CN103885052B - A kind of polar echo separation method of wide cut complete polarization satellite-borne SAR - Google Patents

Abstract

A polar echo separation method for wide cut complete polarization satellite-borne SAR, wide cut complete polarization satellite-borne SAR refers to launches successively H and V polarization pulse in a pulse recurrence interval, then utilizes dual polarization passage to receive echo, thereby obtains the new system of four kinds of polarization components. This novel complete polarization SAR can not increase system repetition, therefore can obtain wider mapping band. But, for obtaining this performance boost, just must first the echo free of different polarization pulses be opened. This method retrains in conventional linear on the basis of minimum variance (LCMV) algorithm and improves: traditional algorithm is split, and introduced FIR filtering between two steps that split, then second step is done to corresponding improvement adjustment. Realize polar echo according to this method and separate, can make the separation isolation of different polar echos meet application demand on the one hand, also without excessively increasing operand on star, reduced Project Realization difficulty on the other hand.

Description

A kind of polar echo separation method of wide cut complete polarization satellite-borne SAR

Technical field

The present invention is directed to critical problem-aliasing echo of New System wide cut complete polarization Spaceborne SAR SystemSeparating treatment, a kind of novel polarization echo free method is provided, be mainly concerned with microwave remote sensing andSignal is processed two large technical fields.

Background technology

Receive echo, complete polarization satellite-borne SAR energy by launching different polarization pulses and dual polarization passageEnough scattered information that obtains each resolution cell under difference polarization combination, this contributes to further to understand orderTarget backscattering characteristic. Therefore,, than single polarization SAR, complete polarization SAR can provide moreAbundant target information, contributes to determine target scattering mechanism, promotes the detection discriminator energy to targetPower and suppressing the noise jamming receiving. Due to the introducing of complete polarization technology, SARApplication greatly widened. By full polarimetric SAR, we can extract moreInformation, these information are in agricultural monitoring, hydro_geography, urban planning, Disaster Assessment and military surveillanceThere is the effect that cannot estimate in field.

Present stage, a series of complete polarization Spaceborne SAR System were in orbit (as moral aerospaceTerraSAR-X, the RADARSAT-2 of Canadian space agency etc.) be all to adopt alternate emission H/VPolarization pulse is realized complete polarization earth observation imaging with the mode that dual polarization passage reception echo combines, the transmission interval of two kinds of polarization pulses is pulse recurrence interval (PRI, PulserepetitionInterval), as shown in accompanying drawing 1 (a). This polarization mode need promote one times with the side of avoiding by system PRFThe deterioration that position is fuzzy, thus cause imaging fabric width to reduce half, reducing and heavily visited observing frequency, this is alsoThe maximum drawback of complete polarization satellite-borne SAR at present.

For overcoming the above problems, moral aerospace DLR has proposed a kind of novel complete polarization in 2008 spaceborneSAR system, this system can be launched continuously two kinds of polarization pulse (accompanying drawings 1 (b) during pulsatile once transmittingShown in shown in accompanying drawing 2), receive by dual polarization passage again at receiving terminal, just can obtain in theoryWhole four kinds of polarization components, needn't improve system PRF again and realize complete polarization observation. In this systemAfter proposition, both at home and abroad its feasibility in theory is unanimously approved, but thought this system Project Realization simultaneouslyBiggest obstacle is different polarization pulse echos aliasings in time. If they effectively can not be separated,Cannot extract each polarization components.

For this problem of echo free, DLR is delivering without open source literature or patent in recent years, because ofThis cannot know this mechanism in this work progress situation on the one hand by open channel. Aspect at home,The Qi Weikong of Chinese Academy of Sciences electron institute has delivered one section and has been called " newly a kind of on publication " Chinese science E periodical "The research of multipolarization satellite-borne SAR working method " article study and address this problem, described in literary compositionMethod need to complete Range compress processing on star, then carries out to range gate one by one zero again and falls into inhibition placeReason. Owing to will complete Range compress on star, therefore greatly increase the operand on star, on starResource requirement is very high, is difficult to through engineering approaches and realizes. In a word, by the end of at present, also not on open source literatureSee that the through engineering approaches having for the problems referred to above can publish by implementation.

