CN102520395B - Clutter suppression method based on bistatic multiple-input and multiple-output radar - Google Patents

Abstract

The invention discloses a clutter suppression method based on a bistatic multiple-input and multiple-output radar, which comprises the steps of: (1) separating echo signals; (2) rotating; (3) projecting; (4) estimating a clutter covariance inverse matrix; (5) detecting a weighted vector; and (6) detecting a moving target. The clutter suppression method based on the bistatic multiple-input and multiple-output radar can be suitable for conditions that a transmitter and a receiver of a bistatic radar move, and can eliminate the distance dependence of the bistatic radar. The clutter suppression method based on the bistatic multiple-input and multiple-output radar overcomes the defect of insufficient independent identical distribution training samples for space-time adaptive processing by adopting a rotary projection method for separated coordinates of all echo data, and has the advantages of sufficient independent identical distribution training samples, and capabilities of accurately evaluating clutter characteristics and forming a deep clutter notch in an actual main clutter area through space-time adaptive filtering as well as effectively suppressing clutters.

Description

Clutter suppression method based on bistatic MIMO radar

Technical field

The invention belongs to the signal process field, further relate to a kind of clutter suppression method based on bistatic MIMO radar of airborne radar technical field.The method can be used for eliminating the Range-dependent of bistatic airborne radar ground clutter, realizes detection on a surface target.

Background technology

Bistatic airborne radar is to adopt Receiver And Transmitter system separation structure to realize.The principal feature of this structure is that because transmitter is placed in rear, receiver is placed on unmanned plane, can approach target and carry out hidden investigation.Due to the power loss of having avoided the propagation of radar electromagnetic wave round trip to bring, improved the signal to noise ratio (S/N ratio) of target.Bistatic airborne radar also helps the detection Stealthy Target.For bistatic airborne radar, the land clutter of different azimuth has corresponding Doppler frequency.This fixing filtering that the coupling orientation-Doppler's coupled relation is land clutter when empty provides the starting point of research.Filter design method during coupling a kind of empty when the space-time adaptive treatment technology is exactly empty for land clutter, it can reduce the minimum detectable speed to target greatly, improves moving-target and detects performance.The space-time adaptive treatment technology requires the training sample for self-adaptive processing to have identical spectrum when empty, and the clutter sampled data between the different distance unit meets the independent same distribution condition.And, under bistatic pattern, its geometrical configuration causes clutter non-homogeneous, make the training sample between the different distance unit no longer meet the independent same distribution condition, clutter spectrum has Range-dependent.Therefore, clutter reduction is that bistatic airborne radar detects the key issue that target faces.

In the patented technology " airborne radar clutter suppression method " (application number 200910022647.3, publication number 101561497) of Xian Electronics Science and Technology University's application, a kind of airborne radar clutter suppression method is disclosed.The prior imformation that at first the method distributes according to clutter spectrum is carried out the clutter pre-service to receiving data, bidimensional dimensionality reduction while realizing sky, reduce Clutter Degrees of Freedom, then the cascade low-rank approaches self-adaptive processing, echoed signal is carried out to repeatedly filtering and space-time two-dimensional dimensionality reduction repeatedly, realize that the clutter of signal suppresses and target detection.The deficiency that the method exists is, need the abundant independent identically distributed training sample of obedience, and in the situation that the independent same distribution lack of training samples can't accurately be estimated noise performance, can not form in actual main clutter district very dark clutter depression, thus clutter reduction effectively.

In the patent " the bistatic radar ground moving target detection method based on MIMO " (application number 201110122220) of Xian Electronics Science and Technology University's application, a kind of clutter Range-dependent removing method based on the MIMO technology is disclosed.The method utilizes MIMO technique to obtain the emission cone angle information, thereby obtain the three-dimensional clutter spectrum of emission cone angle-acceptance cone-Doppler frequency, coordinate axis projection to three-dimensional clutter spectrum along acceptance cone, obtain independent identically distributed emission cone angle-Doppler frequency two dimension clutter spectrum, then utilize space-time adaptive to process and eliminate clutter, detect target.The deficiency that the method exists is, just for transmitter, move, the situation that receiver is static, only by three-dimensional clutter spectrum is eliminated to the Range-dependent of clutter along the coordinate axis projection of acceptance cone, when radar transmitter and receiver all move, the degradation that utilizes the method to eliminate the clutter Range-dependent even lost efficacy.

