CN103885052A - Polarization echo separation method of wide-range complete-polarization satellite-borne SAR - Google Patents

Abstract

Disclosed is a polarization echo separation method of wide-range complete-polarization satellite-borne SAR. The wide-range complete-polarization satellite-borne SAR is a novel system in which H polarization pulses and V polarization pulses are sequentially emitted within a pulse repeating interval, then echoes are received through a double-polarization passage, and therefore four polarization components are obtained. The complete-polarization SAR does not increase the repeat frequency of the system, so that a wider swath can be obtained. However, in order to improve the performance, the echoes of different polarization pulses need to be separated firstly. The polarization echo separation method is modified based on a traditional LCMV algorithm, the traditional algorithm is split, FTR filtering is led in between the two split steps, and then the second step is correspondingly modified and adjusted. Polarization echo separation is achieved according to the method, on one hand, isolation of the different polarization echoes meets the application requirement, and on the other hand, on-satellite calculation amount does not need to be increased too much, and the engineering realization difficulty is lowered.

Description

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

Technical field

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

Background technology

Receive echo by launching different polarization pulses and dual polarization passage, complete polarization satellite-borne SAR can obtain the scattered information of each resolution element under difference polarization combination, and this contributes to further to understand the backscattering characteristic of target.Therefore, than single polarization SAR, complete polarization SAR can provide the more target information of horn of plenty, contributes to determine target scattering mechanism, promotes the detection discriminator ability of target and suppressing the noise jamming receiving.Due to the introducing of complete polarization technology, the application of SAR is greatly widened.By full polarimetric SAR, we can extract more information, and these information have in fields such as agricultural monitoring, hydro_geography, city planning, Disaster Assessment and military surveillances the effect that cannot estimate.

Present stage, a series of complete polarization Spaceborne SAR System were in orbit (as the TerraSAR-X of moral aerospace, the RADARSAT-2 of space agency of Canada etc.) be all that the mode that adopts alternate emission H/V polarization pulse and dual polarization passage reception echo to combine realizes complete polarization earth observation imaging, the transmission interval of two kinds of polarization pulses is pulse recurrence interval (PRI, Pulse repetition interval), as shown in accompanying drawing 1 (a).This polarization mode need promote one times to avoid the deterioration of azimuth ambiguity by system PRF, thereby causes imaging fabric width to reduce half, has reduced and has heavily visited observing frequency, and this is also the maximum drawback of current complete polarization satellite-borne SAR.

For overcoming the above problems, moral aerospace DLR has proposed a kind of novel complete polarization satellite-borne SAR system in 2008, this system two kinds of polarization pulses of transmitting (shown in accompanying drawing 1 (b) with shown in accompanying drawing 2) continuously during pulsatile once transmitting, receive by dual polarization passage again at receiving end, just can obtain in theory whole four kinds of polarization components, needn't improve again system PRF and realize complete polarization observation.After this system proposes, both at home and abroad its feasibility in theory is unanimously approved, but thought that the biggest obstacle of this system Project Realization is different polarization pulse echos aliasings in time simultaneously.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, therefore 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 the article of a piece " a kind of new multipolarization satellite-borne SAR working method research " by name and has studied and address this problem on publication " Chinese science E periodical ", method described in literary composition need to complete Range compress processing on star, then carries out to range gate one by one zero again and falls into inhibition processing.Owing to will complete Range compress on star, therefore greatly increase the operand on star, very high to resource requirement on star, be difficult to through engineering approaches and realize.In a word, by the end of at present, also on open source literature, do not see 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 the echo Aliasing Problem of New System complete polarization satellite-borne SAR, the present invention proposes a kind of novel pitching and form method to digital beam.This method is by linear restriction minimum variance (the Linear Constraint Minimum Variance that tradition sensing at zero point processing is adopted, LCMV) algorithm improves, upwards form two digital reception beams in pitching and realize airspace filter (accompanying drawing 3), just completed the separation to two kinds of polar echos at echo reception period.