Summary of the invention

Technology of the present invention is dealt with problems and is: overcome the deficiencies in the prior art, for New System complete polarization starThe echo Aliasing Problem that carries SAR, the present invention proposes a kind of novel pitching and forms method to digital beam.This method is by the linear restriction minimum variance (Linear that tradition sensing at zero point processing is adoptedConstraintMinimumVariance, LCMV) algorithm improves, and upwards forms two in pitchingDigital reception beam is realized airspace filter (accompanying drawing 3), has just completed two kinds of polarization at echo reception periodThe separation of echo.

Technical solution of the present invention is:

A polar echo separation method for wide cut complete polarization satellite-borne SAR, described polar echo is oneIn pulse recurrence interval successively transmitting H polarization pulse and the corresponding echo of V polarization pulse, and this twoPlant echo be back to receiver from different positions, visual angle simultaneously in echo receiver window, thereby in time domainAliasing; The step of described separation method is as follows:

(1) to Planar Phased Array Antenna pitching, upwards received echo is successively in each receive pathCarry out low noise amplification, down coversion and ADC sampling processing, by high frequency simulation corresponding original echoSignal becomes low-frequency digital signal;

(2) utilize the real-time ripple of described H polarization pulse and V polarization pulse to reach vector v₁With v₂Right respectivelyThe low-frequency digital signal that step (1) obtains is weighted processing, and wherein pitching receives logical to kThe low-frequency digital signal in road is respectively by v₁With v₂K element w_1kWith w_2kWeighting, k is positive integer, andk∈[1,N_e],N_eFor the number of receive path;

(3) by pitching to two-way in each receive path through different weights v₁With v₂The signal of weighting carries outCorresponding FIR filtering processing;

(4) the process weight vectors v of each receive path output₁And the signal of FIR filter processVector adds up and synthesizes output, generates a road signal; The process weight vectors of each receive path outputv₂And the synthetic output that adds up of the signal phasor of FIR filter process, generate another road signal;

(5) by first group of weight vectorsThe two paths of signals that step (4) is obtained addsPower synthetic output, obtains the H polarization pulse of first transmitting during a complete impulse ejectionEcho-signal;

(6) by second group of weight vectorsThe two paths of signals that step (4) is obtained addsThe synthetic output of power, obtains the returning of V polarization pulse of second transmitting during a complete impulse ejectionRipple signal.

In described step (2) two the described H polarization pulse of transmitting and the ripples of V polarization pulse successivelyReach vector v₁With v₂While being, become, its expression formula is respectivelyWithK the element that ripple reaches in vector can be expressed as $W_{\mathrm{ik}}=\exp \{j\frac{2\mathrm{\π}}{\mathrm{\λ}}(k-1)d\·\sin [{\mathrm{\θ}}_i\left(\mathrm{\τ}\right)\left]\right\}(i=\mathrm{1,2}),$ I=1 interval scale H polarization pulse, i=2 interval scaleV polarization pulse;

Wherein λ is that wavelength, d are that pitching is to receive path interval, θ_i(τ) be H polarization pulse (i=1) orThe echo of V polarization pulse (i=2) is at Bo Dajiao corresponding to τ moment, and its account form is entered as followsOK:

(a) calculate corresponding instantaneous at the echo of τ moment H polarization pulse by formula R (τ)=c τ/2Oblique distance R; Wherein c is the light velocity; The oblique distance of V polarization pulse echo can be expressed as R'(τ)=c (τ-T)/2, itsMiddle T is two transmission intervals between polarization pulse;

(b) according to the instantaneous oblique distance R (τ) calculating in step (a), according to formulaSolve the instantaneous substar visual angle of H polarization pulse echoα (τ), wherein R_eFor earth radius, H is satellite orbital altitude;

(c) according to antenna pitching to normal direction substar visual angle α_cAnd the wink calculating in step (b)Shi Huibo substar visual angle α (τ), utilizes formula θ (τ)=α (τ)-α_cTry to achieve the corresponding ripple of echo and reach angle.