Summary of the invention

The object of the invention is to overcome the deficiency of above-mentioned prior art, proposed a kind of clutter suppression method based on bistatic MIMO radar, to abandon, only utilize minority to obey the method that independent identically distributed training sample is estimated clutter covariance matrix.The method, in the situation that known transmitter and receiver speed directly are rotated the array element territory coordinate of signal, can obtain independent identically distributed clutter data after new coordinate projection.

Realize that basic ideas of the present invention are, at first echo data is sampled and matched filtering, separate echoed signal, obtain the sufficient statistic certificate of signal number multiplication.Then the data array element territory coordinate obtained is rotated, postrotational data, to new coordinate axis projection, are obtained to the echo data of eliminating the clutter Range-dependent.Finally utilize space-time adaptive processing method to eliminate clutter, detect moving target.

For achieving the above object, the present invention includes following steps:

(1) separate echoed signal

Sampling thief 1a) connect after each reception array element of radar receives the each pulse echo signal analog to digital conversion sampling received of array element to each, obtains the range gate sampled data of all pulse echo signals of each reception array element;

1b) complex conjugate of each range gate sampled data and all transmitted waveforms is multiplied each other respectively, obtain the echo data separated;

1c) will same pulse within a relevant processing time, the echo data that separates of same range gate forms matrix form according to the order that receives array element, obtains the reception array element territory of respective pulses and range gate-emission array element territory echo matrix;

(2) rotation

2a) utilize following formula to calculate the anglec of rotation:

$\mathrm{\ψ}=\mathrm{arc}\tan \left(\frac{v_t}{v_r}\right)$

Wherein, ψ is the anglec of rotation, and arc tan is the arctangent cp cp operation symbol, v _tfor the speed of transmitter, v _rspeed for receiver;

2b) by step 1c) the reception array element territory that obtains-emission array element territory echo matrix representation in three-dimensional system of coordinate, obtain the echo matrix that respective pulses and range gate coordinate mean;

2c) by the abscissa axis of each echo matrix and axis of ordinates dextrorotation gyration ψ, obtain abscissa value and the ordinate value of each echo matrix under new coordinate system;

The echo matrix that 2d) utilizes abscissa value under new coordinate system and ordinate value to mean coordinate carries out bilinear interpolation, obtains the rotation echo matrix of respective pulses and range gate under new coordinate system;

(3) projection

3a) select any one range gate as range gate to be detected, select arbitrarily one group of emission space frequency in the spatial dimension that can detect at radar and receive spatial frequency as intending detection position;

The cosine that the sine that 3b) will intend the emission space frequency of detection position and anglec of rotation ψ multiplies each other, receives spatial frequency and anglec of rotation ψ multiplies each other, and two product additions obtain postrotational reception spatial frequency;

The opposite number that the cosine that 3c) will intend the emission space frequency of detection position and anglec of rotation ψ multiplies each other, receives spatial frequency and anglec of rotation ψ sine multiplies each other, and two product additions obtain postrotational emission space frequency;

3d) calculate according to the following formula the weighting column vector:

$\mathrm{\&eta;}={[e^{j2\mathrm{\&pi;}{m}_0^{\&prime;}{f}_{t,I}^{\&prime;}},e^{j2\mathrm{\&pi;}{\mathrm{<figure-callout\; id="1"\; label="m"\; filenames="HSA00000593386100021.png"\; state="\{\{state\}\}">m</figure-callout>}}_1^{\&prime;}{f}_{t,I}^{\&prime;}},\&CenterDot;\&CenterDot;\&CenterDot;,e^{j2\mathrm{\&pi;}{m}_{M-1}^{\&prime;}{f}_{t,I}^{\&prime;}}]}^T$

Wherein, η is the weighting column vector, and e is natural constant, and j is that imaginary number is-1 arithmetic square root; m ₀the value that means ordinate is 0, m ' ₀expression is by ordinate value m ₀postrotational ordinate value; f _{t, I}mean to intend the emission space frequency of detection position, f ' _{t, I}mean postrotational emission space frequency; m ₁the value that means ordinate is 1, m ' ₁expression is by ordinate value m ₁postrotational ordinate value; m _m-1the value that means ordinate is M-1, m ' _m-1expression is by ordinate value m _m-1postrotational ordinate value, M is the number of emission array element; Subscript T is the transposition symbol;

3e) each rotation echo matrix and weighting column vector are multiplied each other, obtained the rotating and projection echo column vector of respective pulses and range gate;

3f) the rotating and projection echo column vector of same range gate is arranged in to row, echo vector while obtaining respective distances door empty;

