CN1564024A - Width realtive processing method of super broadband ground finding radar based on time frequency analysis - Google Patents

Width realtive processing method of super broadband ground finding radar based on time frequency analysis Download PDF

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CN1564024A
CN1564024A CN 200410017540 CN200410017540A CN1564024A CN 1564024 A CN1564024 A CN 1564024A CN 200410017540 CN200410017540 CN 200410017540 CN 200410017540 A CN200410017540 A CN 200410017540A CN 1564024 A CN1564024 A CN 1564024A
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frequency
instantaneous
signal
echo
centre frequency
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CN1259629C (en
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李建勋
肖艳军
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Shanghai Jiaotong University
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Abstract

First, temporal frequency is carried out for return signal. Further, instantaneous parameters: instantaneous center frequency, bandwidth and main frequency representing non-stationary signal characteristics are obtained. Frequency filter is completed by using instantaneous center frequency, and instantaneous bandwidth to reduce interference on target signal caused by multiple reflection echo, making wide matching relation be formed between return signal and transmitted master wave from radar. Stretching factor is evaluated and matching master wave is built by using instantaneous center frequency and master wave, so that optimization problem in dual parameters is converted to one parameter time delay estimation problem of matched filtering. Thus, target signal in optimal time delay estimation and enhanced return signal are obtained. The invention possesses important meaning and use value for practical application system, especially for handset.