FIR wave filter in described step (3) is one 8 rank Time-Delay Filters, and pitching connects to kReceiving the corresponding delay volume of passage isWherein K_rFor exomonental linear tuneFrequency,For passing through scene center moment τ in pulse_cShi Bo reaches angle θ (τ) and adjusts the distance to fast time τSingle order local derviation.

Weight vectors in described step (5) and (6)Be respectively matrixN_e[(V')^HV']^-1The first row and the second row, wherein, (V')^HV' is obtained by following formula:

${\left(v^{\′}\right)}^H{v}^{\′}=\left[\begin{array}{cc}\underset{k=1}{\overset{N_e}{\mathrm{\Σ}}}{f^{\′}}_{11k}\left(\mathrm{\τ}\right)& \underset{k=1}{\overset{N_e}{\mathrm{\Σ}}}{f^{\′}}_{12k}\left(\mathrm{\τ}\right)\\ \underset{k=1}{\overset{N_e}{\mathrm{\Σ}}}{f^{\′}}_{21k}\left(\mathrm{\τ}\right)& \underset{k=1}{\overset{N_e}{\mathrm{\Σ}}}{f^{\′}}_{22}k\left(\mathrm{\τ}\right)\end{array}\right],$ Element f' shown in matrix_ijk(τ) can be expressed as

${f^{\′}}_{\mathrm{ilk}}\left(\mathrm{\τ}\right)=\exp \{j\frac{2\mathrm{\π}}{\mathrm{\λ}}(k-1)d\·\{\sin \left[{\mathrm{\θ}}_j(\mathrm{\τ}+D_k)\right]-\sin \left[{\mathrm{\θ}}_i(\mathrm{\τ}+D_k)\right]\left\}\right\},$ i,j=1,2,k∈[1,N_e]，θ₂Represent the Bo Dajiao of V polarization pulse, θ₁Represent the Bo Dajiao of H polarization pulse.

The present invention's beneficial effect is compared with prior art:

(1) compared with the present invention processes with tradition sensing at zero point, considered that pulse ductility is to separation propertyThe impact of energy. Because subpulse all has certain pulsewidth, all a certain particular moment its on ground allCan cover certain region, can only realize the center of institute overlay area and point to method traditional zero pointLarge gain receives (signal subspace pulse)/the darkest zero and falls into inhibition (interference subpulse), and cannot be real to other regionThe now gain identical with center receives, and therefore cause isolation poor, and the present invention can be by isolationDegree promotes about 10dB, makes the isolation of two kinds of polar echos in whole receiver window be greater than 25dB,Meet most polarization SAR application demands.

(2) the synthetic processing of a step weighting of tradition sensing at zero point is split into two steps by the present invention, and twoStep weighting has been introduced 8 rank FIR filtering (shown in accompanying drawing 4) between processing. The compression of this and advanced row distance,Range gate is done and is pointed to the echo free flow process of processing zero point and compare one by one again, has greatly reduced on star to beSystem structure and process accordingly operand, is conducive to through engineering approaches and realizes.

Brief description of the drawings

Fig. 1 is the scheme comparison of traditional system and New System complete polarization satellite-borne SAR, and wherein Fig. 1 (a) isThe complete polarization scheme of traditional system, Fig. 1 (b) is New System complete polarization scheme;

Fig. 2 is the impulse ejection sequential chart of New System wide cut complete polarization Spaceborne SAR System;

Fig. 3 is pitching separates polar echo from diverse location place to two digital beams of DBF formation;

Fig. 4 is pitching to corresponding 8 rank FIR filter process block diagrams in k sub-aperture;

Fig. 5 points to the system block diagram that is divided into two steps the traditional zero point based on LCMV algorithm;

Fig. 6 is the schematic diagram of polar echo separation method of the present invention.

Detailed description of the invention

Below in conjunction with accompanying drawing, innovative point of the present invention and detailed description of the invention are elaborated.