(4) estimate the clutter covariance inverse matrix

4a) will be except range gate to be detected during each range gate empty echo vector and its conjugate transpose multiply each other, autocorrelation matrix while obtaining except range gate to be detected each range gate empty;

4b) will be except range gate to be detected during all range gate empty autocorrelation matrix carry out arithmetic mean, obtain the clutter covariance matrix of range gate to be detected;

4c) clutter covariance matrix is inverted, obtain the clutter covariance inverse matrix of range gate to be detected;

(5) determine weight vectors

5a) to step 3b) the postrotational reception spatial frequency that obtains, adopt space-time adaptive processing method to determine and receive steering vector;

The normalization Doppler frequency scope that 5b) radar can be detected averages division, obtains being spaced apart one group of normalization Doppler frequency of arranging from small to large of minimum distinguishable normalization Doppler frequency;

5c) to each normalization Doppler frequency, adopt space-time adaptive processing method to determine its Doppler's vector, obtain one group of Doppler's vector;

5d) receive steering vector and ask Kronecker to amass with each Doppler's vector, steering vector while obtaining empty after one group of rotating and projection;

The clutter covariance inverse matrix of steering vector and range gate to be detected during 5e) to empty after each rotating and projection, adopt the capon least variance method to determine weight vectors, obtains one group of weight vectors;

(6) detect moving target

6a) by step 3f) range gate to be detected that obtains when empty the echo vector carry out transposition, obtain a transposition vector;

6b) by transposition vector and step 5e) each weight vectors of obtaining multiplies each other respectively, obtains one group of echo data of intending clutter reduction on detection position;

6c) echo data of clutter reduction adopted to average class CFAR detection method, detect moving target.

The present invention compared with prior art has the following advantages:

First, the present invention adopts directly the whole echo datas that separate is converted to the method that obtains independent identically distributed clutter data, having overcome prior art utilizes the space-time adaptive processing to need the abundant independent identically distributed training sample of obedience, and in the situation that the independent same distribution lack of training samples, can't accurately estimate noise performance, can not form in actual main clutter district very dark clutter depression, thereby the shortcoming of clutter reduction effectively, make the present invention there is sufficient independent same distribution training sample, can accurately estimate noise performance, can form in actual main clutter district very dark clutter depression by space-time adaptive filtering, the advantage of clutter reduction effectively.

Second, the present invention is rotated projection by the echo data to receiving, having overcome prior art just moves for transmitter, the situation that receiver is static, and when radar transmitter and receiver all move, only by can't eliminate the shortcoming of clutter Range-dependent along the coordinate axis projection of acceptance cone to three-dimensional clutter spectrum, the situation that makes the present invention all move applicable to transmitter and receiver, can eliminate the Range-dependent of clutter, obtain the advantage of independent identically distributed clutter data.

The accompanying drawing explanation

Fig. 1 is process flow diagram of the present invention;

Fig. 2 is the simulated effect figure of the present invention to the clutter spectrum rotating and projection;

Fig. 3 is that the present invention exports Signal to Interference plus Noise Ratio simulated effect figure.

Embodiment

Below in conjunction with 1 pair of step of the present invention of accompanying drawing, be described in further detail.

Step 1: separate echoed signal

In example of the present invention, the bistatic radar pattern is, emission array element is arranged on transmitter, receives array element and is arranged on receiver, and be all positive side-looking.The emission array element number is 11, and receiving array element number is 11, launches battle array and receive battle array to be uniform line-array.Within the processing time of once being concerned with, each receives array element and receives 10 pulse echo data.

The sampling thief connect after each reception array element of radar receives the each pulse echo signal received of array element to each and carries out the analog to digital conversion sampling, obtains the range gate sampled data Y that each receives all pulse echo signals of array element ¹∈ C ^{24200 * 1}.The analog to digital conversion sampling number is two times of reception array number and umber of pulse product, and each receives in the each pulse echo signal received of array element 220 range gate sampled datas.Complex conjugate vector S by each range gate sampled data and transmitted waveform ^*multiply each other, obtain the echo data Y separated ²∈ C ^{266200 * 1}.Wherein, for transmitted waveform complex conjugate vector, subscript * represents conjugation,

represent the complex conjugate of the 1st emission array element transmitted waveform,

represent the complex conjugate of the 2nd emission array element transmitted waveform, the rest may be inferred,

represent the complex conjugate of the 11st emission array element transmitted waveform, subscript T is the transposition symbol.

