CN102628937A - Radar detection method based on generalized keystone transformation and non-coherent accumulation - Google Patents

Abstract

The invention discloses a radar detection method based on generalized keystone transformation and non-coherent accumulation, wherein the method mainly solves the detection problem of a high speed and highly accelerated target in a strong Gaussian white noise background. The method is implemented by the following steps: (1) generating radar target multiple-pulse echoes with Gaussian white noise added, and performing frequency domain pulse compression; (2) correcting range curvature of the pulse-compressed echoes by using the generalized keystone transformation; (3) performing fuzzy compensation on the curvature-corrected echoes by using a fuzzy factor; (4) performing non-coherent accumulation on the fuzzy-compensated echoes, and performing velocity compensation and slow time dimensional quadratic term compensation on the echoes by using a target velocity obtained in the non-coherent accumulation; (5) performing coherent accumulation on the slow time dimensional quadratic term compensated echoes to obtain the target to be detected. The method provided in the invention can eliminate effects of the range curvature and migration of the echoes on energy accumulation, can reduce computation of velocity search, and can be used in the detection of the target in the strong Gaussian white noise background.

Description

Radar detecting method based on broad sense keystone conversion and the accumulation of non-coherent

Technical field

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

Background technology

In the Radar Targets'Detection field; Can run into the situation that target to be detected is a high-speed motion; This class targets has very high speed and acceleration usually; Traditional method is that a plurality of pulse echos are directly carried out slow time dimension FFT, if range walk then can not take place when being low-speed motion in target, thus the purpose that can the energy accumulation of each time target echo got up and to reach target detection come out.But because target is a high-speed motion; Make and bigger range walk can take place at pulse internal object integration time; And the high acceleration of target also can cause the range curvature of echo envelope, if the paired pulses echo directly carries out slow time dimension FFT, can only get up the energy accumulation of same range unit; The signal gross energy is dispersed on a plurality of range units; The peak value of gained pulse accumulation is much lower when range walk and range curvature do not take place, thereby can not obtain good testing result, when serious even can lose objects; Existing research is introduced with the keystone method can get rid of the influence of the range walk of target generation to accumulation; But for reaching good accumulation, the range curvature of the echo envelope that the high acceleration in the time of also need be with target travel causes is removed the influence of accumulation, does not also have good method to solve at present.

Under the movable information condition of unknown of target; If obtain the velocity information of target through the method for accumulation; Usual method is, at first sets very big speed search scope and certain speed step-size in search, then each search speed of calculating of foundation echo envelope that can cause number of walking about; The paired pulses echo carries out the envelope ring shift; Again the pulse echo of carrying out after the envelope ring shift is done non-coherent accumulation, at last that each is the possible result that search speed accumulated compares, and the corresponding speed of maximum accumulation is the velocity estimation value of target.The result who does like this is to be cost with very high search arithmetic amount, therefore, is necessary to look for a kind of method that reduces operand.

Summary of the invention

The objective of the invention is to deficiency to above-mentioned prior art; A kind of radar detecting method based on broad sense keystone conversion and the accumulation of non-coherent is proposed; To reduce the operand of target velocity search; Get rid of high acceleration to the target energy effect of accumulation, thereby help improving radar the high detection performance of quickening target of high speed.

For realizing above-mentioned purpose, radar target detection method of the present invention comprises the steps:

1) approximate model and the noise model with the high accelerated motion target of radar high speed is expressed as respectively And d (l, t _m);

2) according to target approximate model and noise model, obtain the radar pulse echo:

And paired pulses echo

With the fast time

Be FFT for variable and transform to the frequency of distance territory, obtain frequency domain data z (f, the t of echo apart from dimension _m), wherein f representes frequency of distance;

3) will be apart from frequency domain data z (f, the t of dimension _m) do the frequency domain pulse compression along the distance dimension, the data after the pulse compression are designated as z ' (f, t _m), and to the data z ' after this pulse compression (f, t _m) in slow time variable t _mWith new time variable τ _mReplace, the variable alternate form does The data that obtain after the variable replacement are designated as z ' (f, τ _m);

4) setting fuzzy factor range is [n _Min, n _Max], n wherein _MinMinimum, n _MaxMaximum, N altogether, and all be positive integer, with data z ' (f, the τ after the fuzzy factor pair variable replacement in this scope _m) carrying out fuzzy compensation, the echo data after the compensation is designated as z ' _i(f, τ _m), i=1 ... N;

5) to the echo frequency domain data z ' behind the fuzzy compensation _i(f, τ _m), i=1 ... N carries out interior the inserting of time domain that p is ordered in each range unit, and the data after inserting in the time domain are designated as

I=1 ... N;

6) utilize data after inserting in the time domain, the echo envelope range walk is counted the umber of pulse w in k and the same range unit when calculating target velocity and being v _k

