CN102087354A - Passive radar grouping LS-CLEAN weak target detection method - Google Patents

Abstract

The invention provides a passive radar grouping LS-CLEAN weal target detection method. The method comprises the following steps of: averagely and continuously grouping all sampling points of radar reference signals and target echo signals; respectively projecting each group of target echo signals in a subspace being orthogonal with an interference subspace of each group; effectively suppressing direct wave interference and multipath interference; carrying out Doppler compensation on the echo signals; iteratively suppressing the shielding effect of a strong target sidelobe on weak target echo waves; calculating processed residual signal energy; when the residual signal energy is equivalent to a noise level, stopping iterating; and carrying out CFAR (Constant False Alarm Rate) processing on the signals at the moment to detect out weak targets. The method can be used for effectively suppressing direct wave interference, multipath interference and clutter interference and effectively eliminating the shielding effect of the strong target sidelobe on the weak target echo waves; by utilizing the method, the interference suppression residue can be reduced, and the calculated amount is small; and the method is suitable for real-time processing.

Description

Passive radar grouping LS-CLEAN Weak target detecting method

Technical field

What the present invention relates to is that a kind of GPS navigation satellite that utilizes is as the Weak target detecting method in the passive radar field in external radiation source.

Background technology

Passive radar is meant radar itself not electromagnetic signals and the radar of only using target emanation electromagnetic wave signal (external radiation source) to carry out target detection and tracking, and it has good " four resistance energy " and has low, disguised strong, the maneuverability advantages of higher of cost.The electromagnetic signal of target emanation may be the signal of target self emission, or the electromagnetic signal of third party's electromagnetic wave signal behind target reflection.Therefore, according to the target emanation type of signal source, passive radar can be divided into two classes: the one, utilize the passive radar of target self radiation source, and comprise the radiation source that target to be observed is self-contained, as electronic equipments such as radar, communication, answering machine, Active Jamming and navigation; The 2nd, utilize the third party to transmit through the passive radar of the signal of target reflection, this class emissive source comprises terrestrial broadcasting radio station, TV station, communication station, live telecast satellite and satellite navigation and location system etc.From radar system, its receiver is the strange land configuration with the transmitter that sends the external radiation source, so it also belongs to two (many) Ji Leida.

Have the advantage that a lot of traditional monostatic radars do not have based on gps signal as external radiation signal passive radar: (1) passive radar receiver is not owing to there is powerful device, and the influence that not leaked by transmitter power, thereby has higher sensitivity; (2) a plurality of operation of receiver can carry out passive location to interference source; (3) because sending and receiving split, and receiver is mourned in silence, also can be motor-driven, so system has the ability of anti-electronics investigation, the destruction of anti-interference and anti-antiradiation missile; (4) when receiver is preposition, can utilize irradiation source aerial, the space, can detect the following and deck-level target in far field of sight line of transmitter, anti-ultra-low altitude penetration ability is strong; (5) has anti-stealthy effect, because stealthy target only has minimum radar cross section (RCS) in ° scope of nose cone ± 30, and side direction and top scattering and diffraction do not reduce, and is also very strong, makes passive radar have good effect to the detection of stealthy target; (6) because self launching electromagnetic wave not, the passive radar system has disguise and emergentness, and the system survival ability is strong.

Core technology based on the passive radar of gps signal is passive relevant location technology, its basic thought be beyond radiation source emission the direct wave signal as a reference, the signal energy of check and analysis target reflection radiation source emission, estimate the parameters such as arrival direction, time of arrival and Doppler shift of target echo, thereby realize location and tracking target.Because gps satellite signal belongs to omnidirectional's continuous-wave radiation, the direct wave signal is very strong, exist multipath effect to make clutter stronger, and the echo of strong target also can disturb the detection of weak target echo greatly, need carry out therefore that clutter suppresses and signal Processing just can detect target to the non-co-operation signal that receives.