Will same pulse within a relevant processing time, the echo data that separates of same range gate forms matrix form according to the order that receives array element, obtain the reception array element territory of respective pulses and range gate-emission array element territory echo matrix, obtain altogether 2200 and receive array element territory-emission array element territory echo matrix, matrix form is that the echo data that first is received to the array element separation comes the first row, second echo data that receives the array element separation comes the second row, and the rest may be inferred.With

mean the reception array element territory of k range gate of l pulse-emission array element territory echo matrix.Wherein, l=1,2 ..., 10, k=1,2 ..., 220.

Step 2: rotation

Utilize following formula to calculate the anglec of rotation:

$\mathrm{\&psi;}=\mathrm{arc}\tan \left(\frac{v_t}{v_r}\right)$

Wherein, ψ is the anglec of rotation, and arc tan is the arctangent cp cp operation symbol, v _tfor the speed of transmitter, v _rfor the speed of receiver, the speed v of transmitter in example of the present invention _tfor 100m/s, the speed v of receiver _rfor 100m/s.

To receive array element territory-emission array element territory echo matrix

be illustrated in three-dimensional system of coordinate, wherein, l=1,2 ..., 10, k=1,2 ... 220, obtain the echo matrix that respective pulses and range gate coordinate mean, obtain altogether the echo matrix that 2200 coordinates mean, the method of echo matrix representation in three-dimensional system of coordinate is, the abscissa axis representative receives the array element territory, and abscissa value is all integer, and scope is for subtracting 1 from 0 to receiving array element number; Axis of ordinates representative emission array element territory, ordinate value is all integer, and scope is for subtracting 1 from 0 to the emission array element number; The ordinate axle represents the numerical value in the echo matrix.

By the abscissa axis of each echo matrix and axis of ordinates dextrorotation gyration ψ, obtain abscissa value and the ordinate value of each echo matrix under new coordinate system, abscissa value and ordinate value under new coordinate system can be calculated with following formula:

$\left[\begin{array}{c}{n}^{\&prime;}\\ m^{\&prime;}\end{array}\right]=\left[\begin{array}{cc}\cos \mathrm{\&psi;}& \sin \mathrm{\&psi;}\\ -\sin \mathrm{\&psi;}& \cos \mathrm{\&psi;}\end{array}\right]\left[\begin{array}{c}n\\ m\end{array}\right]$

Wherein, n ' is the horizontal ordinate under postrotational new coordinate system, n '=n ' ₀, n ' ₁... n ' ₁₀, n ₀the value that means horizontal ordinate is 0, n ' ₀expression is by abscissa value n ₀postrotational abscissa value, n ₁the value that means horizontal ordinate is 1, n ' ₁expression is by abscissa value n ₁postrotational abscissa value, the rest may be inferred, n ₁₀the value that means horizontal ordinate is 10, n ' ₁₀expression is by abscissa value n ₁₀postrotational abscissa value.M ' is the ordinate under postrotational new coordinate system, m '=m ' ₀, m ' ₁... m ' ₁₀, m ₀the value that means ordinate is 0, m ' ₀expression is by ordinate value m ₀postrotational ordinate value, m ₁the value that means ordinate is 1, m ' ₁expression is by ordinate value m ₁postrotational ordinate value, the rest may be inferred, m ₁₀the value that means ordinate is 10, m ' ₁₀expression is by ordinate value m ₁₀postrotational ordinate value.The cosine that cos ψ is angle ψ, the sine that sin ψ is angle ψ, n means the horizontal ordinate in echo matrix array elements territory, n=0,1 ... 10.M means the ordinate in echo matrix array elements territory, m=0, and 1 ... 10.

The echo matrix that utilizes abscissa value under new coordinate system and ordinate value to mean coordinate carries out bilinear interpolation, obtain the rotation echo matrix of respective pulses and range gate under new coordinate system, obtain altogether 2200 rotation echo matrixes, the order of bilinear interpolation is, first carry out the interpolation on the abscissa axis direction, then carry out the interpolation on the axis of ordinates direction.With

the rotation echo matrix that means k range gate of l pulse, wherein, l=1,2 ..., 10, k=1,2 ..., 220.

Step 3: projection

In example of the present invention, select the 20th range gate as range gate to be detected, intend the emission space frequency f of detection position _{t, I}=0, receive spatial frequency f _{r, I}=0.106.Postrotational emission space frequency is f ' _{t, I}=f _{t, I}cos ψ-f _{r, I}sin ψ, postrotational reception spatial frequency is f ' _{r, I}=f _{t, I}sin ψ+f _{r, I}cos ψ, wherein, the cosine that cos ψ is angle ψ, the sine that sin ψ is angle ψ.