7) according to the target friction speed next time the pitch of waves from number k and the same range unit umber of pulse w of walking about _kDifference, the data after inserting in the time domain are carried out ring shift, and the group of the N after ring shift echo data are carried out non-coherent accumulation, obtain N and organize non-coherent accumulation, be designated as I=1 ... N, wherein || expression be modulo operation;

8) N is organized non-coherent accumulation I=1 ... N compares, and getting and wherein accumulating the maximum factor of corresponding fuzzy as a result of peak value is the velocity ambiguity factor of n of target _kEstimated value, be designated as

And the corresponding speed of the accumulation peak value of getting this maximum is fuzzy back target initial velocity v ₀Estimated value, be designated as

9) utilize the objective fuzzy obtain after initial velocity estimated value

with the target initial velocity estimated value

that estimation obtains the echo frequency numeric field data

corresponding with fuzzy factor estimated value carried out velocity compensation then with the estimated value

that fuzzy factor estimated value

is calculated the target initial velocity; Echo data after will compensating again transforms to apart from time domain, is designated as

apart from time domain data after the conversion

10) to conversion later apart from time domain data

Carry out the search of frequency modulation rate with the method for Dechirp, obtain frequency modulation rate γ _aEstimated value, be designated as And then obtained the estimated value of target travel acceleration

11) with the estimated value

of the aimed acceleration that obtains the data after the velocity compensation

are carried out the compensation of slow time dimension quadratic phase item; And the data after the compensation are done the coherent accumulation of slow time dimension, the peak value of coherent accumulation is the target of detection.

The present invention can effectively suppress noise owing to utilize the method for pulse accumulation to carry out target detection; Simultaneously owing to utilize broad sense keystone conversion correction target envelope range curvature, make the result of non-coherent accumulation after the correction distance bending more near the target echo actual energy; Owing to utilize the method for velocity ambiguity compensation to dwindle the hunting zone of target initial velocity, make that the non-coherent accumulation operand after broad sense keystone conversion reduces greatly in addition.

Below in conjunction with accompanying drawing working of an invention is described in detail.

Description of drawings

Fig. 1 is a realization general flow chart of the present invention;

Fig. 2 is the testing result figure that adopts existing conventional sense method;

Fig. 3 is the testing result figure that adopts existing optimum detection methodology;

Fig. 4 is the testing result figure that adopts the inventive method.

Embodiment

With reference to Fig. 1, concrete performing step of the present invention is following:

Step 1, the radar target multiple-pulse echo of generation plus noise.

1a) the approximate model of radar target multiple-pulse echo:

$s(\hat{t},t_m)=A_0\mathrm{rect}\left[\frac{t-\frac{2\hat{R}\left(t_m\right)}{c}}{T_p}\right]\exp \left[\mathrm{j\π\γ}{(\hat{t}-\frac{2R\left(t_m\right)}{c})}^2\right]\exp [-j\frac{4\mathrm{\π}{f}_{c}R\left(t_m\right)}{c}]\exp (-j\frac{{4\mathrm{\πf}}_{c}v\hat{t}}{c})$

In the formula, $\mathrm{Rect}\left(u\right)=\left\{\begin{array}{cc}1& \left|u\right|\≤1/2\\ 0& \left|u\right|>1/2\end{array}\right.,$ T _pBe pulsewidth, γ is the frequency modulation rate,

Be the fast time, t is full-time, and m is an integer, T _rBe pulse-recurrence time, f _cBe radar emission signal carrier frequency, t _m=mT _rBe the slow time, A ₀Be the intensity of scattering point echo,

Be t _mTarget is to the distance of radar, R constantly ₀Be target initial time distance, v is a target velocity, and a is an aimed acceleration, and c is the light velocity;

1b) noise model:

Noise in the continuous N time echo is expressed as with matrix form:

Wherein, l is the range unit label, the noise power of l range unit of u (l) expression, g (l, t _m) be the noise phase of l range unit in m the pulse, column vector g (l) is and u (l) statistical independent M ties up the multiple Gaussian random variable of zero-mean, M representes the transponder pulse number, m=1,2 ..., M;

1c) utilize the approximate model of radar target multiple-pulse echo

And noise

Generate the radar target multiple-pulse echo of plus noise: $z(\hat{t},t_m)=s(\hat{t},t_m)+d(\hat{t},t_m).$

Step 2 is FFT to the radar target multiple-pulse echo of plus noise along the distance dimension.

Owing to walking about from the unit and the range curvature inconvenience, so paired pulses echo apart from the skip distance of the direct processing target of time domain

Will be with the fast time

Be FFT for variable and transform to the frequency of distance territory, obtain frequency domain data z (f, t _m), what wherein FFT represented is Fast Fourier Transform (FFT), f representes frequency of distance.

Step 3, frequency domain data z (f, the t of paired pulses echo _m) carry out pulse compression.

