CN104375128A - Fast high maneuvering target accumulating and detecting method based on cross-correlation functions - Google Patents

Abstract

The invention provides a fast high maneuvering target accumulating and detecting method based on cross-correlation functions, belongs to the technical field of radar, and relates to a target detecting method. The method can be used for efficiently processing radar detection based on multiple phase-coherence pulse echoes in a white Gaussian noise environment. At first, the cross-correlation functions of adjacent pulses of echo signals are utilized for correcting the distance movement of a target, cross-correlation operation for the second time is used for correcting the Doppler movement of the target, and finally Flourier transformation (FFT) is used for achieving effective accumulation of target energy. As all kinds of operation can be achieved by utilizing the fast Fourier transformation, the operation amount of the detecting method is greatly reduced, phase-coherence accumulation of the variable accelerated target energy can be achieved fast, the fast detection ability of the radar to the high-speed maneuvering target can be effectively improved, and the method is beneficial for engineering realization.

Description

A kind of highly maneuvering target Rapid Accumulation detection method based on cross correlation function

Technical field

The invention belongs to Radar Technology field, relate to object detection method, can be used for efficiently processing based on the detections of radar of multiple coherent pulse echo in white Gaussian noise environment.

Background technology

Along with the development of science and technology, the especially development of aeronautical technology and high-speed target, increasing maneuvering target appears at Radar Signal Detection field.As near space high hypervelocity aircraft, its flying speed up to 25 Mach, and can do varying accelerated motion, and maneuverability is extremely strong; Also have the targets such as ballistic missile, snakelike Maneuver Penetration can be done.On the other hand, stealth technology increasingly mature, makes the Radar Cross Section of the maneuvering targets such as near space vehicle sharply reduce, causes radar return very faint, reduce the detection perform of radar.

Utilize signal processing method to realize the detection to low detectivity target, means are flexible, and cost is lower, has good application prospect.Usually long time integration can be utilized to increase the energy of target, reach the requirement improving Signal-to-Noise, thus improve radar to the detectability of target.Long time integration technology, according to the phase information whether utilizing echo signal, can be divided into non-inherent accumulation (only utilizing signal amplitude information) and correlative accumulation (simultaneously utilizing amplitude and the phase information of signal) two kinds.Compared with non-inherent accumulation technology, correlative accumulation utilizes kinetic characteristic and the doppler information of target, effectively can improve the detection perform of target inband energy and radar.The key of long-time phase-coherent accumulation is just the effective superposition to target echo energy.But the high speed of target and very strong maneuverability can make target echo envelope peak appear in different range units, are called range walk effect; On the other hand when long-time phase-coherent accumulation, the acceleration of target and rate of acceleration change can cause phase of echo to change, and the Doppler frequency of target will cross over multiple doppler cells, are called that Doppler walks about effect, makes target energy disperse at frequency domain.Range walk and Doppler walk about and traditional objective accumulation detection method can be made to lose efficacy.

In existing Research Literature, the method that maneuvering target correlative accumulation under walking about for range walk and Doppler detects, mainly contain two classes: a class is the method based on keystone conversion, but these class methods need to carry out interpolation arithmetic, also need to carry out the search of doppler ambiguity multiple, calculated amount is large simultaneously; Another kind of is the method converted based on Radon, typically has Radon-FT converter technique and Radon-FRFT converter technique, and these class methods need to carry out multi-dimensional search in the kinematic parameter space (distance, speed, acceleration etc.) of target, calculate more complicated.Generally speaking, existing method all needs to carry out interpolation arithmetic or multidimensional search operation, and computing is complicated, very time-consuming; Be unfavorable for detecting in real time fast of maneuvering target.

Summary of the invention

The deficiency that the present invention is directed to background technology proposes a kind of highly maneuvering target Rapid Accumulation detection method based on cross correlation function, solve the Rapid Accumulation test problems doing the high-speed target of variable accelerated motion, the method does not need to carry out any interpolation arithmetic or search operation, thus it is little to reach calculated amount, be easy to Project Realization, be conducive to improving radar to the object of the real-time detection perform of high-speed maneuver target.

Technical scheme of the present invention is a kind of highly maneuvering target Rapid Accumulation detection method based on cross correlation function, and the method comprises the steps:

Step 1: radar return signal, and the multiple pulse echo data received are designated as m=1,2...N, wherein, represent the time needed for a pulse, t _mrepresent the time needed for multiple pulse, N represents total pulse number, and the echo data received can regard a two-dimensional array as;

Step 2: paired pulses echo edge fast fourier transform is done to frequency of distance territory in direction, obtains frequency domain data z (f, the t of echo distance dimension _m); Wherein f represents frequency of distance;

Step 3: note z (f, t _m) at t _mon direction, the 1 to the N-1 pulse data is z ₁(f, t _m), m=1,2...N-1; Note z (f, t _m) at t _mon direction, the 2 to the N number of pulse data is z ₂(f, t _m); Calculate radar pulse echo cross correlation function computing formula is as follows

$R_1(\hat{t},t_m)=\underset{f}{\mathrm{IFT}}\left[z_1(f,t_m){z_2}^{*}(f,t_m)\right]$

Wherein, represent with frequency of distance f for variable does inverse Fourier transform (IFT), z ₂ ^*(f, t _m) represent z ₂(f, t _m) conjugation;