Description

Based on the wide correlation process method of the ultra-wideband ground-penetrating radar (uw-gpr) of time frequency analysis
Technical field
The present invention relates to the wide correlation process method of a kind of ultra-wideband ground-penetrating radar (uw-gpr) based on time frequency analysis, be the implementation method of a through engineering approaches in the ground penetrating radar signal Processing field, survey at underground metal and nonmetal pipeline, all be widely used in national security such as location, archaeological site, geologic section exploration, highway quality check and safety inspection and the economic field.
Background technology
Ground penetrating radar is utilized electromagnetic wave detection buried target (as cavity, pipeline, land mine etc.), by analyzing the interaction of electromagnetic signal and buried target, information such as the character of extraction target, shape.Actual at present ground penetrating radar system transmits and all adopts the no carrier frequency base band pulse of several nanoseconds of pulsewidth, and its effective spectrum scope reaches several GHz from tens MHz approximately, belongs to the ULTRA-WIDEBAND RADAR system.Ultra-wideband ground-penetrating radar (uw-gpr) can obtain higher spatial and temporal resolution because frequency spectrum medium-high frequency content is abundant, and underground medium structure, buried target are surveyed, located and discern, and underground target and dielectric structure are carried out imaging.
In view of the characteristics of ultra broadband echoed signal, classical signal processing method can not solve problems such as the target detection of ultra-wideband ground-penetrating radar (uw-gpr) and identification effectively.Present ultra-wideband ground-penetrating radar (uw-gpr) signal processing method mainly is to be based upon on the wide relevant treatment basis, the method that realizes comprises: continuous wavelet transform (T.Le-Tien, H.Talhami and D.T.Nguyen, " Target Signature Extraction Based on the ContinuousWavelet Transform in Ultra-Wideband Radar; " IEE Electronics Letters, Vol.33, Issue1, January 1997) and multiparameter direct estimation (Zhan Yi, the horse Long March, Liang Changhong, Fang Guangyou, the parameter estimation problem of broadband coherent signal, Xian Electronics Science and Technology University's journal, 26 (4), pp467-470,1999).Yet change for continuous wavelet, say the performance of raising signal Processing that can be to a certain degree as this representative article, still the problem of existence is to lack algorithm fast, can not be applied in the engineering system.And multiparameter is estimated as a kind of direct wide correlation process method, though can handle echo data fast, not matching of model can bring big evaluated error.
Summary of the invention
The objective of the invention is to the deficiency that exists at prior art, provide a kind of ultra-wideband ground-penetrating radar (uw-gpr) wide correlation process method based on time frequency analysis, estimated signal parameter fast and accurately, and improve the quality of imaging, reach the practical function of through engineering approaches.
For realizing such purpose, the present invention at first carries out time frequency analysis to echoed signal, and then obtains to represent the instantaneous parameters of non-stationary signal characteristic: instantaneous centre frequency, instant bandwidth and instantaneous dominant frequency.Utilize instantaneous centre frequency and instant bandwidth to finish frequency filtering, reduce repeatedly the interference of reflection wave, make to form wide match relation between the female ripple of echoed signal and radar emission echo signal.Utilize instantaneous centre frequency and female ripple to estimate contraction-expansion factor and set up to mate female ripple simultaneously, thereby transfer the biparametric optimization problem to one-parameter matched filtering time delay estimation problem, obtain the optimum time delay estimation of echo signal and the echoed signal that strengthens.
The wide correlation process method of ultra-wideband ground-penetrating radar (uw-gpr) based on time frequency analysis of the present invention comprises following concrete steps:
1. pre-service
The three-dimensional echo data of ground penetrating radar is carried out the average of horizontal and vertical direction, obtain the average echo data of vertical direction.Therefrom select the tie point of second and the 3rd echo to carry out data truncation, suppress direct wave as truncation points.Reject the echo data part of front, the echo data of remainder is carried out subsequent treatment as the data that contain signal.
Because ground penetrating radar echo signals is by directly the backward scattered wave of coupled waves, ground-reflected wave, the discontinuous generation of underground medium, random disturbance etc. constitute between dual-mode antenna.Direct wave by direct coupled waves and ground return wave component directly influences the echo echo signal.Because the relative echo signal of direct wave has a bigger mistiming, so the present invention blocks the inhibition direct wave by the data time axle.
2. the echoed signal time frequency analysis obtains instantaneous parameters