3a) frequency domain data z (f, the t through following formula paired pulses echo _m) do the frequency domain pulse compression:

$H\left(\hat{t}\right)=\mathrm{rect}\left(\frac{\hat{t}}{T_p}\right)\exp (-\mathrm{j\π\γ}{\hat{t}}^2)$

In the formula,

The indicating impulse compression function, $\mathrm{Rect}\left(u\right)=\left\{\begin{array}{cc}1& \left|u\right|\≤1/2\\ 0& \left|u\right|>1/2\end{array}\right.,$ Be the fast time, T _pBe pulsewidth, γ is the frequency modulation rate;

3b) frequency of distance-slow time domain data with the pulse echo after the pulse compression are designated as z ' (f, t _m), these data have comprised target echo and noise information, and this instance only carries out theoretical analysis to target echo, so write out the concrete form of the later target echo signal of pulse pressure is:

$s_1(f,t_m)=A^{\′}\mathrm{rect}\left(\frac{f}{\mathrm{\Δf}}\right)\exp (-j2\mathrm{\πf}(\frac{{2R}_0}{c}+\frac{f_d}{\mathrm{\γ}}))\exp (-j2\mathrm{\π}\frac{f_d(f_c+f)}{f_c}{t}_m)$

$\·\exp (-j\frac{{\mathrm{\π\γ}}_a(f_c+f)}{f_c}{t}_m^2),$

In the formula, A ' expression is done the echo strength after the frequency pulse pressure to target echo, and Δ f is the radar emission signal bandwidth,

Be the Doppler frequency of target, λ is a radar wavelength, and target is to the distance of radar

R ₀Be target initial time distance, v is a target velocity, and a is an aimed acceleration, t _mBe the slow time, f _cBe radar emission signal carrier frequency, c is the light velocity;

Because target high-speed motion; Make the envelope of target echo signal that the skew that is directly proportional with Doppler frequency can take place; The distance of its skew is

but the distance of this skew is identical for each time echo, does not therefore consider.

Step 4 is utilized broad sense keystone conversion correction target echo range curvature.

4a) because the rapid speed of target, and the repetition frequency of radar transmitted pulse is lower, therefore can cause target generation velocity ambiguity, so the Doppler frequency of target is expressed as:

f _d＝f _d0+n _kPRF ，

In the formula, f _D0Be the later Doppler frequency of velocity ambiguity, n _kBe the fuzzy factor, PRF is a pulse repetition rate;

4b) with the expression of target echo after the expression substitution pulse compression of target Doppler frequency, the expression that the target echo that obtains is new is:

$s_2(f,t_m)=A^{\′}\mathrm{rect}\left(\frac{f}{\mathrm{\Δf}}\right)\exp (-j2\mathrm{\πf}(\frac{{2R}_0}{c}+\frac{f_d}{\mathrm{\γ}}))\exp (-j2\mathrm{\π}\frac{f_{d0}(f_c+f)}{f_c}{t}_m)$

$\·\exp (-j\frac{{2\mathrm{\πn}}_k\mathrm{fPRF}}{f_c}{t}_m)\exp (-j2\mathrm{\πPRF}{n}_k{t}_m)\exp (-j\frac{{\mathrm{\π\γ}}_a(f_c+f)}{f_c}{t}_m^2),$

In the formula, A ' expression is done the echo strength after the frequency pulse pressure to target echo, and Δ f is the radar emission signal bandwidth,

Be the Doppler frequency of target, λ is a radar wavelength, and target is to the distance of radar R ₀Be target initial time distance, v is a target velocity, and a is an aimed acceleration, γ _aBe doppler frequency rate, t _mBe the slow time, f _cBe radar emission signal carrier frequency, c is the light velocity;

4c) phase place according to the 4th exponential term in the new expression of target echo after the pulse compression is the integral multiple of 2 π, and its value is 1, so after it is removed, obtain the new reduced representation formula s of target echo ₃(f, t _m) be:

$s_3\left({f,t}_m\right)=A^{\′}\mathrm{rect}\left(\frac{f}{\mathrm{\Δf}}\right)\exp (-j2\mathrm{\πf}(\frac{{2R}_0}{c}+\frac{f_d}{\mathrm{\γ}}))\exp (-j2\mathrm{\π}\frac{f_{d0}(f_c+f)}{f_c}{t}_m)$

$\·\exp (-j\frac{{2\mathrm{\πn}}_k\mathrm{fPRF}}{f_c}{t}_m)\exp (-j\frac{{\mathrm{\π\γ}}_a(f_c+f)}{f_c}{t}_m^2);$

4c) because the target travel acceleration is very big, so pulse echo is easy to generate range curvature, thereby can influence the result that pulse energy accumulates, for eliminating this influence, introduce broad sense keystone conversion, i.e. paired pulses compression back data z ' (f, t _m) slow time variable t _mIntroduce the variable alternate form

Pulse echo data after the variable replacement are designated as z ' (f, τ _m);

4d) paired pulses compression back target echo signal s ₃(f, t _m) carry out broad sense keystone conversion after, the target echo signal s that obtains ₄(f, τ _m) expression be:

$s_4\left({f,t}_m\right)=A^{\′}\mathrm{rect}\left(\frac{f}{\mathrm{\Δf}}\right)\exp (-j2\mathrm{\πf}(\frac{{2R}_0}{c}+\frac{f_d}{\mathrm{\γ}}))\exp (-j2\mathrm{\π}{f}_{d0}\frac{(f_c+f)}{f_c}\sqrt{\frac{f_c}{f_c+f}}{\mathrm{\τ}}_m)$

$\·\exp (-j\frac{{2\mathrm{\πn}}_k\mathrm{fPRF}}{f_c}\sqrt{\frac{f_c}{f_c+f}}{\mathrm{\τ}}_m)\exp (-j{\mathrm{\π\γ}}_a{\mathrm{\τ}}_m^2).$

Step 5 is carried out fuzzy compensation to the echo data after the broad sense keystone conversion.

5a) paired pulses echo data z ' (f, τ _m) in the analysis of target echo signal expression can know that its 3rd exponential term is the velocity ambiguity item, need in this instance to compensate to it;

5b) the fuzzy factor of n of target setting _kScope [n _Min, n _Max], n wherein _MinBe the fuzzy factor estimated value of minimum, n _MaxBe the fuzzy factor estimated value of maximum, total N, and be integer all, utilize the fuzzy factor in this scope, constructed fuction G (f, τ _mn _k) to data z ' (f, τ after the broad sense keystone conversion _m) utilize following formula to carry out fuzzy compensation:

$G(f,{\mathrm{\τ}}_m,n_k)=\exp \left(j\frac{{2\mathrm{\πn}}_{k}f}{f_c}\sqrt{\frac{f_c}{{f+f}_c}}{\mathrm{PRF\τ}}_m\right),$

In the formula, G (f, τ _mn _k) expression fuzzy compensation function, n _kThe fuzzy factor of expression, τ _mBe the slow time after variable changes, f representes frequency of distance, f _cBe radar emission signal carrier frequency, PRF is the repetition frequency of radar emission signal, and the pulse echo data behind the fuzzy compensation are designated as z ' _i(f, τ _m), i=1 ... N.

5c) with fuzzy compensation function G (f, τ _mn _k) target echo signal s to obtaining after the broad sense keystone conversion ₄(f, τ _m) carry out fuzzy compensation, the target echo signal s behind the fuzzy compensation that obtains ₅(f, τ _m) expression be:

$s_5(f,{\mathrm{\τ}}_m)=A^{\′}\mathrm{rect}\left(\frac{f}{\mathrm{\Δf}}\right)\exp (-j2\mathrm{\πf}(\frac{{2R}_0}{c}+\frac{f_d}{\mathrm{\γ}}))\exp (-j2\mathrm{\π}{f}_{d0}\frac{(f_c+f)}{f_c}\sqrt{\frac{f_c}{f_c+f}}{\mathrm{\τ}}_m)$

$\·\exp (-j{\mathrm{\π\γ}}_a{\mathrm{\τ}}_m^2).$

Step 6 is to the pulse echo data z ' behind the fuzzy compensation _i(f, τ _m), i=1 ... N carries out apart from insert in the time domain, is about to the data z ' of fuzzy compensation afterpulse echo _i(f, τ _m), i=1 ... N carries out interior the inserting of time domain of p point in each range unit, p=1, and 2,3, the data after inserting in the time domain are designated as

I=1 ... N inserts theoretical see for details with method " radar imagery technology " in the time domain.

Step 7, the range walk of echo envelope was counted the umber of pulse w in k and the same range unit when calculating target velocity was v _k

7a) the pulse echo data after the broad sense keystone conversion are after carrying out the velocity ambiguity compensation, and the target velocity scope is 0≤v≤v _MaxSo, only need the speed in this scope is estimated, calculate the fuzzyyest speed of target

According to the fuzzyyest speed v that obtains _Max, calculating target echo envelope range walk number is l=(p+1) * round (2v _Maxf _s/ cPRF) with same range unit in umber of pulse w _l=M/l, wherein PRF representes the radar transmitted pulse repetition frequency, and λ representes radar wavelength, and what round represented is the operation that rounds that rounds up, f _sBe the signal sampling frequency;

7b) count the umber of pulse w in l and the same range unit according to target echo envelope range walk _l, confirm speed search step delta v:

At first, get any two adjacent value l in the several 0～l-1 scopes of range walk ₁And l ₂, l ₁＜l ₂

Secondly, calculating generation range walk number is l ₁The time corresponding target velocity

With the range walk number takes place is l ₂The time corresponding target velocity $v_2=\frac{{\mathrm{Cl}}_2\mathrm{PRF}(p+1)}{2\mathrm{\Δ\; FM}};$

Then, use generation range walk number to be l ₂The time corresponding target velocity v ₂With the range walk number takes place is l ₁The time corresponding target velocity v ₁Difference as speed search step delta v;

Be step-length 7c), obtain 0≤v≤v with Δ v _MaxAll speed v in this scope, and the range walk of computing velocity target echo envelope when being v counts k=(p+1) * round (2v/ (cPRF) Δ fM), c representes the light velocity, Δ f representes the radar emission signal bandwidth;

The range walk of target echo envelope is counted k when 7d) being v according to speed, obtains the umber of pulse w in the same range unit _k=M/k, M indicating impulse number.

