CN101533092A - Method for synchronously inhibiting radar clutter and multiple interferences based on power distinction - Google Patents

Abstract

The invention discloses a method for synchronously inhibiting radar clutter and multiple interferences based on power distinction, and is suitable for a signal processing system of sky-wave over-the-horizon radar. The method realizes the separation of strong clutter, interferences and target signal using the power difference among the clutter, interferences and target signal, and can effectively inhibit clutter and multiple interferences including transient interference and shared-frequency asynchronous interference. The specific steps are showed in the figure 1. Compared with the prior method, the method does not need to detect and analyze the clutter and multiple interferences complicatedly, has obvious effect on the randomly varied interferences of all parameters and clutter, and has strong applicability. The invention uses the separated strong clutter as a standard signal to correct phase pollution, can realize phase correction and inhibit the clutter and interferences synchronously, and simplify the signal processing process of the sky-wave over-the-horizon radar. The invention is not limited to the sky-wave over-the-horizon radar system, can be widely applied to multiple large-scale phased array radars, and has wide application value.

Description

Radar clutter and multiple interference based on power distinction suppress method simultaneously

Technical field

A kind of clutter and the multiple interference that the present invention relates in the radar signal processing field suppress method simultaneously, be applicable to the signal processing system of sky-wave OTH radar, can be used to exist the moving object detection under asynchronous system interference, glitch, phase place pollution, the main clutter background.Simultaneously, core theory and method also can be applicable to other clutters and multiple existence and disturb in the signal processing system of controlling consumption.

Background technology

Sky-wave OTH radar utilizes ionosphere that electromagnetic reflection is realized that operating distance is far away, coverage is big, and strategic early-warning information information can be provided to the detection of the outer target of sighting distance.But because working system is special, be vulnerable to the influence of multiple interference and clutter, cause following problem: (3～30MHz), industrial noise is intensive in crowded high-frequency band for (1) system works; (2) investigative range is wide, echo signal is faint, and glitch such as thunder and lightning, meteoric trail very easily enter system, raises the doppler spectral noise floor and covers target; (3) target adopts the big coherent accumulation time in order to survey at a slow speed, during ionosphere phase perturbation non-linearization, the clutter spectrum broadening; (4) look under mode of operation is brought formidably, extra large clutter.Therefore, do not take corresponding measure, system can't operate as normal.At present, comprise in the existing interference protection measure of signal processing stage: the method filtering glitch that compensates again after adopting time domain to excavate; Utilize various phase places pollution alignment techniques to carry out phase place and separate pollution; Utilize moving object detection (MTD) technology clutter reduction etc.But they all have problems to some extent.

The time domain method of excavating is based on the glitch characteristics that only a few periods occurs on time domain and proposes.Position for detected transient is disturbed needs the ground that suppresses powerful, extra large clutter before excavating; Make the clutter spectrum broadening for fear of the sudden change of excavating place's clutter, also need after excavating the point of excavating to be made interpolation processing by the characteristic of clutter.There are problems such as glitch detection, compensating error.In addition, also have time frequency analysis to remove the glitch method, mainly utilize glitch and echo signal, the different time-frequency characteristic of clutter, it is deducted from received signal, do not have compensating error, but required calculated amount is bigger.

Present phase place is polluted alignment technique and is mainly comprised three class methods, and first kind method is polluted nonlinear phase by piecewise approximation and proofreaied and correct for linear the pollution, can not handle phase place and pollute the violent situation of disturbance; Second class methods polynomial function analog electrical absciss layer phase perturbation function, the polynomial function exponent number that is used to simulate when phase perturbation is violent can be very high, and error increases; The 3rd class methods are estimated phase perturbation with the phase gradient of the auxiliary correction signal of single-frequency, and the Bragg peak that utilizes extra large clutter usually is as this auxiliary signal, but the definite of this peak width effectively solved as yet.

The process of conventional MTD technology filtering main clutter is that directly Doppler's channel data that clutter is shared is excavated, and Doppler's port number of generally excavating is a fixed value, and this value utilizes prior imformation directly to obtain.But in real background, the shared Doppler's port number of clutter changes, and the coherent pulse number of it and radar emission, the factors such as beam position of array are relevant.The method that adopts stationary conduit to excavate can also have been rejected the target that is positioned at clutter edge in a large number when excavating clutter, be unfavorable for the detection of target at a slow speed.