Calculate according to the following formula the weighting column vector:

$\mathrm{\&eta;}={[e^{j2\mathrm{\&pi;}{m}_0^{\&prime;}{f}_{t,I}^{\&prime;}},e^{j2\mathrm{\&pi;}{\mathrm{<figure-callout\; id="1"\; label="m"\; filenames="HSA00000593386100021.png"\; state="\{\{state\}\}">m</figure-callout>}}_1^{\&prime;}{f}_{t,I}^{\&prime;}},\&CenterDot;\&CenterDot;\&CenterDot;,e^{j2\mathrm{\&pi;}{m}_{10}^{\&prime;}{f}_{t,I}^{\&prime;}}]}^T$

Wherein, η is the weighting column vector, and e is natural constant, and j is that imaginary number is-1 arithmetic square root; m ₀the value that means ordinate is 0, m ' ₀expression is by ordinate value m ₀postrotational ordinate value; f _{t, I}mean to intend the emission space frequency of detection position, f ' _{t, I}mean postrotational emission space frequency; m ₁the value that means ordinate is 1, m ' ₁expression is by ordinate value m ₁postrotational ordinate value; m ₁₀the value that means ordinate is 10, m ' ₁₀expression is by ordinate value m ₁₀postrotational ordinate value; Subscript T is the transposition symbol.

To rotate the echo matrix with the weighting column vector, η is multiplied each other, and obtains the echo column vector of respective pulses and range gate rotating and projection, obtains altogether the echo column vector of 2200 rotating and projections.With

the echo column vector that means k range gate rotating and projection of l pulse.Wherein, l=1,2 ..., 10, k=1,2 ..., 220.

The echo column vector of same range gate is arranged in to row, echo vector while obtaining respective distances door empty.The method that the echo column vector is arranged in row is, the echo column vector of same first pulse of range gate is formed a line, again the echo column vector of second pulse of same range gate is come below the echo column vector of first pulse, the rest may be inferred, by the echo column vector of all pulses of the same range gate echo vector while forming this range gate empty that forms a line, echo column vector to all range gate all carries out aforesaid operations, echo vector while obtaining all range gate empty.With

echo vector while meaning k range gate empty, wherein, k=1,2 ..., 220.

Step 4: estimate the clutter covariance inverse matrix

Will be except the 20th range gate during each range gate empty echo vector and its conjugate transpose multiply each other, autocorrelation matrix while obtaining except the 20th range gate each range gate empty.With

autocorrelation matrix while meaning k range gate empty,

k=1,2 ..., 220, k ≠ 20, subscript H is the conjugate transpose symbol.

Will be except the 20th range gate during all range gate empty autocorrelation matrix carry out arithmetic mean, obtain the clutter covariance matrix of the 20th range gate estimating.With X ∈ C ^{110 * 110}the clutter covariance matrix that means the 20th range gate of estimation, clutter covariance matrix is inverted, obtain the clutter covariance inverse matrix X of the 20th range gate ^-1∈ C ^{110 * 110}.

Step 5: determine weight vectors

To postrotational reception spatial frequency f ' _{r, I}, adopt space-time adaptive processing method to determine and receive steering vector A ∈ C ^{11 * 1}, receiving steering vector and refer to, signal arrives the vector that the phase differential that respectively receives array element forms.In example of the present invention

subscript T is the transposition symbol.

The normalization Doppler frequency scope [0.5,0.5] that radar can be detected averages division, obtains being spaced apart minimum distinguishable normalization Doppler frequency f _dminone group of normalization Doppler frequency of arranging from small to large of=0.01, F _d=[f _d1, f _d2..., f _d100], the maximum detection range that is about to radar is divided into 100 parts, and adjacent two normalization Doppler frequencies differ f _dmin=0.01.To each normalization Doppler frequency, adopt space-time adaptive processing method to determine its Doppler's vector, obtain 100 Doppler's vectors, Doppler's vector refers to the vector that Doppler frequency forms at the interpulse phase differential caused.Use B _q∈ C ^{10 * 1}expression is by q normalization Doppler frequency f _dqdefinite Doppler's vector, wherein

q=1,2 ... 100, f _dq=f _d1, f _d2... f _d100, subscript T is the transposition symbol.