Step 8 is to echo data

i=1 after inserting in the time domain ... N carries out ring shift:

Umber of pulse w when at first, being v in the same range unit with the target velocity _kBe the segment length, M pulse is divided into the k group;

Then, the k group data after dividing are carried out successively the ring shift of 0～k-1 position along the distance dimension.

Step 9; Echo data after the ring shift is carried out non-coherent accumulation; Be about to mould value addition i=1 in all pulse respective distances unit of the data after the N group ring shift ... N; Accomplish the accumulation of non-coherent, N organized non-coherent accumulation and can a peak value occur at a certain range unit this moment.

Step 10, target velocity is estimated.

10a) will own [n _Min, n _Max] N that obtains after the fuzzy compensation factors organizes non-coherent accumulation

I=1 ... N compares, and selects the estimated value of the maximum accumulation corresponding fuzzy factor of peak value as the fuzzy factor of target

And get the corresponding speed of this peak-peak as objective fuzzy after the estimated value of speed Calculate the estimated value of target initial velocity

$\hat{v}=\frac{\mathrm{\λ}(\widehat{f_{d0}}+\widehat{n_k}\mathrm{PRF})}{2},$

In the formula; The estimated value of the Doppler frequency behind

expression target generation velocity ambiguity; λ representes radar wavelength,

estimated value of the fuzzy factor of expression;

10b) with fuzzy factor estimates

corresponding fuzzy compensation pulse-echo data recorded as

Step 11, the echo data

to broad sense keystone conversion and compensating for doppler after fuzzy carries out velocity compensation.

After 11a) also compensating for doppler blurs to the bending of echo data correction distance, by pulse echo data z ' (f, τ _m) in the target echo expression can find out that there is linear coupling in its second exponential term speed with the slow time, for eliminating the influence that this coupling pulsed energy accumulation brings, be similar to Wherein o () expression high-order is infinitely small, and the desin speed penalty function is:

$P(f,{\mathrm{\τ}}_m;{\hat{f}}_{d0})=\exp \left(j\frac{\mathrm{\πf}}{f_c}{\hat{f}}_{d0}{\mathrm{\τ}}_m\right),$

In the formula,

Expression velocity compensation function,

The fuzzy back of expression target is the estimated value of Doppler frequency just, and f representes frequency of distance, τ _mIt is the slow time after the variable replacement;

11b) fall the exponential term that frequency of distance and doppler velocity in the pulse echo data are coupled with velocity compensation function

compensation, the pulse echo data after the velocity compensation are designated as

11c) use the velocity compensation function

To target echo signal s ₅(f, τ _m) carry out velocity compensation, obtain the target echo signal s after the velocity compensation ₆(f, τ _m), be expressed as:

$s_6(f,{\mathrm{\τ}}_m)=A^{\′}\mathrm{rect}\left(\frac{f}{\mathrm{\Δf}}\right)\exp (-j2\mathrm{\πf}(\frac{{2R}_0}{c}+\frac{f_d}{\mathrm{\γ}}))\exp (-j2{\mathrm{\πf}}_{d0}{\mathrm{\τ}}_m)\exp \left({-\mathrm{j\π\γ}}_a{\mathrm{\τ}}_m^2\right),$

In the formula, the echo strength of A ' expression target, Δ f is the radar emission signal bandwidth, γ _aBe doppler frequency rate,

Be the Doppler frequency of target, λ is a radar wavelength, f _D0Doppler frequency after expression is fuzzy, R ₀Be target initial time distance, v is a target velocity, and a is an aimed acceleration, τ _mBe the slow time after the variable replacement, f _cBe radar emission signal carrier frequency, c is the light velocity;

11d) the pulse echo data after the velocity compensation

are distance dimension IFFT; Convert the signal into apart from time domain; Obtain the distance of pulse echo-slow time domain data, be designated as

wherein IFFT represent inverse fast Fourier transform;

11e) to the target echo signal s after the velocity compensation ₆(f, τ _m) do the distance-slow time-domain signal of the target echo that distance dimension IFFT obtains

Be expressed as:

$s_7(\hat{t},{\mathrm{\τ}}_m)=A^{\′\′}\sin c\left(\mathrm{\Δf}\right[\hat{t}-(\frac{f_d}{\mathrm{\γ}}+\frac{{2R}_0}{c})\left]\right)\exp (-j2{\mathrm{\πf}}_{d0}{\mathrm{\τ}}_m)\exp \left({-\mathrm{j\π\γ}}_a{\mathrm{\τ}}_m^2\right),$

" echo strength of target behind the IFFT is done in expression to target echo in the formula, A.