In addition, sky-wave OTH radar also faces all as other interference such as frequency asynchronous interference.The opportunity that these interference occur, position etc. are random variation all, does not still have effective ways at present and is suppressed.

Summary of the invention

The objective of the invention is to solve difficulty and the problem that sky-wave OTH radar system operate as normal is faced, overcome the existing methods shortcoming and defect.Under the prerequisite that does not change system hardware structure, effectively transient suppression interference, clutter and the industrial noise that occurs at random, and finish phase place when being necessary and separate pollution.

In order to realize the foregoing invention purpose, the invention provides a kind of radar clutter and multiple interference and suppress method simultaneously based on power distinction, comprise the steps:

(1) receives that the punching press of data passages through which vital energy circulates is contracted and after wave beam forms, obtain recurrence interval data vector x _Mn, estimate its correlation matrix R:

$R=\frac{1}{\mathrm{MN}}\underset{m=1}{\overset{M}{\mathrm{\Σ}}}\underset{n=1}{\overset{N}{\mathrm{\Σ}}}{x}_{\mathrm{mn}}{x}_{\mathrm{mn}}^H$

Wherein, x _Mn=[x _Mn(1) x _Mn(2) ... x _Mn(l) ... x _Mn(L)] ^T, x _Mn(l) be the data of l recurrence interval of m range gate, a n wave beam passage, L is the recurrence interval number, and M is that range gate number, N are numbers of beams;

(2) R is carried out feature decomposition, obtain eigenvector group U by the big minispread of eigenwert;

(3) eigenvalue of maximum character pair vector is defined as strong clutter eigenvector u ₁, determine a big eigenwert number thresholding, from first big eigenwert until this thresholding, its character pair set of vectors is defined as clutter and disturbs character pair space U _C1

(4) utilize strong clutter eigenvector group, clutter and interference characteristic set of vectors to data x _MnCarry out filtering, data be divided into strong clutter, clutter and interference and three kinds of signals of target:

$x_{\mathrm{Cmn}}=u_1{u}_1^H{x}_{\mathrm{mn}}$

$x_{\mathrm{Imn}}=U_{\mathrm{CI}}{U}_{\mathrm{CI}}^H{x}_{\mathrm{mn}}$

$x_{\mathrm{Tmn}}=(I-U_{\mathrm{CI}}{U}_{\mathrm{CI}}^H)x_{\mathrm{mn}}$

Wherein, x _CmnBe strong noise signal, x _ImnBe clutter and undesired signal, x _TmnBe echo signal;

(5) utilize strong noise signal to carry out phase place and separate pollution, send subsequent treatment such as coherent accumulation, CFAR detection the data of separating after the pollution.

Correlation matrix R can be by all wave beams and range unit data x in the step (1) _Mn(m=1,2 ..., Mn=1,2 ..., N) form, also can exist the data estimation of powerful clutter range unit to form by part wave beam and part.

Big eigenwert number thresholding also adopts the priori threshold method to determine in the step (3): set different judgement thresholdings from small to large and handle respectively; When thresholding hour because interference noise is suppressed not thorough, false-alarm is more; Along with the raising of thresholding, noise jamming is inhibited, and detected target numbers will reduce gradually, when detected target numbers is stablized in the result, with corresponding threshold value as the priori threshold value in this irradiation area.The priori threshold value can obtain and store at off-line at ordinary times, directly utilizes this threshold value to distinguish the size of noise jamming feature space when handling in real time.More real-time simultaneously normalization characteristic spectrum and the expectation normalization characteristic spectrum that collects are at ordinary times revised big eigenwert thresholding when the two significant difference occurs.

Phase place is separated pollution and can also be adopted the phase gradient method in the step (5), proofreaies and correct clutter and the undesired signal x that is polluted with the phase information of strong noise signal _ImnWith echo signal x _Tmn:

Wherein, angle{} represents to get the ambiguity solution phase place of data in the bracket, and diag{} represents the diagonal matrix be made up of vector in the bracket.