Due to two kinds of polaron pulses (two kinds of polarization of H and V of New System wide cut complete polarization satellite-borne SARPulse) launch successively, therefore in any time of echo receiver window, two kinds of polarization pulses of H and VEcho can be back to receiver from different visual angles respectively, and the earth's surface information that contains zones of different is (attachedShown in Fig. 3). According to this difference, we can utilize digital beam to form (DBF) technology receiving terminal shapeThe received beam of two real time scans of one-tenth receives respectively the echo of H and V polarization pulse, and each wave beamThere is the feature of following two aspects:

1, maximum gain receives the echo of corresponding subpulse

2, the darkest zero fall into the echo that suppresses to disturb subpulse

In various beamforming algorithms, linear restriction minimum variance (LCMV) method can realize above two

Aspect performance. This algorithm is determined by following equation group:

$W_i^H{v}_i=N_e---\left(1.1\right)$

$W_i^H{v}_j=0(i\≠j)---\left(1.2\right)$

Wherein i, (as subscript i, j=1 represents that relevant parameter is the relevant parameter of H polarization pulse to j ∈ [1,2], i, j=2 tableShow that parameter is the relevant parameter of V polarization pulse), symbol ()^HRepresent conjugate transpose, w_iRepresent to form theThe weight vectors of i beamlet, N_eRepresent pitching to the sub-aperture number of reception (receive path quantity),v_iAnd v_jRepresent respectively i and j the corresponding steering vector of subpulse (steeringvecotr),They can be expressed as respectively

$v_i={[1,\exp \{j\frac{2\mathrm{\π}}{\mathrm{\λ}}d\sin \left({\mathrm{\θ}}_i\right)\},...,\exp \{j\frac{2\mathrm{\π}}{\mathrm{\λ}}(N_e-1)d\sin \left({\mathrm{\θ}}_i\right)\left\}\right]}^T---\left(2.1\right)$

With

$v_i={[1,\exp \{j\frac{2\mathrm{\π}}{\mathrm{\λ}}d\sin \left({\mathrm{\θ}}_i\right)\},...,\exp \{j\frac{2\mathrm{\π}}{\mathrm{\λ}}(N_e-1)d\sin \left({\mathrm{\θ}}_i\right)\left\}\right]}^T---(2.2)$

Wherein ()^TFor transposition symbol, d be pitching to interval, sub-aperture, λ is wavelength, θ_iWith θ_jRepresent respectively iThe individual pitching corresponding with the individual sub-pulse echo of j is to normal direction deviation angle (off-boresightangle),Ripple reaches angle. Because subpulse is advanced on ground, therefore steering vector v_iAnd v_jWhile being, become, thisAlso determined corresponding weight vectors w_iWith w_jWhile being, become.

Based on formula (2.1) and formula (2.2), definition receiving array multiple matrix V is

V=[v₁,v₂](3)

Thus, wave beam is formed to weight vectors w_iRestrictive condition (1.1) and (1.2) can be expressed as matrix sideJourney

$W_i^{H}V=N_e\·e_i^T---\left(4\right)$

Wherein e_iBe the i row of one 2 × 2 unit matrixs. By separating above equation group, we can draw and form theI receives the weight vectors w of beamlet_iFor

$W_i^H=N_e\·e_i^T{\left(V^H{S}_{\mathrm{tn}}^{-1}V\right)}^{-1}{V}^H{S}_{\mathrm{tn}}^{-1}---\left(5\right)$

Wherein S_tnFor the covariance matrix (spectralmatrix) of receiver noise. This noise can be modeled as whiteNoise and power areS_tnCan be write as

$S_{\mathrm{tn}}={\mathrm{\σ}}_{\mathrm{tn}}^2\·I_{N_e\×N_e}---\left(6\right)$

WhereinBe a N_eThe unit matrix of dimension. Formula (6) is brought into formula (5),Can be reduced to

$w_i^H=N_e\·e_i^T{\left(V^{H}V\right)}^{-1}{V}^H---\left(7\right)$

But because pulse has certain pulsewidth, therefore it has certain ductility on the ground, utilizeI the reception beamlet that the represented weight vectors of formula (7) forms can only form maximum in a certain positionGain/the darkest zero falls into, and all the other positions cannot obtain the receiving gain identical with center, and this can be rearPhase is caused the problem that separating degree is inadequate.