Receive steering vector A ∈ C ^{11 * 1}with each Doppler's vector B _q∈ C ^{10 * 1}ask Kronecker long-pending, steering vector while obtaining empty after one group of rotating and projection.Use g _q∈ C ^{110 * 1}mean to receive steering vector and q Doppler's vector B _qsteering vector during empty after the rotating and projection of trying to achieve,

wherein, q=1,2 ... 100,

mean that Kronecker is long-pending.

The clutter covariance inverse matrix of steering vector and the 20th range gate during to empty after each rotating and projection, adopt the capon least variance method to determine weight vectors, obtain one group of weight vectors, the capon least variance method is, the conjugate transpose vector of steering vector during by sky, clutter covariance inverse matrix and when empty the steering vector three multiply each other, determine a scalar, then by the inverse of this scalar, clutter covariance inverse matrix and when empty the steering vector three multiply each other, obtain weight vectors.Use W _q∈ C ^{110 * 1}mean q weight vectors, W _q=μ X ^-1g _q, wherein, μ is scalar,

steering vector g while being q sky _q∈ C ^{110 * 1}the conjugate transpose vector, subscript H is the conjugate transpose symbol, q=1,2 ... 100, X ^-1∈ C ^{110 * 110}it is the clutter covariance inverse matrix of the 20th range gate.

Step 6: detect moving target

Echo vector when the 20th range gate is empty carry out transposition, obtain a transposition vector by this transposition vector

with weight vectors W _qmultiply each other, obtain intending the echo data of clutter reduction on detection position

q=1,2 ... 100.Echo data Z to clutter reduction _qadopt average class CFAR detection method, detect moving target.

Below in conjunction with accompanying drawing 2,3 pairs of effects of the present invention of accompanying drawing, be described further.

The simulation parameter of accompanying drawing 2, accompanying drawing 3 arranges as follows: emission array element number 11, receive array element number 11, an interior umber of pulse 10 of relevant processing time, carrier frequency 1.24GHZ, pulse repetition rate 2000HZ, base length 100km, receiver height 5000m, receiver speed 100m/s, the receiver heading is with respect to 0 ° of the angle of transverse axis, transmitter height 10000m, transmitter speed 100m/s, the transmitter heading, with respect to 90 ° of the angles of transverse axis, is intended detection position emission space frequency f _{t, I}=0, intend detection position and receive spatial frequency f _{r, I}=0.106, each transmitter unit emissive power 1, the noise power 0.1 of receiving element.

Fig. 2 is the simulated effect figure of the present invention to the clutter spectrum rotating and projection.Wherein, Fig. 2 (a) does not adopt three-dimensional clutter spectrum of the present invention to project to the clutter spectrogram on two-dimensional quadrature plane, and Fig. 2 (b) utilizes the present invention by the clutter spectrogram obtained after three-dimensional clutter spectrum rotating and projection.

In Fig. 2 (a), horizontal ordinate means the normalization Doppler frequency, ordinate means the reception spatial frequency after projection, in the clutter spectrogram, the corresponding a plurality of reception spatial frequencys of normalization Doppler frequency, one receives the corresponding a plurality of normalization Doppler frequencies of spatial frequency, be the clutter spectrum difference of different distance, clutter spectrum has Range-dependent.In Fig. 2 (b), horizontal ordinate is the reception spatial frequency f ' after rotating and projection _r, its expression formula is f ' _r=f _rcos ψ+f _tsin ψ, wherein, f _rfor the reception spatial frequency before the clutter spectrum rotation, the cosine that cos ψ is anglec of rotation ψ, f _tfor the emission space frequency before the clutter spectrum rotation, the sine that sin ψ is anglec of rotation ψ; Ordinate is normalization Doppler frequency f _d, clutter spectrum is straight line, and the clutter spectral line is as shown in the spectral line that label in Fig. 2 (b) is 1, and after rotating and projection, the clutter spectrum of different distance, on the same straight line, has been eliminated the Range-dependent characteristic of clutter as seen, and clutter spectrum meets the independent same distribution condition.

Fig. 3 is that the present invention exports Signal to Interference plus Noise Ratio simulated effect figure.In figure, dot-and-dash line is the output Signal to Interference plus Noise Ratio figure that directly uses space-time adaptive processing method, and solid line is to use output Signal to Interference plus Noise Ratio figure of the present invention, and dotted line is the output Signal to Interference plus Noise Ratio figure that uses joint space-time interpolation STINT method.