Ground penetrating radar echo data after blocking is carried out time frequency analysis, calculating pseudo-Wingner (Eugene Wigner) distributes, and then acquisition comprises the instantaneous parameters of instantaneous centre frequency, instant bandwidth and instantaneous dominant frequency, the instantaneous centre frequency of corresponding instantaneous energy maximum is represented target primary event wave frequency, and corresponding instant bandwidth is represented the bandwidth of target primary reflection.
Because ground penetrating radar echo signals is non-stationary, can obtain the transient power spectrum by time frequency analysis.Because transient power spectrum is the bidimensional variable, big many of the more classical power spectrum of its quantity of information, unsuitable subsequent treatment.Therefore can adopt several instantaneous parameterses that whole signal spectrum is characterized, as centre frequency, spectrum width and dominant frequency, corresponding to instantaneous centre frequency, instant bandwidth and instantaneous dominant frequency.
3. frequency domain filtering extracts the centre frequency echoed signal
Make the centre frequency of frequency domain filter and instantaneous centre frequency and the instant bandwidth that bandwidth equals ceiling capacity respectively, carry out the frequency domain filter design.The echo data that direct wave is rejected carries out filtering by frequency domain filter, suppresses undesired signal, extracts the centre frequency echoed signal.
Because echoed signal is by the stack of the waveform of a series of different due ins, different amplitudes, thereby the ripple that has blured each reflection aspect reaches the size of time and reflection coefficient.From frequency domain is exactly that target echo signal is disturbed by the reflection wave of a series of different frequency (comprising repeatedly reflection wave).Therefore utilize instantaneous centre frequency and the instant bandwidth estimated to carry out bandpass filtering, the filtering interfering echo is eliminated echo distortion, makes that the target echo after the filtering is similar to the wavelet that radar antenna is launched, and meets the condition of wide relevant treatment.
4. mate female ripple based on instantaneous centre frequency and female wave structure
Be divided by according to female wave frequency of instantaneous centre frequency of estimating and ground penetrating radar emission and obtain the contraction-expansion factor of echoed signal.The female ripple of radar emission is carried out match, and then carry out the female ripple of data compression acquisition coupling based on the inverse of compressibility factor.
The main thought of wide relevant treatment is exactly by the introducing contraction-expansion factor, and the echoed signal of gained has matching relationship with the female ripple that stretches.Can obtain the flexible factor of echoed signal according to the instantaneous centre Frequency Estimation of front and female wave frequency of emission, and then female ripple be carried out data compression process, make up the female ripple of coupling according to contraction-expansion factor.
5. time delay estimation and signal enhancing are carried out in matched filtering
At filtering data that has obtained and the female ripple of coupling, make the two-parameter estimation problem of wide relevant treatment be converted into one-parameter--the estimation problem of-time delay.The delay time estimation method of employing matched filtering can obtain the optimum time delay of echo signal to be estimated, and the echoed signal that strengthens.
The innovative point of technical solution of the present invention is to utilize time frequency analysis to extract the instantaneous centre frequency and the bandwidth of echoed signal, carry out frequency domain filtering to satisfy the precondition of wide relevant treatment, carry out accurate signal filtering and parameter estimation by structure female ripple of coupling and matched filtering.The present invention reduces the complexity of algorithm greatly, the significant and practical value for the application system of reality, particularly hand tool.
Description of drawings
Fig. 1 is the wide correlation process method schematic flow sheet of ultra-wideband ground-penetrating radar (uw-gpr) of the present invention.
As shown in the figure, the per pass data of ground penetrating radar echo are obtained instantaneous centre frequency and instant bandwidth through the influence of pre-service rejecting direct wave through time frequency analysis.The female ripple of instantaneous centre frequency and radar emission is released contraction-expansion factor, and then by female ripple is mated in the flexible acquisition of launching female ripple.Adopt instantaneous centre frequency and instant bandwidth to carry out frequency domain filtering simultaneously, have correlationship between filtered signal and the female ripple of coupling, carry out matched filtering estimation time delay parameter and signal and strengthen.
Fig. 2 is wide relevant treatment effect comparison figure.
Among Fig. 2, (a) for the echo average data shows, (b) being the demonstration of three typical tangent of raw data, (c) is the result of direct wide relevant treatment, (d) be wide relevant treatment result, (e) be based on the wide relevant treatment result's of time frequency analysis 3-D display based on time frequency analysis.