For this problem, we change the novelty of tradition sensing at zero point processing being done to following three aspects:Enter, to obtain more excellent separating effect:

(1) synthetic traditional LC MV weighting represented formula (7) processing is split into two steps. The first step byTwo row vectors that matrix V H comprises are synthetic defeated to the primary signal weighting of array received to pitching respectivelyGo out; Second step is to utilize row vectorThe two paths of signals that the first step is exported is weightedSynthetic. Accompanying drawing 5 has provided the schematic diagram that traditional LC MV weighting processing is split into two steps.

(2) by analyzing SAR echo through first step characteristics of signals after treatment, the first step completes itAfter in each passage, introduced FIR filtering processing in pitching, the filter system in k sub-aperture ringsAnswer function

$H_{\mathrm{FIR}\_k}\left(f\right)=\exp \left\{j2\mathrm{\π}\frac{(k-1)f_0}{K_r}f\right\}---\left(8\right)$

Wherein K_rFor exomonental FM signal,(d be pitching to interval, sub-aperture, λ isWavelength,For saving partially micro-for distance to one of fast time τ in echo window center moment echo visual anglePoint). H_{FIR_k}(f) phase place is the linear function of frequency f, in the corresponding time domain of this ssystem transfer functionDelay process, this can realize (shown in accompanying drawing 3) by the sinc interpolation kernel of 8 on star.

(3) after FIR filtering is processed, again according to characteristics of signals, second after LCMV is splitThe vector of step weighting processingDo corresponding correction, becomeEnsure relevant the synthesizing between signal, made finally to obtain optimum echo free effect.

Note:

$v^{H}v=\left[\begin{array}{cc}\underset{k=1}{\overset{N_e}{\mathrm{\Σ}}}{f}_{11k}\left(\mathrm{\τ}\right)& \underset{k=1}{\overset{N_e}{\mathrm{\Σ}}}{f}_{12k}\left(\mathrm{\τ}\right)\\ \underset{k=1}{\overset{N_e}{\mathrm{\Σ}}}{f}_{21k}\left(\mathrm{\τ}\right)& \underset{k=1}{\overset{N_e}{\mathrm{\Σ}}}{f}_{22k}\left(\mathrm{\τ}\right)\end{array}\right]---\left(9\right)$

Wherein ${f^{\′}}_{\mathrm{ilk}}\left(\mathrm{\τ}\right)=\exp \{j\frac{2\mathrm{\π}}{\mathrm{\λ}}(k-1)d\·\{\sin \left[{\mathrm{\θ}}_j\left(\mathrm{\τ}\right)\right]-\sin \left[{\mathrm{\θ}}_i(\mathrm{\τ}+D_k)\right]\left\}\right\},$ And (V')^HV' is

${\left(v^{\′}\right)}^H{v}^{\′}=\left[\begin{array}{cc}\underset{k=1}{\overset{N_e}{\mathrm{\Σ}}}{f^{\′}}_{11k}\left(\mathrm{\τ}\right)& \underset{k=1}{\overset{N_e}{\mathrm{\Σ}}}{f^{\′}}_{12k}\left(\mathrm{\τ}\right)\\ \underset{k=1}{\overset{N_e}{\mathrm{\Σ}}}{f^{\′}}_{21k}\left(\mathrm{\τ}\right)& \underset{k=1}{\overset{N_e}{\mathrm{\Σ}}}{f^{\′}}_{22}k\left(\mathrm{\τ}\right)\end{array}\right]---\left(10\right)$

Wherein ${f^{\′}}_{\mathrm{ilk}}\left(\mathrm{\τ}\right)=\exp \{j\frac{2\mathrm{\π}}{\mathrm{\λ}}(k-1)d\·\{\sin \left[{\mathrm{\θ}}_j(\mathrm{\τ}+D_k)\right]-\sin \left[{\mathrm{\θ}}_i(\mathrm{\τ}+D_k)\right]\left\}\right\},$ In formula's $D_k=\frac{(k-1)}{K_r}{f}_0.$

In specific implementation process, first need complete polarization satellite-borne SAR upwards to there is multiple connecing in pitchingReceive sub-aperture (shown in accompanying drawing 3). The echo that the sub-aperture of each reception receives is through LNA, down coversionAnd after ADC sampling, implement according to following flow process:

(1) utilize the first step that point in processing the traditional zero point being split out to enter digital echo signalRow weighting processing;

(2) by each pitching to receive in sub-aperture corresponding FIR wave filter to step (1) weighting afterSignal do corresponding time delay processing;

(3) last, utilize the signal that in the sensing processing at zero point after improving, second step obtains step (2) to doCorresponding weighting is synthetic to be processed, and can obtain H and the V polar echo separated.