Step 12 is with Dechirp method estimating target motion acceleration.

The concrete realization of this step: the described Dechirp method of list of references " wide and narrow strip Radar Targets'Detection and imaging technique research ";

carries out the estimation of doppler frequency rate to the pulse echo data after the velocity compensation, and the estimated value of doppler frequency rate is designated as

Step 13 utilizes the estimated value

of doppler frequency rate to calculate the estimated value

of target travel acceleration

$\hat{a}=\frac{\mathrm{\λ}\widehat{{\mathrm{\γ}}_a}}{2},$

In the formula; The estimated value of

expression doppler frequency rate, λ representes radar wavelength.

Step 14 compensates the slow time dimension quadratic term of the echo data after the velocity compensation.

14a) distance of the echo signal echo the pulse echo after velocity compensation-slow time domain expression

can be found out; Also there is the quadratic phase item in pulse echo on slow time dimension; For the energy that makes echo can effectively accumulate, carry out the compensation of slow time dimension quadratic term with the data

of following formula after to velocity compensation:

$Q({\mathrm{\τ}}_m;{\widehat{\mathrm{\γ}}}_a)=\exp \left(\mathrm{j\π}{\widehat{\mathrm{\γ}}}_a{\mathrm{\τ}}_m^2\right),$

In the formula,

The penalty function of representing slow time dimension quadratic phase item, τ _mBe the slow time after the variable replacement,

The estimated value of expression doppler frequency rate;

14b) the pulse echo data after the slow time dimension quadratic term compensation are designated as

14c) with the function

on the target echo signal

for slow time-dimensional quadratic term compensation target echo signal obtained after

be expressed as:

$s_8(\hat{t},{\mathrm{\τ}}_m)=A^{\′\′}\sin c\left(\mathrm{\Δf}\right[\hat{t}-(\frac{f_d}{\mathrm{\γ}}+\frac{{2R}_0}{c})\left]\right)\exp (-j2\mathrm{\π}{f}_{d0}{\mathrm{\π}}_m)$

，

In the formula, A " echo strength of expression target,

Be the fast time, τ _mBe the slow time after the conversion, Δ f is the radar emission signal bandwidth,

Be the Doppler frequency of target, λ is a radar wavelength, f _D0Doppler frequency after expression is fuzzy, R ₀Be target initial time distance, v is a target velocity, τ _mBe the slow time after the variable replacement, c is the light velocity.

Step 15, the echo data after the compensation of slow time dimension quadratic term are done the coherent accumulation.

15a) after paired pulses echo data

carries out broad sense keystone conversion, velocity ambiguity compensation, velocity compensation and slow time dimension quadratic term compensation successively; The pulse echo data

that obtain are done the accumulation of multiple-pulse coherent, and the peak value of coherent accumulation is detected target;

15b) target echo signal

is carried out the coherent accumulation, the expression that obtains detected echo signal is:

$s_9(\hat{t},f_{\mathrm{\τ}})=A^{\′\′}\sin c\left(\mathrm{\Δf}\right[\hat{t}-(\frac{f_d}{\mathrm{\γ}}+\frac{{2R}_0}{c})\left]\right)\sin c\left(T(f_{\mathrm{\τ}}-f_{d0})\right),$

In the formula, A " echo strength of expression target,

Be the fast time, f _τBe with τ _mBe the frequency after the variable FFT conversion, FFT representes Fast Fourier Transform (FFT), and γ representes the frequency modulation rate, and Δ f is the radar emission signal bandwidth,

Be the Doppler frequency of target, λ is a radar wavelength, and T is coherent integration time, f _D0Doppler frequency after expression is fuzzy, R ₀Be target initial time distance, c is the light velocity.

Effect of the present invention further specifies through following emulation contrast test:

1. experiment scene:

Experimental data comprises with the white Gaussian noise of science software for calculation matlab R2008a emulation generation and the radar return of the high accelerated motion target of high speed; The target number is 1; The initial distance of the relative radar of target is 900 meters, and target radial speed is 3400m/s, and the target radial acceleration is 200m/s ², the radar emission carrier frequency is 1GHz, and range resolution is 2 meters, and radar pulse repetition frequency is 500Hz, and a coherent comprises 100 pulses in integration time, and signal to noise ratio (S/N ratio) is-10dB.

2. emulation content:

Utilize experimental data; Carry out computer simulation experiment; Provide testing result such as Fig. 2, Fig. 3, shown in Figure 4 of conventional sense method, optimum detection methodology and detection method according to the invention respectively; Wherein Fig. 2 is for adopting the testing result of conventional sense method, and Fig. 3 is for adopting the testing result of optimum detection methodology, and Fig. 4 is for adopting the testing result of the method for the invention.