Technical solution of the present invention is:

A kind of polar echo separation method of wide cut complete polarization satellite-borne SAR, described polar echo is H polarization pulse and the corresponding echo of V polarization pulse of launching successively in a pulse recurrence interval, and these two kinds of echoes are back to receiver from different positions, visual angle in echo receiver window simultaneously, thus in time domain aliasing; The step of described separation method is as follows:

(1) to Planar Phased Array Antenna pitching upwards in each receiving cable received echo carry out successively low noise amplification, down coversion and ADC sampling processing, high frequency analog signals corresponding original echo is become to low-frequency digital signal;

(2) utilize the real-time ripple of described H polarization pulse and V polarization pulse to reach vector v ₁with v ₂the low-frequency digital signal respectively step (1) being obtained is weighted processing, wherein pitching to the low-frequency digital signal of k receiving cable respectively by v ₁with v ₂k element w _1kwith w _2kweighting, k is positive integer, and k ∈ [1, N _e], N _efor the number of receiving cable;

(3) by pitching to two-way in each receiving cable through different weights v ₁with v ₂the signal of weighting carries out corresponding FIR filtering processing;

(4) the process weight vectors v of each receiving cable output ₁and the synthetic output that adds up of the signal phasor of FIR filter process, generate a road signal; The process weight vectors v of each receiving cable output ₂and the synthetic output that adds up of the signal phasor of FIR filter process, generate another road signal;

(5) by first group of weight vectors

the two paths of signals that step (4) is obtained is weighted synthetic output, obtains the echoed signal of the H polarization pulse of first transmitting during a complete impulse ejection;

(6) by second group of weight vectors

the two paths of signals that step (4) is obtained is weighted synthetic output, obtains the echoed signal of the V polarization pulse of second transmitting during a complete impulse ejection.

In described step (2) two the described H polarization pulse of transmitting and the ripple of V polarization pulse reach vector v successively ₁with v ₂while being, become, its expression formula is respectively

with k the element that ripple reaches in vector can be expressed as $W_{\mathrm{ik}}=\exp \{\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="HDA0000481714840000012.png,HDA0000481714840000013.png"\; state="\{\{state\}\}">j</figure-callout>}\frac{2\mathrm{\&pi;}}{\mathrm{\&lambda;}}(k-1)d\&CenterDot;\sin [{\mathrm{\&theta;}}_i\left(\mathrm{\&tau;}\right)\left]\right\}(i=\mathrm{1,2}),$ I=1 interval scale H polarization pulse, i=2 interval scale V polarization pulse;

Wherein λ is that wavelength, d are that pitching is to receiving cable interval, θ _i(τ) be the echo of H polarization pulse (i=1) or V polarization pulse (i=2) at Bo Dajiao corresponding to τ moment, its account form is carried out as follows:

(a) the corresponding instantaneous oblique distance R of echo calculating at τ moment H polarization pulse by formula R (τ)=c τ/2; Wherein c is the light velocity; The oblique distance of V polarization pulse echo can be expressed as R'(τ)=c (τ-T)/2, wherein 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 α (τ) of H polarization pulse echo, wherein R _efor earth radius, H is satellite orbital altitude;

(c) according to antenna pitching to normal direction substar visual angle α _cand the instantaneous echo substar visual angle α (τ) calculating in step (b), utilize 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 to k the corresponding delay volume of receiving cable is

wherein K _rfor exomonental linear frequency modulation rate,

for passing through scene center moment τ in pulse _cshi Bo reaches angle θ (τ) and adjusts the distance to the single order local derviation of fast time τ.