This method of the present invention design can meet the separation requirement of practical application to different polar echos,And not high to operand demand on star, can on star, just realize in real time and separating. Corresponding system processing blockAs shown in Figure 6, step is as follows for figure:

(1) to Planar Phased Array Antenna pitching, upwards received echo is successively in each receive pathCarry out low noise amplification, down coversion and ADC sampling processing, by high frequency simulation corresponding original echoSignal becomes low-frequency digital signal;

(2) utilize the real-time ripple of described H polarization pulse and V polarization pulse to reach vector v₁With v₂Right respectivelyThe low-frequency digital signal that step (1) obtains is weighted processing, and wherein pitching receives logical to kThe low-frequency digital signal in road is respectively by v₁With v₂K element w_1kWith w_2kWeighting, k is positive integer, andk∈[1,N_e],N_eFor the number of receive path;

Described two described H polarization pulses of launching successively and the ripple of V polarization pulse reach vector v₁With v₂BeTime become, its expression formula is respectivelyRipple reachesK element in vector can be expressed as $W_{\mathrm{ik}}=\exp \{j\frac{2\mathrm{\π}}{\mathrm{\λ}}(k-1)d\·\sin [{\mathrm{\θ}}_i\left(\mathrm{\τ}\right)\left]\right\}(i=\mathrm{1,2}),$ When i=1Represent H polarization pulse, i=2 interval scale V polarization pulse;

Wherein λ is that wavelength, d are that pitching is to receive path interval, θ_i(τ) be i sub-pulse echo (i=1For the pulse of H polaron, i=2 is the pulse of V polaron) in Bo Dajiao corresponding to τ moment, its account formCarry out as follows:

(a) calculate corresponding instantaneous at the echo of τ moment H polarization pulse by formula R (τ)=c τ/2Oblique distance R; Wherein c is the light velocity; The oblique distance of V polarization pulse echo can be expressed as R'(τ)=c (τ-T)/2, itsMiddle T is two transmission intervals between polarization pulse;

(b) according to the instantaneous oblique distance R (τ) calculating in step (a), according to formula

Solve the instantaneous substar visual angle of H polarization pulse echoα (τ), wherein R_eFor earth radius, H is satellite orbital altitude;

(c) according to antenna pitching to normal direction substar visual angle α_cAnd the wink calculating in step (b)Shi Huibo substar visual angle α (τ), utilizes formula θ (τ)=α (τ)-α_cTry to achieve the corresponding ripple of echo and reach angle.

(3) by pitching to two-way in each receive path through different weights v₁With v₂The signal of weighting carries outCorresponding FIR filtering processing;

Described FIR wave filter is one 8 rank Time-Delay Filters, when pitching is corresponding to k receive pathThe amount of prolonging beWherein K_rFor exomonental linear frequency modulation rate,ForAt pulse process scene center moment τ_cShi Bo reaches angle θ (τ) and adjusts the distance to the single order local derviation of fast time τ.

(4) the process weight vectors v of each receive path output₁And the signal of FIR filter processVector adds up and synthesizes output, generates a road signal; The process weight vectors of each receive path outputv₂And the synthetic output that adds up of the signal phasor of FIR filter process, generate another road signal;

(5) by first group of weight vectorsThe two paths of signals that step (4) is obtained addsPower synthetic output, obtains the H polarization pulse of first transmitting during a complete impulse ejectionEcho-signal;

(6) by second group of weight vectorsThe two paths of signals that step (4) is obtained addsThe synthetic output of power, obtains the returning of V polarization pulse of second transmitting during a complete impulse ejectionRipple signal.