The conventional sense method is meant that the paired pulses echo data directly is slow time dimension FFT; And optimum detection methodology is meant the paired pulses echo range curvature and the range walk of pulse echo of having carried out compensation of broad sense keystone conversion, velocity ambiguity and velocity compensation post-equalization, but the slow time dimension FFT result of pulse echo who does not carry out slow time dimension quadratic term compensation.

3. analysis of simulation result:

As can beappreciated from fig. 2; When utilizing the conventional sense method to detect,, can cause the range walk and the bending of pulse echo because target is the high accelerated motion of high speed; So the paired pulses echo data can't accumulate out energy peak after directly adopting slow time dimension FFT, thereby can't detect target.

As can beappreciated from fig. 3; When utilizing optimum detection methodology to detect; Though proofreaied and correct the range curvature and the range walk of pulse echo; But do not carry out the compensation of slow time dimension quadratic phase item, thereby make target energy on slow time dimension, still disperse can't energy accumulation still can't be detected target.

As can beappreciated from fig. 4; After utilizing the method for the invention; Be after the paired pulses echo data compensates through broad sense keystone conversion, velocity ambiguity compensation, velocity compensation, slow time dimension quadratic term; The peak value of echo envelope all has been corrected to same range unit, thereby the echoed signal that is corrected to same range unit is carried out can the target echo energy efficient being accumulated when coherent accumulates, thereby has detected target.

In sum, when the high acceleration of high speed target was detected, the inventive method obviously was superior to conventional sense method and optimum detection methodology.

Claims (8)

1. the radar target detection method based on broad sense keystone conversion and the accumulation of non-coherent comprises the steps:

1) approximate model and the noise model with the high accelerated motion target of radar high speed is expressed as respectively And d (l, t _m);

2), obtain the radar pulse echo according to target approximate model and noise model:

And paired pulses echo

With the fast time

Be FFT for variable and transform to the frequency of distance territory, obtain frequency domain data z (f, the t of echo apart from dimension _m), wherein f representes frequency of distance;

3) will be apart from frequency domain data z (f, the t of dimension _m) do the frequency domain pulse compression along the distance dimension, the data after the pulse compression are designated as z ' (f, t _m), and to the data z ' after this pulse compression (f, t _m) in slow time variable t _mWith new time variable τ _mReplace, the variable alternate form does

The data that obtain after the variable replacement are designated as z ' (f, τ _m);

4) setting fuzzy factor range is [n _Min, n _Max], n wherein _MinMinimum, n _MaxMaximum, N altogether, and all be positive integer, with data z ' (f, the τ after the fuzzy factor pair variable replacement in this scope _m) carrying out fuzzy compensation, the echo data after the compensation is designated as z ' _i(f, τ _m), i=1 ... N;

5) to the echo frequency domain data z ' behind the fuzzy compensation _i(f, τ _m), i=1 ... N carries out interior the inserting of time domain that p is ordered in each range unit, and the data after inserting in the time domain are designated as

I=1 ... N;

6) utilize data after inserting in the time domain, the echo envelope range walk is counted the umber of pulse w in k and the same range unit when calculating target velocity and being v _k

7) according to the target friction speed next time the pitch of waves from number k and the same range unit umber of pulse w of walking about _kDifference, the data after inserting in the time domain are carried out ring shift, and the group of the N after ring shift echo data are carried out non-coherent accumulation, obtain N and organize non-coherent accumulation, be designated as

I=1 ... N, wherein || expression be modulo operation;

8) N is organized non-coherent accumulation

I=1 ... N compares, and getting and wherein accumulating the maximum factor of corresponding fuzzy as a result of peak value is the velocity ambiguity factor of n of target _kEstimated value, be designated as

And the corresponding speed of the accumulation peak value of getting this maximum is fuzzy back target initial velocity v ₀Estimated value, be designated as

9) utilize the objective fuzzy obtain after initial velocity estimated value with the target initial velocity estimated value

that estimation obtains the echo frequency numeric field data

corresponding with fuzzy factor estimated value carried out velocity compensation then with the estimated value

that fuzzy factor estimated value

is calculated the target initial velocity; Echo data after will compensating again transforms to apart from time domain, is designated as

apart from time domain data after the conversion

10) to conversion later apart from time domain data Carry out the search of frequency modulation rate with the method for Dechirp, obtain frequency modulation rate γ _aEstimated value, be designated as

And then obtained the estimated value of target travel acceleration

11) with the estimated value

of the aimed acceleration that obtains the data after the velocity compensation

are carried out the compensation of slow time dimension quadratic phase item; And the data after the compensation are done the coherent accumulation of slow time dimension, the peak value of coherent accumulation is the target of detection.

2. method according to claim 1, wherein step 3) is described will be apart from frequency domain data z (f, the t of dimension _m) do the frequency domain pulse compression along the distance dimension, carry out through following formula:

$H\left(\hat{t}\right)=\mathrm{rect}\left(\frac{\hat{t}}{T_p}\right)\exp (-\mathrm{j\π\γ}{\hat{t}}^2),$

In the formula,

The indicating impulse compression function,

Be the fast time, T _pBe pulsewidth, γ is the frequency modulation rate.

