenna transmits a radar echo signal to a conditioning circuit, and the transmitting antenna and the receiving antenna are matched with the center frequency and the bandwidth of the narrow pulse signal source.
Preferably, the conditioning circuit comprises a cascade of a fixed power amplifier and a programmable gain operational amplifier;
the fixed power amplifier has a fixed gain and is used for providing a basic gain for a radar echo signal; the programmable gain operational amplifier has a certain programmable gain range and is used for providing time-varying gain for the radar echo signal.
Preferably, the delay circuit is a programmable delay chip or a plurality of cascaded delay chips.
Preferably, the stepping delay value of the delay circuit is less than 4 times of the reciprocal of the bandwidth of the pulse signal, the maximum delay value is set to be not less than the period of a single effective radar echo signal, and the radar system is enabled to receive radar echo information.
Compared with the prior art, the invention has the following beneficial technical effects:
the invention provides a ground penetrating radar equivalent sampling method with time-varying gain, which divides a square wave signal of a radar into two paths, wherein one path of the square wave signal is used for triggering a narrow pulse signal source to generate periodic narrow pulses, the other path of the square wave signal triggers a sampling circuit after time delay, the time delay ending time is taken as sampling time, and the sampling circuit acquires a time-varying gain radar echo signal of each period of the sampling time by an equivalent sampling method. Through adding the time-varying gain for radar echo signal to amplify the signal before the signal gets into the ADC chip, avoided digital gain to the adverse effect that quantization noise amplification caused, also can amplify the echo signal of the deeper target in underground simultaneously, make echo signal more clear, solve the problem of radar echo signal decay with time, through the radar echo of amplifying the reflection of the deeper target in underground, improve radar detection degree of depth and precision, thereby promote the detectivity of radar by a wide margin.
Furthermore, a conditioning circuit formed by cascading a fixed gain power amplifier and a programmable gain operational amplifier is convenient for adjusting the basic gain of an input signal, so that the amplitude of a radar echo signal can be flexibly adjusted to adapt to the amplitude range of the input signal of an ADC chip, the requirement of signal processing on the digital gain of an upper computer is reduced, the signal-to-noise ratio of the processed signal is improved, and the software processing difficulty is reduced.
Furthermore, the radar control unit can provide time-varying gain for radar echo through controlling the programmable operational gain amplifier in real time, amplify the radar echo reflected by a target in an underground depth, and improve the detection depth and precision of the radar.
Drawings
Fig. 1 is a schematic diagram of time-varying gain equivalent sampling according to the present invention.
In the figure: 1. a radar echo signal; 2. a square wave signal edge; 3. a logarithmic gain; 4, restored radar echo signals; t1 is radar echo period; t2 is the time interval between two adjacent samples; t1 is the step delay of two adjacent samples.
Detailed Description
The present invention will now be described in further detail with reference to the attached drawings, which are illustrative, but not limiting, of the present invention.
Referring to fig. 1, a ground penetrating radar equivalent sampling method with time-varying gain divides a square wave signal generated by a radar control unit into two paths, one path is used for triggering a narrow pulse signal source to generate periodic narrow pulses, the other path is delayed to trigger an ADC sampling circuit, the delay ending time is used as a sampling time, and the ADC sampling circuit acquires a gain radar echo signal of the sampling time;
and repeating the process until the radar echo signal at each period sampling time in the sampling interval is obtained, wherein the delay time in the sampling process is increased along with the sampling period.
The radar control unit generates a stable square wave signal, the frequency of the square wave signal is matched with the trigger frequency of the narrow pulse signal source, and the narrow pulse signal source is periodically triggered through the square wave signal to generate a periodic pulse signal; and the other path of square wave signal is input to a delay circuit, and the delay circuit generates a delay square wave signal to trigger an ADC sampling circuit to acquire radar echo signals.
In the acquisition process, radar echo signals are regulated and controlled by a conditioning circuit and then input to an ADC (analog to digital converter) sampling circuit, the conditioning circuit enables the radar echo signals to obtain time-varying gain, and an ADC chip obtains the gain radar echo signals at each period of sampling time by adopting an equivalent sampling method.
A ground penetrating radar equivalent sampling system with time varying gain comprises a control unit, and a narrow pulse signal source, a delay circuit, an ADC sampling circuit and a conditioning circuit which are connected with the control unit.
The control unit is used for generating stable square wave signals and respectively sending the square wave signals to the narrow pulse signal source and the delay circuit.
The square wave signal triggers a narrow pulse signal source to generate a periodic pulse signal and transmits the periodic pulse signal to a transmitting antenna for transmitting; and sending the delayed square wave signal to an ADC sampling circuit, and triggering the ADC sampling circuit to sample.
The receiving antenna transmits the radar echo signals to the conditioning circuit, the conditioning circuit applies time-varying gain to the radar echo signals, and the ADC sampling circuit obtains the time-varying gain radar echo signals at each period of sampling time by an equivalent sampling method.
The transmitting antenna and the receiving antenna are matched with the center frequency and the bandwidth of the narrow pulse signal source.
The conditioning circuit is formed by cascading a fixed power amplifier and a programmable gain operational amplifier, wherein the fixed power amplifier has a fixed gain and is used for providing a basic gain for a radar echo signal; the programmable gain operational amplifier has a certain programmable gain range and is used for providing time-varying gain for the radar echo signal, and the radar control unit controls the conditioning circuit to add gain which increases gradually along with time to the radar echo signal to compensate signal attenuation caused by underground transmission, so that the time-varying gain of the radar echo signal is realized.