It is the guardian technique problem that the passive radar system is faced in signal Processing that undesired signal suppresses, the inhibition algorithm of taking at present mainly contains: (a) based on the interference nulling of the capable one-tenth of adaptive beam: ultimate principle is the amplitude and the phase place of regulating the bay weighting coefficient according to acceptance criteria automatically, make the cost function value minimum, make system reach optimum reception under this criterion, wherein to form be that two kinds of optimal beam that adaptive beam forms form devices for least mean-square error (MMSE) and linear restriction minimum variance (LCMV) criterion wave beam; (b) adopt adaptive filter algorithm to disturb inhibition; (c) direct wave based on subspace projection suppresses algorithm: this algorithm need not the required interference radiating way information of traditional adaptive disturbance null placing technique, also need not the reference channel in the sidelobe cancellation technology, but utilize the receiving end equivalent signal to construct the orthogonal intersection cast shadow matrix of direct wave subspace, carry out projection to received signal, disturb thereby suppress direct wave.

Summary of the invention

The object of the present invention is to provide and a kind ofly can suppress covering of direct wave interference, multipath interference, noise jamming, the strong target echo secondary lobe of elimination effectively, can detect the passive radar grouping LS-CLEAN Weak target detecting method of weak target echo.

The object of the present invention is achieved like this: with the average continuous grouping of all sampled points of radar reference signal, target echo signal, every group of echo signal be projected in respectively with this group disturb in the subspace of subspace quadrature, direct wave interference, multipath interference are effectively suppressed, echoed signal is carried out Doppler effect correction, further suppress the bridging effect of strong target secondary lobe iteratively, thereby accurately detect weak target, the LS-CLEAN method after the grouping can more efficiently inhibition be disturbed residue and strong target secondary lobe residue.

Receiving cable is divided into reference channel and target echo passage two parts in the system of the present invention, the direct signal of reference channel reception GPS navigation satellite as a reference, the target echo passage receives the signal of gps signal behind target reflection, also has direct wave interference, multipath interference and the strong target interference effect to weak target this moment.It is in the radar target passage that the present invention adopts the thought of the LS-CLEAN algorithm of grouping, and the signal errors quadratic sum minimum after make to disturb suppressing promptly makes the following formula minimum:

$\mathrm{\ξ}=\underset{i=i_1}{\overset{i_2}{\mathrm{\Σ}}}{|s_{\exp }\left(i\right)-s_{\mathrm{surv}\_c}\left(i\right)|}^2---\left(1\right)$

In the formula, ξ is for disturbing the signal errors quadratic sum after suppressing; || formula is represented the signal delivery; s _ExpIt is the radar target channel signal of expectation; s _{Surv_c}It is the output signal of utilizing after the LS-CLEAN algorithm that divides into groups carries out preliminary direct wave and multipath interference inhibition; To t observing time ₁t ₂Sample, the corresponding sampling points scope is i ₁i ₂, i is traversal sample range i ₁i ₂Sampled point.

In reference channel, (R is interested range points number for the simple crosscorrelation of target echo signal and reference signal on R range points before obtaining is exported, value in the light of actual conditions), reference signal is observed (R-1) individual sampled point more, reference signal is expanded to (N+R-1) individual sampled point (wherein N is the sampled point number of target echo signal after sampling), the reference battle array that the signal that received by reference channel this moment constitutes is:

s _ref＝[s _ref(-R+1)，·，s _ref(0)，·，s _ref(N-1)] ^T (2)

In the formula, s _RefExpression is with reference to battle array; s _Ref(i) be illustrated in the reference signal of i sampled point ,-R+1≤i≤N-1; [] ^TExpression is to transpose of a matrix.