Step 4: to what obtain m=1,2...N-1, edge fast fourier transform is done in direction, obtains signal data R ₁(f, t _m); Then signal is calculated cross correlation function computing formula is as follows

$R_2(\hat{t},t_m)=\underset{f}{\mathrm{IFT}}\left[R_A(f,t_m){R_B}^{*}(f,t_m)\right]$

Wherein, R _a(f, t _m) represent R ₁(f, t _m) along t _mfront N-2 pulse data on direction, R _b(f, t _m) represent R ₁(f, t _m) along t _mrear N-2 pulse data on direction; R _b ^*(f, t _m) represent R _b(f, t _m) conjugation;

Step 5: by the cross correlation function calculated along t _mdimension does Fourier transform (FT), obtains correlative accumulation result, is designated as peak value in correlative accumulation result is the target of detection.

The present invention carries out target detection owing to utilizing the method for pulse accumulation, can effective restraint speckle, simultaneously owing to utilizing cross correlation function correction target range walk and Doppler to walk about, make signal energy to carry out coherent superposition, improve the detection perform of echo signal to noise ratio (S/N ratio) and radar.In addition, because the operation that the present invention is all can utilize Fast Fourier Transform (FFT) and Inverse Fast Fourier Transforms to realize, thus reduce the operand of detection method greatly, realize rapidly becoming the correlative accumulation accelerating target energy, effectively can improve the quick detectability of radar to high-speed maneuver target, be conducive to Project Realization.

Accompanying drawing illustrates:

Fig. 1 of the present inventionly realizes general flow chart;

Fig. 2 represents the pulse echo that radar receives;

Fig. 3 is the result after radar echo signal matched filtering;

Fig. 4 represents the cross correlation function of radar echo signal adjacent pulse result;

Fig. 5 represents the accumulation result of the inventive method.

Embodiment:

Specific implementation of the present invention is provided below in conjunction with Fig. 1.

The radar return of the high speed highly maneuvering target adopting computational science software matlab R2008a emulation to produce, target number is 1, the initial distance 200km of the relative radar of target, and target radial speed is 180m/s, and target radial acceleration is 60m/s ², target radial rate of acceleration change is 50m/s ³, radar emission carrier frequency is 10GHz, and range resolution is 15 meters, and radar pulse repetition frequency is 200Hz, comprises 403 pulses in the correlative accumulation time, and signal to noise ratio (S/N ratio) is 4dB.

The first step: radar receives multiple pulse echo signal, as shown in Figure 2, because echo signal to noise ratio (S/N ratio) is lower, target is submerged in noise, can not highlight, be unfavorable for target detection.Result after radar echo signal matched filtering as shown in Figure 3, can be clearly seen that, the energy distribution of target, at different range units, namely there occurs range walk.

Second step: the cross correlation function calculating echoed signal adjacent pulse cross correlation function result as shown in Figure 4, can be seen from this figure, and after cross correlation function process, target energy has dropped in same range unit, and range walk is corrected.

3rd step: calculate signal adjacent pulse between cross correlation function then right do Fourier transform (FFT) along slow time dimension, obtain correlative accumulation result, as shown in Figure 5.Owing to completing range walk by cross correlation process above and Doppler walks normal moveout correction, the energy of target is able to coherent superposition, thus can highlight target, is conducive to the detection of radar to target.

Claims (1)

1., based on a highly maneuvering target Rapid Accumulation detection method for cross correlation function, the method comprises the steps:

Step 1: radar return signal, and the multiple pulse echo data received are designated as m=1,2...N, wherein, represent the time needed for a pulse, t _mrepresent the time needed for multiple pulse, N represents total pulse number, and the echo data received can regard a two-dimensional array as;

Step 2: paired pulses echo edge fast fourier transform is done to frequency of distance territory in direction, obtains frequency domain data z (f, the t of echo distance dimension _m); Wherein f represents frequency of distance;

Step 3: note z (f, t _m) at t _mon direction, the 1 to the N-1 pulse data is z ₁(f, t _m), m=1,2...N-1; Note z (f, t _m) at t _mon direction, the 2 to the N number of pulse data is z ₂(f, t _m); Calculate radar pulse echo cross correlation function computing formula is as follows

$R_1(\hat{t},t_m)=\underset{f}{\mathrm{IFT}}\left[z_1(f,t_m){z_2}^{*}(f,t_m)\right]$

Wherein, represent with frequency of distance f for variable does inverse Fourier transform (IFT), z ₂ ^*(f, t _m) represent z ₂(f, t _m) conjugation;

Step 4: to what obtain m=1,2...N-1, edge fast fourier transform is done in direction, obtains signal data R ₁(f, t _m); Then signal is calculated cross correlation function computing formula is as follows

$R_2(\hat{t},t_m)=\underset{f}{\mathrm{IFT}}\left[R_A(f,t_m){R_B}^{*}(f,t_m)\right]$

Wherein, R _a(f, t _m) represent R ₁(f, t _m) along t _mfront N-2 pulse data on direction, R _b(f, t _m) represent R ₁(f, t _m) along t _mrear N-2 pulse data on direction, R _b ^*(f, t _m) represent R _b(f, t _m) conjugation;

Step 5: by the cross correlation function calculated along t _mdimension does Fourier transform (FT), obtains correlative accumulation result, is designated as peak value in correlative accumulation result is the target of detection.