The delay circuit comprises a programmable delay chip or a plurality of cascaded delay chips; according to the Nyquist sampling law and the actual engineering requirements, the stepping delay value of the delay circuit is set to ensure that the equivalent sampling rate is more than 8 times of the bandwidth of the pulse signal; the observation time window for receiving the pulse signal is equal to a set maximum delay value, the maximum delay value is related to a set stepping delay value and the number of sampling points, and not only the maximum delay value is far smaller than a square wave signal period value for triggering a narrow pulse signal source, but also the radar system is ensured to be capable of receiving enough radar echo information.
According to the time-varying gain equivalent sampling implementation principle of the invention, as shown in fig. 1, an ADC sampling chip of a radar main control circuit receives a radar echo signal 1 of an approximate period, and performs sampling under the trigger of a square wave signal edge 2. The square wave signal edge 2 is generated synchronously with the square wave signal triggering the narrow pulse signal source and lags behind the square wave signal triggering the narrow pulse signal source for a period of time through a programmable delay circuit. The period of time is determined by a delay value set by a programmable delay circuit, and is increased by taking T1 as a stepping value and T1 as a period value under the coordination of a control unit, and the delay value is cleared and is increased in a circulating mode again when reaching a set maximum value. In the sampling process, the main control unit controls the programmable gain operational amplifier at intervals, modifies the logarithmic gain 3 of the programmable gain operational amplifier, makes the logarithmic gain value increase linearly along with time, and returns to the initial value when the delay value is 0. The radar echo signal 4 obtained through equivalent sampling recovery is stretched in time relative to the input radar echo signal 1, and a small-amplitude signal at the tail end of the input echo signal 1 is obviously amplified, so that the detection of a target in the deep underground is facilitated.
The equivalent sampling method of the ground penetrating radar with the time-varying gain comprises the steps that two clocks which trigger a narrow pulse signal source and an ADC (analog-to-digital converter) sampling chip are generated by a radar control unit, the programmable delay circuit and the programmable signal conditioning circuit are controlled, equivalent sampling and the time-varying gain are respectively realized, the equivalent sampling process with the time-varying gain is finally realized, the time-varying gain is added to a radar echo signal, the signal is amplified before the signal enters the ADC chip, the adverse effect of digital gain on quantization noise amplification is avoided, meanwhile, the echo signal of a target in a deeper underground position can be amplified, the problem that the radar echo signal is attenuated along with time is solved, the echo signal is clearer, the radar echo reflected by the underground target in the deep position is amplified, the detection depth and the detection precision of the radar are improved, and the detection performance of the radar is greatly improved.
The above-mentioned contents are only for illustrating the technical idea of the present invention, and the protection scope of the present invention is not limited thereby, and any modification made on the basis of the technical idea of the present invention falls within the protection scope of the claims of the present invention.
Claims (9)
1. The equivalent sampling method for the ground penetrating radar with the time-varying gain is characterized in that a square wave signal of the radar is divided into two paths, one path of the square wave signal is used for triggering a narrow pulse signal source to generate periodic narrow pulses, the other path of the square wave signal triggers a sampling circuit after time delay, the time delay ending time is used as sampling time, and the sampling circuit obtains a time-varying gain radar echo signal of each period of the sampling time by an equivalent sampling method.
2. The equivalent sampling method of the ground penetrating radar with the time varying gain as recited in claim 1, wherein the time delay duration in the sampling process is increased with the sampling period.
3. The equivalent sampling method of the ground penetrating radar with the time varying gain as claimed in claim 1, wherein the pulse signal is input to the delay circuit to generate a delayed square wave signal to trigger the sampling circuit.
4. The method for equivalently sampling the ground penetrating radar with the time-varying gain according to claim 1, wherein the frequency of the square wave signal is matched with the trigger frequency of the narrow pulse signal source.
5. The system of the equivalent sampling method of the ground penetrating radar with the time-varying gain is characterized by comprising a control unit, and a narrow pulse signal source, a delay circuit, an ADC sampling circuit and a conditioning circuit which are connected with the control unit;
the control unit is used for generating stable square wave signals and respectively sending the square wave signals to the narrow pulse signal source and the delay circuit;
the narrow pulse signal source is used for generating periodic pulse signals according to the square wave signals;
the delay circuit is used for delaying the received square wave signal and then sending the delayed square wave signal to the ADC sampling circuit;
the conditioning circuit is used for applying time-varying gain to the radar echo signal;
the ADC sampling circuit is used for acquiring a gain radar echo signal by an equivalent method.
6. The system of equivalent sampling method for ground penetrating radar with time varying gain as claimed in claim 5, wherein said periodic pulse signal is transmitted through a transmitting antenna, a receiving antenna delivers radar echo signal to a conditioning circuit, and said transmitting antenna and receiving antenna are matched with the center frequency and bandwidth of the narrow pulse signal source.
7. The system of equivalent sampling method for ground penetrating radar with time varying gain as claimed in claim 5, wherein said conditioning circuit comprises a cascade of fixed power amplifier and programmable gain operational amplifier;
the fixed power amplifier has a fixed gain and is used for providing a basic gain for a radar echo signal; the programmable gain operational amplifier has a certain programmable gain range and is used for providing time-varying gain for the radar echo signal.
8. The system of the equivalent sampling method of the ground penetrating radar with the time varying gain according to claim 5, wherein the delay circuit is a programmable delay chip or a plurality of cascaded delay chips.
9. The system of equivalent sampling method for ground penetrating radar with time varying gain as set forth in claim 6, wherein the step delay value of said delay circuit is less than 4 times of the reciprocal of the pulse signal bandwidth, the maximum delay value is set to be not less than the period of a single valid radar return signal, and the radar system is enabled to receive radar return information.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN117784123A (en) * | 2023-11-15 | 2024-03-29 | 北京市燃气集团有限责任公司 | Method and system for acquiring deeper underground medium data |
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