Preceding K pending in reference channel time delay point handled (K is interested time delay point number, in the light of actual conditions value), and the time delay that structure has (K-1) individual time delay point with reference to battle array is:

S _{ref_d}＝[s _ref，Ds _ref，D ²s _ref，·，D ^k-1s _ref] (3)

In the formula, S _{Ref_d}Expression has the time delay of (K-1) individual time delay point with reference to battle array; D is the time delay battle array, and its form is as follows:

In the formula, d _IjBe positioned at the element of the capable j row of i among the expression time delay battle array D.

The time delay reference signal is constructed each different Doppler shifts, and time delay-Doppler of this moment with reference to battle array is:

S _{ref_df}＝[F _-pS _{ref_d}，·，F _-1S _{ref_d}，F ₀S _{ref_d}，F ₁S _{ref_d}，·，F _pS _{ref_d}] (5)

In the formula, S _{Ref_df}For having (K-1) individual time delay point, (2p+1) time delay-Doppler of individual Doppler shift point is with reference to battle array; F _pBe the Doppler shift battle array (p is interested Doppler shift point number, in the light of actual conditions value) of p Doppler shift point, as follows:

$F_p=\left[\begin{array}{cccc}1& 0& \·& 0\\ 0& e^{j2\mathrm{\πp}}& \·& 0\\ \·& \·& \·& \·\\ 0& 0& \·& e^{j2\mathrm{\πp}(N+R-1)}\end{array}\right]---\left(6\right)$

For will prolong-Doppler is with reference to the signal association of battle array and target echo passage output, utilize incidence matrix B to will prolong-Doppler handles with reference to battle array and obtains data battle array A, be shown below:

A＝BS _{ref_df} (7)

In the formula, B is an incidence matrix, is shown below:

In the formula, b _IjFor being positioned at the element of the capable j row of i among the incidence matrix B.

The column vector of data battle array A is constituted the interference subspace of (2p+1) K dimension, utilize projection operator P with the radar target signal projection to the subspace of disturbing the subspace quadrature in, projection operator P is expressed as:

P＝I-A(A ^HA) ^-1A ^H (9)

In the formula, A is a data matrix; A ^HHermitian matrix for A; () ^-1Be the inverse of a matrix matrix; I is and the unit matrix of A with dimension;

Received signal S with the radar target passage _SurvProjection in the subspace of disturbing the subspace quadrature in, played purpose to direct wave disturbs and the multipath interference suppresses.With radar target signal in the subspace of disturbing the subspace quadrature is exactly to make the signal of itself and wanted signal error sum of squares minimum, and the radar target signal after tentatively suppressing is:

s _{surv_c}＝Ps _surv＝I-A(A ^HA) ^-1A ^Hs _surv (10)

s _{Surv_c}Be to target echo signal s _SurvDirect wave disturb and multipath disturbs signal after suppressing, at this moment, the weak target echo is still because the bridging effect of strong target echo secondary lobe and not detectable, so will further remove the capture-effect of the strong target echo secondary lobe that has detected.

Pending reference signal and target echo signal are divided into continuous nb group, and every group sampling number is:

N _b＝N/n _b (11)

In the formula, N _bEvery group sampling number; N total sampling number when not dividing into groups; n _bFor the number of grouping, it is carried out value according to actual conditions.

After signal carried out packet transaction, through disturbing the target echo signal s after suppressing _{Surv_c}Can be expressed as:

$S_{\mathrm{surv}\_c}={[{{\stackrel{\‾}{S}}_{\mathrm{surv}\_c0}}^T,{{\stackrel{\‾}{S}}_{\mathrm{surv}\_c1}}^T,\·,{{\stackrel{\‾}{S}}_{\mathrm{surv}\_c(n_b-1)}}^T]}^T---\left(12\right)$

In the formula, [] ^TExpression is carried out transposition to matrix;

Expression is disturbed and is suppressed back i group (0≤i≤n _b-1) radar target signal, its expression formula is as follows:

${\stackrel{\‾}{S}}_{\mathrm{surv}\_\mathrm{ci}}={\stackrel{\‾}{s}}_{\mathrm{survi}}-{\stackrel{\‾}{A}}_i(I-P){\stackrel{\‾}{s}}_{\mathrm{survi}}---\left(13\right)$

In the formula, After the signal that expression receives the radar target passage divided into groups, i organized (0≤i≤n _b-1) target echo signal; After expression was divided into groups to data battle array A, i organized (0≤i≤n _b-1) data battle array.