Embodiment
In order to understand technical scheme of the present invention better, embodiments of the present invention are further described below in conjunction with accompanying drawing.
The practical wide correlation process method schematic flow sheet of ultra-wideband ground-penetrating radar (uw-gpr) that Fig. 1 proposes for the present invention.The concrete implementation detail of each several part is as follows:
1. pre-service
The three-dimensional echo data of ground penetrating radar is carried out the average of horizontal and vertical direction, obtain the average echo data of vertical direction, shown in Fig. 2 (a).Therefrom select the tie point of second and the 3rd echo to carry out data truncation, suppress direct wave as truncation points.The interface point that can see the second and the 3rd echo is 65, therefore chooses 65 truncation points as echoed signal.Reject preceding 65 points, the echo data of remainder is carried out signal Processing.
2. the echoed signal time frequency analysis obtains instantaneous parameters
Ground penetrating radar echo data to after blocking carries out time frequency analysis, calculates pseudo-Wingner and distributes, and then can obtain comprising the instantaneous parameters of instantaneous centre frequency, instant bandwidth and instantaneous dominant frequency.
(1) echo data that pre-service obtains at per pass calculates its pseudo-Wigner distribution, and computing formula is as follows:
PWD f ( l , m ) = 2 Σ n = 0 N - 1 e - α n 2 s * ( l - n ) s ( l + n ) e - j ( 4 π / N ) mn
In the formula: s (t) is a time-domain signal function (analytical form) to be analyzed, s *(t) be its conjugate function, h (τ) adopts the Gaussian window function, and the width of window is 100 sample intervals.L, m=0,1,2 ..., N-1 is express time and frequency respectively.
(2) transient parameter calculates
Consider that whole signal spectrum can be characterized by instantaneous parameters, comprises the instantaneous centre frequency f i(t), instantaneous frequency range σ f(t), instantaneous centre frequency f d(t).Corresponding calculated is:
f i ( t ) = ∫ 0 ∞ fW ( t , f ) df ∫ 0 ∞ W ( t , f ) df
σ f 2 ( t ) = ∫ 0 ∞ [ f - f i ( t ) ] 2 W ( t , f ) df ∫ 0 ∞ W ( t , f ) df
f d 2 ( t ) = ∫ 0 ∞ f 2 W ( t , f ) df ∫ 0 ∞ W ( t , f ) df
And f d 2 ( t ) = f i 2 ( t ) + σ f 2 ( t ) . Wherein, (t f) is instantaneous power spectrum (pseudo-Wigner distribution) to W.The instantaneous centre frequency of corresponding instantaneous energy maximum is represented target primary event wave frequency, and corresponding instant bandwidth is represented the bandwidth of target primary reflection.
3. frequency domain filtering extracts the centre frequency echoed signal;
Utilize instantaneous centre frequency and the instant bandwidth estimated to carry out Design of Bandpass.By setting cutoff frequency, radar signal is carried out filtering at frequency domain.Removed the high frequency noise of signal, in having kept, the low frequency useful signal.Make the target echo after the filtering be similar to the wavelet that radar antenna is launched, meet the condition of matched filtering.
4. mate female ripple based on instantaneous centre frequency and female wave structure;
Can obtain the flexible factor of echoed signal, general contraction-expansion factor s ∈ (0,1) for the earth according to the instantaneous centre Frequency Estimation of front and female wave frequency of emission.By the match to the female ripple of radar emission, and then carry out data compression, ratio of compression is typ (1/S), and typ () expression is promptly got the equal proportion wavelet nearest with it to the typification of ratio of compression, and typical ratio of compression is respectively 1,1.5,2,2.5,3,3.5,4.
5. time delay estimation and signal enhancing are carried out in matched filtering.
By the female ripple of structure coupling the two-parameter estimation problem of wide relevant treatment is converted into one-parameter--the estimation problem of-time delay.The delay time estimation method of employing matched filtering obtains the optimum time delay of echo signal to be estimated, and the echoed signal that strengthens.
At the actual detection data of ultra-wideband ground-penetrating radar (uw-gpr), adopt based on the wide correlation process method of time frequency analysis and handle the correlated results that obtains Fig. 2 demonstration.Wherein Fig. 2 (b) is the demonstration of three typical tangent of raw data; Fig. 2 (c) is the result of direct wide relevant treatment; Fig. 2 (d) is for the present invention is based on the wide relevant treatment result of time frequency analysis; Fig. 2 (e) is based on the wide relevant treatment result's of time frequency analysis 3-D display.Comparison diagram 2 (b) (c), (d) and (e), can see that the wide correlation process method that the present invention is based on time frequency analysis can effectively handle echoed signal, can see two tubular articles that bury ground from last result.Contrast direct wide relevant treatment, the enhancing of signal has had further raising.Simultaneously from whole performing step as can be known, method of the present invention is easy to realize, thereby provides a technology implementation method for the through engineering approaches of ground penetrating radar.