The invention has the advantages that:

(1) the present invention need not glitch is detected and compensates.The present invention utilized glitch on power much larger than the characteristics of target, can easily it and echo signal be made a distinction, from original signal, deduct.Need not to analyze glitch and be present in which cycle, also need not after the cycle zero setting that artificially will have glitch, to compensate, therefore the error that does not exist compensation to bring; Also need not carry out complicated time frequency analysis.

(2) compare with the method for utilizing MTD technology clutter reduction, the present invention need not to consider definite problem of clutter port number.No matter clutter wide or narrow, be which kind of shape, inhibition degree to clutter is determined by the size of clutter power fully, have only that those power are strong, the clutter that has a strong impact on target detection is by filtering, lower-powered echo signal is then kept, and has the characteristics of " self-adaptation ".

(3) the invention solves the problem of choosing that phase place is separated Bragg peak-to-peak signal width in the pollution.The phase gradient method can be followed the tracks of the acute variation that phase place is polluted, pollute bearing calibration with respect to other phase places and have stronger applicability and correcting feature, but be subjected to the puzzlement that correction signal is selected: desirable correction signal should be a simple signal always, but how signal spectrum broadening under the phase place pollution condition determines that the broadening degree is very difficult.And the present invention leaches strong clutter according to watt level, and its width is determined automatically.

(4) the present invention's industrial noise that can suppress to occur at random need not to carry out complicated detection.The industrial noise of Chu Xianing is the problem that is effectively solved as yet in the Radar Signal Processing system at random, can only suppress the result and seriously rely on the detection effect by after the Interference Detection and in addition filtering.In order to adapt to various situations, required Interference Detection means are very complicated.The inventive method does not need any detection means, as long as jamming power greater than echo signal, just can reach the inhibition effect.

(5) the inventive method can be finished in a step needs multiple technologies to cooperate the purpose that just can reach at present, has simplified the realization complexity of prior art greatly.

Description of drawings

Fig. 1 adopts a kind of sky-wave OTH radar signal Processing of the present invention to concern process flow diagram;

Fig. 2 is one embodiment of the present invention process flow diagrams;

Embodiment

Existing signal processing theory shows, the signal coherence matrix is carried out the eigenvector that feature decomposition obtains, can be divided into mutually orthogonal signal subspace and noise subspace by character pair value size, wherein signal subspace has comprised the information of all signal manipulation vectors.And current research shows, in signal subspace inside, there is corresponding relation between eigenvector and the signal manipulation vector, character vector of signals can independently reflect the information of respective signal manipulation vector, prerequisite is that the power between the signal exists difference, and " independence " degree of this reflection is directly proportional with the signal power difference.

In the sky-wave OTH radar system, clutter power maximum, jamming power are taken second place echo signal power minimum usually.Therefore, according to clutter, interference and the signal difference on power, the character vector of signals of received signal coherence matrix can be divided into clutter, interference and character vector of signals interval.To be used respectively, suppress the mechanism that this promptly suppresses method simultaneously based on the clutter and the multiple interference of power distinction when then can reach to clutter and multiple interference.Based on the orthogonality of noise subspace and signal subspace, once there were a series of subspace projection methods to propose.Be about to filter weights to noise subspace (or signal subspace) projection, to obtain better resolution performance or robustness.But the restriction of this class methods performance acceptor spatial division levels of precision need strict division signals subspace and noise subspace, otherwise the method performance descends seriously.The present invention and subspace projection method are similar, but owing to the difference of having utilized between the power, the division of subspace is more careful, and the robustness of antithetical phrase spatial division error is stronger.

Describe the specific embodiment of the present invention in detail below in conjunction with accompanying drawing.

Fig. 1 adopts a kind of sky-wave OTH radar signal Processing of the present invention to concern process flow diagram, form unit 3, form by receiver unit 1, pulse compression unit 2, wave beam based on the noise jamming inhibition unit 4 of power distinction, relevant processing unit 5 and CFAR processing unit 6, the present invention is after wave beam forms unit 3, before relevant processing unit 5.

Fig. 2 is one embodiment of the present invention process flow diagrams, conciliates phase place pollution unit 4-5 by signal correlation matrix estimation unit 4-1, feature decomposition unit 4-2, eigenvector group division unit 4-3, signal taxon 4-4 and forms.