Weight vectors in step (5) and (6)Be respectively matrix N_e[(V')^HV']^-1The first row and the second row, wherein, (V')^HV' is obtained by following formula:

${\left(v^{\′}\right)}^H{v}^{\′}=\left[\begin{array}{cc}\underset{k=1}{\overset{N_e}{\mathrm{\Σ}}}{f^{\′}}_{11k}\left(\mathrm{\τ}\right)& \underset{k=1}{\overset{N_e}{\mathrm{\Σ}}}{f^{\′}}_{12k}\left(\mathrm{\τ}\right)\\ \underset{k=1}{\overset{N_e}{\mathrm{\Σ}}}{f^{\′}}_{21k}\left(\mathrm{\τ}\right)& \underset{k=1}{\overset{N_e}{\mathrm{\Σ}}}{f^{\′}}_{22}k\left(\mathrm{\τ}\right)\end{array}\right],$ Element f' shown in matrix_ijk(τ) can be expressed as

${f^{\′}}_{\mathrm{ilk}}\left(\mathrm{\τ}\right)=\exp \{j\frac{2\mathrm{\π}}{\mathrm{\λ}}(k-1)d\·\{\sin \left[{\mathrm{\θ}}_j(\mathrm{\τ}+D_k)\right]-\sin \left[{\mathrm{\θ}}_i(\mathrm{\τ}+D_k)\right]\left\}\right\},$ i,j=1,2,k∈[1,N_e]，θ₂Represent the Bo Dajiao of V polarization pulse, θ₁Represent the Bo Dajiao of H polarization pulse.

The content not being described in detail in description of the present invention belongs to the known of professional and technical personnel in the fieldTechnology.

Claims (5)

1. a polar echo separation method for wide cut complete polarization satellite-borne SAR, described polar echo is oneH polarization pulse and the corresponding echo of V polarization pulse in individual pulse recurrence interval, launched successively, these are two years oldPlant echo be back to receiver from different positions, visual angle simultaneously in echo receiver window, thereby in time domainAliasing; It is characterized in that: the step of described separation method is as follows:

(1) to Planar Phased Array Antenna pitching, upwards received echo is successively in each receive pathCarry out low noise amplification, down coversion and ADC sampling processing, by high frequency simulation corresponding original echoSignal becomes low-frequency digital signal;

(2) utilize the real-time ripple of described H polarization pulse and V polarization pulse to reach vector v₁With v₂Right respectivelyThe low-frequency digital signal that step (1) obtains is weighted processing, and wherein pitching receives logical to kThe low-frequency digital signal in road is respectively by v₁With v₂K element w_1kWith w_2kWeighting, k is positive integer, andk∈[1,N_e],N_eFor the number of receive path;

(3) by pitching to two-way in each receive path through different weights v₁With v₂The signal of weighting carries outCorresponding FIR filtering processing;

(4) the process weight vectors v of each receive path output₁And the signal of FIR filter processVector adds up and synthesizes output, generates a road signal; The process weight vectors of each receive path outputv₂And the synthetic output that adds up of the signal phasor of FIR filter process, generate another road signal;

(5) by first group of weight vectorsThe two paths of signals that step (4) is obtained addsPower synthetic output, obtains the H polarization pulse of first transmitting during a complete impulse ejectionEcho-signal;

(6) by second group of weight vectorsThe two paths of signals that step (4) is obtained addsThe synthetic output of power, obtains the returning of V polarization pulse of second transmitting during a complete impulse ejectionRipple signal.

2. the polar echo separation side of a kind of wide cut complete polarization satellite-borne SAR according to claim 1Method, is characterized in that: two described H polarization pulse and V that launch successively in described step (2)The ripple of polarization pulse reaches vector v₁With v₂While being, become, its expression formula is respectivelyWithK the element that ripple reaches in vector can be expressed asWherein, i=1,2, i=1 interval scale H polarization pulse, i=2Interval scale V polarization pulse;

Wherein λ is that wavelength, d are that pitching is to receive path interval, θ_i(τ) be H polarization pulse, wherein i=1;Or the echo of V polarization pulse is at Bo Dajiao corresponding to τ moment, wherein i=2; Its account form by asLower step is carried out:

(a) calculate corresponding instantaneous at the echo of τ moment H polarization pulse by formula R (τ)=c τ/2Oblique distance R; Wherein c is the light velocity; The oblique distance of V polarization pulse echo can be expressed as R'(τ)=c (τ-T)/2, itsMiddle T is two transmission intervals between polarization pulse;

(b) according to the instantaneous oblique distance R (τ) calculating in step (a), according to formulaSolve the instantaneous substar visual angle of H polarization pulse echoα (τ), wherein R_eFor earth radius, H is satellite orbital altitude;

(c) according to antenna pitching to normal direction substar visual angle α_cAnd the wink calculating in step (b)Shi Huibo substar visual angle α (τ), utilizes formula θ (τ)=α (τ)-α_cTry to achieve the corresponding ripple of echo and reach angle.