Claims (1)

1, the wide correlation process method of a kind of ultra-wideband ground-penetrating radar (uw-gpr) based on time frequency analysis is characterized in that comprising following concrete steps:
1) pre-service: the three-dimensional echo data of ground penetrating radar is carried out the average of horizontal and vertical direction, obtain the average echo data of vertical direction, therefrom select the tie point of second and the 3rd echo to carry out data truncation as truncation points, suppress direct wave, reject the echo data part of front, the echo data of remainder is carried out subsequent treatment as the data that contain signal;
2) the echoed signal time frequency analysis obtains instantaneous parameters: the ground penetrating radar echo data after blocking is carried out time frequency analysis, calculate pseudo-Wigner distribution, and then acquisition comprises the instantaneous parameters of instantaneous centre frequency, instant bandwidth and instantaneous dominant frequency, the instantaneous centre frequency of corresponding instantaneous energy maximum is represented target primary event wave frequency, and corresponding instant bandwidth is represented the bandwidth of target primary reflection;
3) frequency domain filtering extracts the centre frequency echoed signal: make the centre frequency of frequency domain filter and instantaneous centre frequency and the instant bandwidth that bandwidth equals ceiling capacity respectively, carry out the frequency domain filter design, the echo data that direct wave is rejected carries out filtering by frequency domain filter, suppress undesired signal, extract the centre frequency echoed signal;
4) mate female ripple based on instantaneous centre frequency and female wave structure: being divided by according to female wave frequency of instantaneous centre frequency of estimating and ground penetrating radar emission obtains the contraction-expansion factor of echoed signal, the female ripple of radar emission is carried out match, and then carry out the female ripple of data compression acquisition coupling based on the inverse of compressibility factor;
5) time delay estimation and signal enhancing are carried out in matched filtering: at filtering data that has obtained and the female ripple of coupling, make the two-parameter estimation problem of wide relevant treatment be converted into one-parameter--the estimation problem of-time delay, the delay time estimation method of employing matched filtering obtains the optimum time delay of echo signal to be estimated, and the echoed signal that strengthens.
CN 200410017540 2004-04-08 2004-04-08 Width realtive processing method of super broadband ground finding radar based on time frequency analysis Expired - Fee Related CN1259629C (en)

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Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN100501425C (en) * 2007-01-08 2009-06-17 武汉大学 High-frequency chirp radar directional diagram measuring method
CN101363913B (en) * 2008-09-27 2011-01-12 中国航天科技集团公司第五研究院第五0四研究所 Signal processing method of fan-shaped beam circular cone scanning microwave scatterometer
CN102288625A (en) * 2011-07-08 2011-12-21 李典基 Channel concrete lining nondestructive testing system
CN102298160A (en) * 2011-05-18 2011-12-28 西安交通大学 Method for tracking data layer position of ground penetrating radar
CN101738602B (en) * 2008-11-26 2012-08-29 中国科学院电子学研究所 Echo data preprocessing method for pseudorandom sequences applied to ground penetrating radar
CN104020498A (en) * 2014-05-16 2014-09-03 桂林电子科技大学 Ground penetrating radar signal preprocessing method and device based on instantaneous amplitude parameters

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN100501425C (en) * 2007-01-08 2009-06-17 武汉大学 High-frequency chirp radar directional diagram measuring method
CN101363913B (en) * 2008-09-27 2011-01-12 中国航天科技集团公司第五研究院第五0四研究所 Signal processing method of fan-shaped beam circular cone scanning microwave scatterometer
CN101738602B (en) * 2008-11-26 2012-08-29 中国科学院电子学研究所 Echo data preprocessing method for pseudorandom sequences applied to ground penetrating radar
CN102298160A (en) * 2011-05-18 2011-12-28 西安交通大学 Method for tracking data layer position of ground penetrating radar
CN102288625A (en) * 2011-07-08 2011-12-21 李典基 Channel concrete lining nondestructive testing system
CN104020498A (en) * 2014-05-16 2014-09-03 桂林电子科技大学 Ground penetrating radar signal preprocessing method and device based on instantaneous amplitude parameters
CN104020498B (en) * 2014-05-16 2016-10-19 桂林电子科技大学 Gpr Signal preprocess method based on instantaneous amplitude-frequency parameter and device

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