By solid line in Fig. 3 and dashdotted contrast, it is visible in the echo data to receiving is directly applied the dot-dash line chart of space-time adaptive treatment S TAP method, owing to meeting, independent identically distributed training sample is insufficient, can not accurately estimate clutter covariance matrix by it, space-time adaptive filtering can not form in actual main clutter district very dark clutter depression, so the output Signal to Interference plus Noise Ratio is not high enough, detect poor performance.After the method that adopts the present invention to propose, the output Signal to Interference plus Noise Ratio, in the worst case than the high 30dB of direct application space-time adaptive treatment S TAP method, detects performance and has greatly improved.

Contrast by solid line in Fig. 3 and dotted line, output Signal to Interference plus Noise Ratio of the present invention is with respect to the low 11dB of output Signal to Interference plus Noise Ratio of joint space-time interpolating method, but it should be noted that application joint space-time interpolating method STINT method need to obtain the space-Doppler frequency pair of bistatic clutter position, it changes along with the variation of bistatic radar geometrical configuration, and the geometrical configuration of bistatic radar changes along with the motion of Texas tower, so the space-Doppler frequency of the bistatic clutter position obtained is to very complicated.Yet the present invention only need calculate anglec of rotation ψ according to the speed of bistatic radar transmitter and receiver, so that method proposed by the invention should use than joint space-time interpolating method STINT is easier.

Claims (8)

1. the clutter suppression method based on bistatic MIMO radar, comprise the steps:

(1) separate echoed signal

Sampling thief 1a) connect after each reception array element of radar receives the each pulse echo signal analog to digital conversion sampling received of array element to each, obtains the range gate sampled data of all pulse echo signals of each reception array element;

1b) complex conjugate of each range gate sampled data and all transmitted waveforms is multiplied each other respectively, obtain the echo data separated;

1c) will same pulse within a relevant processing time, the echo data that separates of same range gate forms matrix form according to the order that receives array element, obtains the reception array element territory of respective pulses and range gate-emission array element territory echo matrix;

(2) rotation

2a) utilize following formula to calculate the anglec of rotation:

$\mathrm{\&psi;}=\arctan \left(\frac{v_t}{v_r}\right)$

Wherein, ψ is the anglec of rotation, and arctan is the arctangent cp cp operation symbol, v _tfor the speed of transmitter, v _rspeed for receiver;

2b) by step 1c) the reception array element territory that obtains-emission array element territory echo matrix representation in three-dimensional system of coordinate, obtain the echo matrix that respective pulses and range gate coordinate mean; Described by the echo matrix representation, the method in three-dimensional system of coordinate is, the abscissa axis representative receives the array element territory, and abscissa value is all integer, and scope is for subtracting 1 from 0 to receiving array element number; Axis of ordinates representative emission array element territory, ordinate value is all integer, and scope is for subtracting 1 from 0 to the emission array element number; The ordinate axle represents the numerical value in the echo matrix;

2c) by the abscissa axis of each echo matrix and axis of ordinates dextrorotation gyration ψ, obtain abscissa value and the ordinate value of each echo matrix under new coordinate system;

The echo matrix that 2d) utilizes abscissa value under new coordinate system and ordinate value to mean coordinate carries out bilinear interpolation, obtains the rotation echo matrix of respective pulses and range gate under new coordinate system;

(3) projection

3a) select any one range gate as range gate to be detected, select arbitrarily one group of emission space frequency in the spatial dimension that can detect at radar and receive spatial frequency as intending detection position;

The cosine that the sine that 3b) will intend the emission space frequency of detection position and anglec of rotation ψ multiplies each other, receives spatial frequency and anglec of rotation ψ multiplies each other, and two product additions obtain postrotational reception spatial frequency;

The opposite number that the cosine that 3c) will intend the emission space frequency of detection position and anglec of rotation ψ multiplies each other, receives spatial frequency and anglec of rotation ψ sine multiplies each other, and two product additions obtain postrotational emission space frequency;

3d) calculate according to the following formula the weighting column vector:

$\mathrm{\&eta;}={[e^{j2\mathrm{\&pi;}{m}_0^{\&prime;}{f}_{t,I}^{\&prime;}},e^{j2\mathrm{\&pi;}{m}_1^{\&prime;}{f}_{t,I}^{\&prime;}},\&CenterDot;\&CenterDot;\&CenterDot;,e^{j2\mathrm{\&pi;}{m}_{M-1}^{\&prime;}{f}_{t,I}^{\&prime;}}]}^T$