3. method according to claim 1, the data after wherein the data after one group of fuzzy factor pair variable replacement of the described usefulness of step 4) are replaced variable are carried out fuzzy compensation, utilize following formula to carry out:

$G(f,{\mathrm{\τ}}_m;n_k)=\exp \left(j\frac{2\mathrm{\π}{n}_{k}f}{f_c}\sqrt{\frac{f_c}{f+f_c}}{\mathrm{PRF\τ}}_m\right),$

In the formula, n _kThe fuzzy factor of expression, τ _mBe the slow time after variable changes, f representes frequency of distance, f _cBe radar emission signal carrier frequency, PRF is the repetition frequency of radar emission signal.

4. the umber of pulse in the method according to claim 1, wherein step 6) is described when calculating target velocity and being v echo envelope range walk number and same range unit, carry out as follows:

6a) the fuzzyyest speed of calculating target

According to the fuzzyyest speed v that obtains _Max,

Calculating target echo envelope range walk number is l=(p+1) * round (2v _Maxf _s/ cPRF) with same range unit in umber of pulse w _l=M/l, wherein PRF representes the radar transmitted pulse repetition frequency, and λ representes radar wavelength, and what round represented is the operation that rounds that rounds up, f _sBe signal sampling frequency, p=1,2,3;

6b) count the umber of pulse w in l and the same range unit according to target echo envelope range walk _l, confirm speed search step delta v:

At first, get any two adjacent value l in the several 0～l-1 scopes of range walk ₁And l ₂, l ₁＜l ₂

Secondly, calculating generation range walk number is l ₁The time corresponding target velocity

With the range walk number takes place is l ₂The time corresponding target velocity

Then, use generation range walk number to be l ₂The time corresponding target velocity v ₂With the range walk number takes place is l ₁The time corresponding target velocity v ₁Difference as speed search step delta v;

Be step-length with Δ v 6c), obtaining the target velocity scope is 0≤v≤v _MaxAll speed v in this scope, and the range walk of computing velocity target echo envelope when being v counts k=(p+1) * round (2v/ (cPRF) Δ fM), c representes the light velocity, Δ f representes the radar emission signal bandwidth;

The range walk of target echo envelope is counted k when 6d) being v according to speed, obtains the umber of pulse w in the same range unit _k=M/k, M indicating impulse number.

5. method according to claim 1; Wherein described in the step 7) according to target friction speed next time the pitch of waves from the difference of the number of walking about; Data to after inserting in the time domain are carried out ring shift; Be to N group data i=1 after inserting in the time domain ... N, all operate as follows:

Umber of pulse w when at first, being v in the same range unit with the target velocity _kBe the segment length, M pulse is divided into the k group;

Then, the k group data after dividing are carried out successively the ring shift of 0～k-1 position along the distance dimension.

6. method according to claim 1, calculate the estimated value

of target initial velocity and the estimated value

of calculating target travel acceleration in the wherein said step 8) and use computes:

$\hat{v}=\frac{\mathrm{\λ}(\widehat{f_{d0}}+{\hat{n}}_k\mathrm{PRF})}{2},$

$\hat{a}=\frac{\mathrm{\λ}\widehat{{\mathrm{\γ}}_a}}{2},$

In the formula; The estimated value of first Doppler frequency behind expression target generation velocity ambiguity; λ representes radar wavelength; The estimated value of the fuzzy factor of expression, the estimated value of expression doppler frequency rate.

7. method according to claim 1, wherein the described target initial velocity estimated value pair echo frequency numeric field data corresponding with fuzzy factor estimated value that obtains with estimation of step 8) carried out velocity compensation, utilizes following formula to carry out:

$P(f,{\mathrm{\τ}}_m;{\hat{f}}_{d0})=\exp \left(j\frac{\mathrm{\πf}}{f_c}{\hat{f}}_{d0}{\mathrm{\τ}}_m\right)$

In the formula,

Expression velocity compensation function,

The fuzzy back of expression target is the estimated value of Doppler frequency just, and f representes frequency of distance, τ _mIt is the slow time after the variable replacement.

8. according to right 1 described method, wherein the data of the estimated value of the aimed acceleration that obtains of the described usefulness of step 11) after to velocity compensation are carried out the compensation of slow time dimension quadratic phase item, utilize following formula to carry out:

$Q({\mathrm{\τ}}_m;{\widehat{\mathrm{\γ}}}_a)=\exp \left(\mathrm{j\π}{\widehat{\mathrm{\γ}}}_a{\mathrm{\τ}}_m^2\right).$

In the formula,

The penalty function of representing slow time dimension quadratic phase item, τ _mBe the slow time after the variable replacement,

The estimated value of expression doppler frequency rate.

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