Sky-wave OTH radar receives L coherent pulse among the embodiment, and L is 512, and it also is 512 that DFT counts.

Radar receiver unit 1 will receive data and send, carry out pulse compression by 2 pairs of data of pulse compression unit, form unit 3 by wave beam again and carry out digital beam and form (conventional digital beam forms or adaptive beam forms), thereby obtain the recurrence interval data vector x of different distance door, different beams passage _Mn, it is sent into clutter and disturbs inhibition unit 4.

(1) signal correlation matrix estimation unit 4-1 all wave beams that will receive and the data x of range unit _MnCarry out the estimation of correlation matrix, obtain 512 * 512 matrix R:

$R=\frac{1}{\mathrm{MN}}\underset{m=1}{\overset{M}{\mathrm{\Σ}}}\underset{n=1}{\overset{N}{\mathrm{\Σ}}}{x}_{\mathrm{mn}}{x}_{\mathrm{mn}}^H$

M gets 600 among the embodiment, is all range gate numbers, and numbers of beams N gets 16.

(2) feature decomposition unit 4-2 carries out feature decomposition with correlation matrix R, obtains eigenwert vector matrix Λ and characteristic of correspondence vector matrix U:

R＝UΛU ^H

Wherein, Λ=diag{[λ ₁λ ₂λ _L] ^H, λ ₁〉=λ ₂〉=... 〉=λ _L, U=[u ₁u ₂U _L].

(3) eigenvector group division unit 4-3 is divided into strong clutter vector u according to the big young pathbreaker's feature matrix of eigenwert U ₁, clutter and interference vector group U _CI

The eigenwert size has reflected the watt level of respective signal to a certain extent, therefore can distinguish clutter, interference and target according to the eigenwert size.But how accurately to divide proper subspace according to the eigenwert size is one of difficult point of subspace projection class methods always.Among the embodiment, determine that by the priori threshold method big eigenwert number thresholding gets 60, utilized the power difference between clutter, interference and the target, avoided the group spatial division to have the problem that algorithm lost efficacy under the error condition.Certainly, do not have the big situation about entering between clutter and interference range of respective intended signal power thereby do not get rid of, sort signal disturbs and clutter although exist because power is bigger, still can detect.As for strong noise signal, mainly be to utilize it to carry out phase place to separate pollution, should adopt simple signal as far as possible, get final product so only need to keep eigenvalue of maximum characteristic of correspondence vector.

(4) signal taxon 4-4 utilizes the strong clutter vector u that obtains ₁With noise jamming set of vectors U _CIX is carried out the signal classification, wherein strong noise signal x _Cmn, clutter and undesired signal x _ImnWith echo signal x _TmnFor:

$x_{\mathrm{Cmn}}=u_1{u}_1^H{x}_{\mathrm{mn}}$

$x_{\mathrm{Imn}}=U_{\mathrm{CI}}{U}_{\mathrm{CI}}^H{x}_{\mathrm{mn}}$

$x_{\mathrm{Tmn}}=(I-U_{\mathrm{CI}}{U}_{\mathrm{CI}}^H)x_{\mathrm{mn}}$

X herein _CmnThe strong clutter data that comprise different beams and different distance unit, do on average to get final product than the strong clutter data of big range unit but in fact only need get wherein adjacent several wave beams and noise intensity:

x _MC＝mean(x _Cmn)

Clutter and undesired signal x _ImnNot only comprise interference, also comprise the high power signal that may exist, therefore also will be kept.

(5) the data x that utilizes signal taxon 4-4 to send here _MC, separate phase place and pollute unit 4-5 data x _ImnAnd x _TmnCarry out phase place and separate pollution:

Phase vectors in the attention formula

Element all are phase places behind the ambiguity solution.

At last, suppress and carried out the data that phase place separates after the pollution and deliver to the subsequent treatment unit with disturbing, be concerned with respectively by coherent accumulation unit 5 and CFAR processing unit 6 and handle and the CFAR processing, finish detection having finished clutter.

When the strong zone of actual clutter includes only data in the 200th to 500 range gate, for reducing calculated amount, the data of 200 to No. 500 range gate in the strong clutter district can be only got in the estimation of correlation matrix R, and promptly M gets 300.