After signal carried out packet transaction, reference signal

Can be expressed as:

${\stackrel{\‾}{s}}_{\mathrm{refi}}={[s_{\mathrm{ref}}({\mathrm{iN}}_b-R+1),s_{\mathrm{ref}}({\mathrm{iN}}_b-R),\·,s_{\mathrm{ref}}((i+1)N_b-1)]}^T---\left(14\right)$

In the formula, Reference signal after the expression grouping; I represents grouping serial number, i=0, and 1,, n _b-1.

After signal carried out packet transaction, the radar target signal

Can be expressed as:

${\stackrel{\‾}{s}}_{\mathrm{survi}}={[s_{\mathrm{surv}}\left({\mathrm{iN}}_b\right),s_{\mathrm{surv}}({\mathrm{iN}}_b+1),\·,s_{\mathrm{surv}}((i+1)N_b-1)]}^T---\left(15\right)$

In the formula,

Radar target signal after the expression grouping; I represents grouping serial number, i=0, and 1,, n _b-1.

At first, to the s after the grouping _{Surv_c}Carry out Doppler shift compensation (compensation method inferior do not do concrete research), the strong target peak secondary lobe of the matched filtering output terminal after the compensation is carried out iteration suppress.

Signal after the signal in the radar target passage being carried out direct wave, multipath, noise jamming suppresses and carrying out Doppler effect correction is output as C through matched filter _InterThe capture-effect of strong target echo secondary lobe finally detects the weak target echoed signal according to by suppressing successively to weak order by force.When suppressing strong target echo capture-effect, the initialization process matrix S makes processing array be at initial time first:

S ₀＝C _inter (16)

In the formula, S is a processing array, and following footnote is represented iterations, S ₀Initial value for processing array; C _InterBe matched filter output.

Carrying out the j time iteration when suppressing (iterations j should more than the target number), processing array S upgraded according to following principle:

S _j+1(i＝delay _j-N，·，delay _j+N)＝S _j(i＝delay _j-N，·，delay _j+N)-m _jC _A (17)

In the formula, C _ABe reference signal s _RefAutocorrelation matrix; m _j=max (| S _j|) be S _jMaximal value; Delay _j=arg{max (| S _j|) be the time delay of maximal value correspondence.

Through iterative processing, detected target echo signal is:

s _wtj(i)＝s _wtj-1(i)+m _jδ(i-delay _i) (18)

In the formula, s _Wtj-1Detected target echo when (i) being preceding (j-1) inferior iteration; I is the time delay of this moment; δ is an impulse response function.

The end condition of iteration is as follows: the energy to residual signal calculates, if it is near the noise level of expectation, then iteration finishes, the s of this moment _WtBe the weak target that has detected; Otherwise, if far above noise level, illustrating, the residual signal energy still have target echo to exist, the weak target that then carries out next time detects processing.

Of the present invention in based on the passive radar detection system of GPS navigation satellite as the external radiation source, the method of utilizing the LS-CLEAN algorithm that divides into groups to carry out the weak target detection has following good effect and advantage: employing the method can suppress the direct wave interference effectively, multipath disturbs and noise jamming, can also eliminate the capture-effect of strong target echo secondary lobe effectively to the weak target echo, utilize the method to make and disturb and suppress the residue reduction, calculated amount is easy simultaneously, is fit to handle in real time.