3. the polar echo separation side of a kind of wide cut complete polarization satellite-borne SAR according to claim 1Method, is characterized in that: the FIR wave filter in described step (4) is one 8 rank Time-Delay Filters, bowsFace upward to k the corresponding delay volume of receive path and beWherein K_rFor transmittingThe linear frequency modulation rate of pulse,For passing through scene center moment τ in pulse_cIt is right that Shi Bo reaches angle θ (τ)Distance is to the single order local derviation of fast time τ.

4. the polar echo separation side of a kind of wide cut complete polarization satellite-borne SAR according to claim 1Method, is characterized in that: the weight vectors in described step (5)For matrix N_e[(V')^HV']^-1'sThe first row, wherein, (V')^HV' is obtained by following formula: ${\left(V^{\′}\right)}^H{V}^{\′}=\left[\begin{array}{cc}\underset{k=1}{\overset{N_e}{\Σ}}{f^{\′}}_{11k}\left(\mathrm{\τ}\right)& \underset{k=1}{\overset{N_e}{\Σ}}{f^{\′}}_{12k}\left(\mathrm{\τ}\right)\\ \underset{k=1}{\overset{N_e}{\Σ}}{f^{\′}}_{21k}\left(\mathrm{\τ}\right)& \underset{k=1}{\overset{N_e}{\Σ}}{f^{\′}}_{22k}\left(\mathrm{\τ}\right)\end{array}\right],$ Element f' shown in matrix_ijk(τ) can be expressed as ${f^{\′}}_{ijk}\left(\mathrm{\τ}\right)=\exp \{j\frac{2\mathrm{\π}}{\mathrm{\λ}}(k-1)d\·\{sin\[{\mathrm{\θ}}_j(\mathrm{\τ}+D_k)\]-sin\[{\mathrm{\θ}}_i(\mathrm{\τ}+D_k)\]\left\}\right\},$ i,j＝1,2,k∈[1,N_e]，θ₁GenerationThe Bo Dajiao of table H polarization pulse, θ₂Represent the Bo Dajiao of V polarization pulse.

5. the polar echo separation side of a kind of wide cut complete polarization satellite-borne SAR according to claim 1Method, is characterized in that: the weight vectors in described step (5) and (6)For matrixN_e[(V')^HV']^-1The second row, wherein, (V')^HV' is obtained by following formula:

${\left(V^{\′}\right)}^H{V}^{\′}=\left[\begin{array}{cc}\underset{k=1}{\overset{N_e}{\Σ}}{f^{\′}}_{11k}\left(\mathrm{\τ}\right)& \underset{k=1}{\overset{N_e}{\Σ}}{f^{\′}}_{12k}\left(\mathrm{\τ}\right)\\ \underset{k=1}{\overset{N_e}{\Σ}}{f^{\′}}_{21k}\left(\mathrm{\τ}\right)& \underset{k=1}{\overset{N_e}{\Σ}}{f^{\′}}_{22k}\left(\mathrm{\τ}\right)\end{array}\right],$ Element f' shown in matrix_ijk(τ) can be expressed as ${f^{\′}}_{ijk}\left(\mathrm{\τ}\right)=\exp \{j\frac{2\mathrm{\π}}{\mathrm{\λ}}(k-1)d\·\{sin\[{\mathrm{\θ}}_j(\mathrm{\τ}+D_k)\]-sin\[{\mathrm{\θ}}_i(\mathrm{\τ}+D_k)\]\left\}\right\},$ i,j＝1,2,k∈[1,N_e]，θ₁GenerationThe Bo Dajiao of table H polarization pulse, θ₂Represent the Bo Dajiao of V polarization pulse.