Though described embodiments of the present invention in conjunction with the accompanying drawings, those of ordinary skills can make various distortion or modification within the scope of the appended claims.

Claims (5)

1. radar clutter and the multiple interference based on power distinction suppresses method simultaneously, comprises following technical step:

(1) receives that the punching press of data passages through which vital energy circulates is contracted and after wave beam forms, obtain recurrence interval data vector x _Mn, estimate its correlation matrix R:

$R=\frac{1}{\mathrm{MN}}\underset{m=1}{\overset{M}{\mathrm{\Σ}}}\underset{n=1}{\overset{N}{\mathrm{\Σ}}}{x}_{\mathrm{mn}}{x}_{\mathrm{mn}}^H$

Wherein, x _Mn=[x _Mn(1) x _Mn(2) ... x _Mn(l) ... x _Mn(L)] ^T, x _Mn(l) be the data of l recurrence interval of m range gate, a n wave beam passage, L is the recurrence interval number, and M is that range gate number, N are numbers of beams;

(2) R is carried out feature decomposition, obtain eigenvector group U by the big minispread of eigenwert;

(3) eigenvalue of maximum character pair vector is defined as strong clutter eigenvector u ₁, determine a big eigenwert number thresholding, from first big eigenwert until this thresholding, its character pair set of vectors is defined as clutter and disturbs character pair space U _CI

(4) utilize strong clutter eigenvector group, clutter and interference characteristic set of vectors to data x _MnCarry out filtering, data be divided into strong clutter, clutter and interference and three kinds of signals of target:

$x_{\mathrm{Cmn}}=u_1{u}_1^H{x}_{\mathrm{mn}}$

$x_{1\mathrm{mn}}=U_{\mathrm{CI}}{U}_{\mathrm{CI}}^H{x}_{\mathrm{mn}}$

$x_{\mathrm{Tmn}}=(I-U_{\mathrm{CI}}{U}_{\mathrm{CI}}^H)x_{\mathrm{mn}}$

Wherein, x _CmnBe strong noise signal, x _ImnBe clutter and undesired signal, x _TmnBe echo signal;

(5) utilize strong noise signal to carry out phase place and separate pollution, send subsequent treatment such as coherent accumulation, CFAR detection the data of separating after the pollution.

2. radar clutter and the multiple interference based on power distinction according to claim 1 suppresses method simultaneously, it is characterized in that, correlation matrix R can be by all wave beams and range unit data x _Mn(m=1,2 ..., Mn=1,2 ..., N) form, also can exist the data estimation of powerful clutter range unit to form by part wave beam and part.

3. radar clutter and the multiple interference based on power distinction according to claim 1 suppresses method simultaneously, it is characterized in that, the definite of big eigenwert number thresholding can also adopt the priori threshold method, sets different judgement thresholdings from small to large and handles respectively; When thresholding hour because interference noise is suppressed not thorough, false-alarm is more; Along with the raising of thresholding, noise jamming is inhibited, and detected target numbers will reduce gradually, when detected target numbers is stablized in the result, with corresponding threshold value as the priori threshold value in this irradiation area; The priori threshold value can obtain and store at off-line at ordinary times, directly utilizes this threshold value to distinguish the size of noise jamming feature space when handling in real time.

4. radar clutter and the multiple interference based on power distinction according to claim 3 suppresses method simultaneously, it is characterized in that, big eigenwert thresholding adopts the priori threshold method, more real-time simultaneously normalization characteristic spectrum and the expectation normalization characteristic spectrum that collects are at ordinary times revised big eigenwert thresholding when the two significant difference occurs.

5. radar clutter and the multiple interference based on power distinction according to claim 1 suppresses method simultaneously, it is characterized in that, utilize strong noise signal to carry out phase place and separate pollution and can also adopt the phase gradient method, proofread and correct clutter and the undesired signal x that is polluted with the phase information of strong noise signal _ImnWith echo signal x _Tmn:

Wherein, angle{} represents to get the ambiguity solution phase place of data in the bracket, and diag{} represents the diagonal matrix be made up of data vector in the bracket.

Images