Description of drawings

Fig. 1 is based on the passive radar system schematic of GPS navigation satellite as the external radiation source;

Fig. 2 is based on the passive radar packet signal processing procedure of GPS navigation satellite as the external radiation source;

Fig. 3 utilizes grouping LS-CLEAN method to carry out the enforcement block diagram of weak target testing process.

Embodiment

In conjunction with the accompanying drawings the present invention is further elaborated.As shown in Figure 1, belong to many bases passive radar detection system based on the GPS navigation satellite as the passive radar detection system in external radiation source, receive the radiofrequency signal of 4 GPS navigation satellites transmits at the passive radar receiver end, receiving system is divided into reference channel and radar target passage, is used for receiving the direct wave signal respectively and through the echoed signal of target reflection.

As shown in Figure 2, adopt the GPS receiver of standard in reference channel, the signal that receives carries out purification processes as the reference signal to it; In the radar target passage, that the signal that receives comprises is strong, echoed signal, direct wave interference, multipath interference, noise jamming and the noise etc. of weak target.At first it is amplified and filtering, being down-converted to intermediate frequency then handles, remove the navigation information that carries in the gps signal, utilize the LS-CLEAN method of grouping to carry out direct wave and clutter inhibition, signal and reference signal after suppressing are carried out matched filtering, at first carry out Doppler effect correction at the output terminal of matched filter, the bridging effect to weak target suppresses to strong target secondary lobe again, last coherent accumulation, CFAR are handled, and reach the purpose that detects weak target.

In conjunction with Fig. 3, it is as follows that the present invention utilizes grouping LS-CLEAN to carry out the process that weak target detects:

(1) at first utilize grouping LS-CLEAN method to carry out direct wave and clutter inhibition;

(2) target echo signal after reference signal after the grouping and the inhibition is carried out matched filtering;

(3) calculate peak value-secondary lobe than (PSLR), peak value-noise ratio (PNFR), range resolution, DOPPLER RESOLUTION;

(4) compare PSLR and PNFR, if PSLR＜PNFR carry out step 5; Otherwise carry out step 9;

(5) permanent threshold processing;

(6) iteration is carried out strong target echo secondary lobe capture-effect inhibition;

(7) carry out matched filter processing;

(8) recomputate PNFR, carry out step 4 once more, itself and PSLR size are compared;

(9) CFAR is handled;

(10) draw testing result.

In the weak target processing procedure, at the matched filter output terminal, eliminate of the bridging effect of the secondary lobe of strong target to the weak target echo, effectively reduce the dump energy of disturbing after suppressing.

Claims (2)

1. passive radar grouping LS-CLEAN Weak target detecting method, it is characterized in that: with the radar reference signal, the average continuous grouping of all sampled points of target echo signal, every group of target echo signal be projected in respectively with this group disturb in the subspace of subspace quadrature, direct wave is disturbed, multipath disturbs and effectively suppresses, echoed signal is carried out Doppler effect correction, suppress of the bridging effect of strong target secondary lobe iteratively to the weak target echo, residual signal energy after the computing, when the residual signal energy is suitable with noise level, stop iteration, signal to this moment carries out the CFAR processing, detects weak target.

2. passive radar grouping LS-CLEAN Weak target detecting method according to claim 1 is characterized in that specifically comprising the steps:

(1) at first utilize grouping LS-CLEAN method to carry out direct wave and clutter inhibition;

(2) target echo signal after reference signal after the grouping and the inhibition is carried out matched filtering;

(3) calculating peak value-secondary lobe ratio is that PSLR, peak value-noise ratio are PNFR, range resolution, DOPPLER RESOLUTION;

(4) compare PSLR and PNFR, if PSLR＜PNFR carry out step 5; Otherwise carry out step 9;

(5) permanent threshold processing;

(6) iteration is carried out strong target echo secondary lobe capture-effect inhibition;

(7) carry out matched filter processing;

(8) recomputate PNFR, carry out step 4 once more, itself and PSLR size are compared;

(9) CFAR is handled;

(10) draw testing result.

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