Wherein, η is the weighting column vector, and e is natural constant, and j is that imaginary number is-1 arithmetic square root; m ₀the value that means ordinate is 0, m ' ₀expression is by ordinate value m ₀postrotational ordinate value; f _{t, I}mean to intend the emission space frequency of detection position, f ' _{t, I}mean postrotational emission space frequency; m ₁the value that means ordinate is 1, m ' ₁expression is by ordinate value m ₁postrotational ordinate value; m _m-1the value that means ordinate is M-1, m _m-1expression is by ordinate value m _m-1postrotational ordinate value, M is the number of emission array element; Subscript T is the transposition symbol;

3e) each rotation echo matrix and weighting column vector are multiplied each other, obtained the rotating and projection echo column vector of respective pulses and range gate;

3f) the rotating and projection echo column vector of same range gate is arranged in to row, echo vector while obtaining respective distances door empty;

(4) estimate the clutter covariance inverse matrix

4a) will be except range gate to be detected during each range gate empty echo vector and its conjugate transpose multiply each other, autocorrelation matrix while obtaining except range gate to be detected each range gate empty;

4b) will be except range gate to be detected during all range gate empty autocorrelation matrix carry out arithmetic mean, obtain the clutter covariance matrix of range gate to be detected;

4c) clutter covariance matrix is inverted, obtain the clutter covariance inverse matrix of range gate to be detected;

(5) determine weight vectors

5a) to step 3b) the postrotational reception spatial frequency that obtains, adopt space-time adaptive processing method to determine and receive steering vector;

The normalization Doppler frequency scope that 5b) radar can be detected averages division, obtains being spaced apart one group of normalization Doppler frequency of arranging from small to large of minimum distinguishable normalization Doppler frequency;

5c) to each normalization Doppler frequency, adopt space-time adaptive processing method to determine its Doppler's vector, obtain one group of Doppler's vector;

5d) receive steering vector and ask Kronecker to amass with each Doppler's vector, steering vector while obtaining empty after one group of rotating and projection;

The clutter covariance inverse matrix of steering vector and range gate to be detected during 5e) to empty after each rotating and projection, adopt the capon least variance method to determine weight vectors, obtains one group of weight vectors;

(6) detect moving target

6a) by step 3f) range gate to be detected that obtains when empty the echo vector carry out transposition, obtain a transposition vector;

6b) by transposition vector and step 5e) each weight vectors of obtaining multiplies each other respectively, obtains one group of echo data of intending clutter reduction on detection position;

6c) echo data of clutter reduction adopted to average class CFAR detection method, detect moving target.

2. the clutter suppression method based on bistatic MIMO radar according to claim 1, is characterized in that step 1a) described analog to digital conversion sampling number is for receiving array number and umber of pulse product two times.

3. the clutter suppression method based on bistatic MIMO radar according to claim 1, it is characterized in that, step 1c) described matrix form is that the echo data that first is received to the array element separation comes the first row, second echo data that receives the array element separation comes the second row, and the rest may be inferred.

4. the clutter suppression method based on bistatic MIMO radar according to claim 1, it is characterized in that, step 2d) order of described bilinear interpolation is, first carries out the interpolation on the abscissa axis direction, then carries out the interpolation on the axis of ordinates direction.

5. the clutter suppression method based on bistatic MIMO radar according to claim 1, it is characterized in that, step 3f) method that described echo column vector is arranged in row is, the echo column vector of same first pulse of range gate is formed a line, again the echo column vector of second pulse of same range gate is come below the echo column vector of first pulse, the rest may be inferred, by the echo column vector of all pulses of the same range gate echo vector while forming this range gate empty that forms a line, echo column vector to all range gate all carries out aforesaid operations, echo vector while obtaining all range gate empty.

6. the clutter suppression method based on bistatic MIMO radar according to claim 1, is characterized in that step 5a) described reception steering vector refers to, signal arrives the vector that the phase differential that respectively receives array element forms.

7. the clutter suppression method based on bistatic MIMO radar according to claim 1, is characterized in that step 5c) described Doppler's vector refers to, the vector that Doppler frequency forms at the interpulse phase differential caused.

8. the clutter suppression method based on bistatic MIMO radar according to claim 1, it is characterized in that, step 5e) described capon least variance method is, the conjugate transpose vector of steering vector during by sky, clutter covariance inverse matrix and when empty the steering vector three multiply each other, determine a scalar, during again by the inverse of this scalar, clutter covariance inverse matrix and sky, the steering vector three is multiplied each other, and obtains weight vectors.

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