Weight vectors in described 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:

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

${f^{\&prime;}}_{\mathrm{ilk}}\left(\mathrm{\&tau;}\right)=\exp \{\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="HDA0000481714840000012.png,HDA0000481714840000013.png"\; state="\{\{state\}\}">j</figure-callout>}\frac{2\mathrm{\&pi;}}{\mathrm{\&lambda;}}(k-1)d\&CenterDot;\{\sin \left[{\mathrm{\&theta;}}_j(\mathrm{\&tau;}+D_k)\right]-\sin \left[{\mathrm{\&theta;}}_i(\mathrm{\&tau;}+D_k)\right]\left\}\right\},$ I, j=1,2, k ∈ [1, N _e], θ ₂represent the Bo Dajiao of V polarization pulse, θ ₁represent 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 the impact of pulse ductility on separating property.Because subpulse all has certain pulsewidth, it is all that in a certain particular moment, it all can cover certain region on ground, can only realize sunken suppress (the interference subpulse) of maximum gain reception (signal subspace pulse)/the darkest zero to the center of institute overlay area and point to method traditional zero point, receive and cannot realize the gain identical with center to other region, therefore cause isolation poor, and the present invention can promote isolation about 10dB, make 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 introduced 8 rank FIR filtering (shown in accompanying drawing 4) between two step weightings are processed.This compresses with advanced row distance, range gate is done zero point and pointed to compared with the echo free flow process of processing one by one again, has greatly reduced the system architecture on star and has processed accordingly operand, is conducive to through engineering approaches and realizes.

Accompanying drawing explanation

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

Embodiment

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

Because two kinds of polaron pulses (two kinds of polarization pulses of H and V) of New System wide cut complete polarization satellite-borne SAR are launched successively, therefore in any time of echo receiver window, the echo of two kinds of polarization pulses of H and V can be back to receiver from different visual angles respectively, and the earth's surface information (shown in accompanying drawing 3) that contains zones of different.According to this difference, we can utilize digital beam to form (DBF) technology to form the received beam of two real time scans and receive respectively at receiving end the echo of H and V polarization pulse, and each wave beam has 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 system of equations:

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

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

Wherein i, j ∈ [1,2] (as subscript i, j=1 represents that correlation parameter is the correlation parameter of H polarization pulse, i, j=2 represents that parameter is the correlation parameter of V polarization pulse), symbol () ^hrepresent conjugate transpose, w _irepresent to form the weight vectors of i beamlet, N _erepresent pitching to the sub-aperture number of reception (receiving cable quantity), v _iand v _jrepresent respectively i and j the corresponding steering vector of subpulse (steering vecotr), they can be expressed as respectively

$v_i={[1,\exp \{\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="HDA0000481714840000012.png,HDA0000481714840000013.png"\; state="\{\{state\}\}">j</figure-callout>}\frac{2\mathrm{\&pi;}}{\mathrm{\&lambda;}}d\sin \left({\mathrm{\&theta;}}_i\right)\},...,\exp \{\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="HDA0000481714840000012.png,HDA0000481714840000013.png"\; state="\{\{state\}\}">j</figure-callout>}\frac{2\mathrm{\&pi;}}{\mathrm{\&lambda;}}(N_e-1)d\sin \left({\mathrm{\&theta;}}_i\right)\left\}\right]}^T---\left(2.1\right)$

With

$v_i={[1,\exp \{\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="HDA0000481714840000012.png,HDA0000481714840000013.png"\; state="\{\{state\}\}">j</figure-callout>}\frac{2\mathrm{\&pi;}}{\mathrm{\&lambda;}}d\sin \left({\mathrm{\&theta;}}_i\right)\},...,\exp \{\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="HDA0000481714840000012.png,HDA0000481714840000013.png"\; state="\{\{state\}\}">j</figure-callout>}\frac{2\mathrm{\&pi;}}{\mathrm{\&lambda;}}(N_e-1)d\sin \left({\mathrm{\&theta;}}_i\right)\left\}\right]}^T---(2.2)$

Wherein () ^tfor transposition symbol, d be pitching to interval, sub-aperture, λ is wavelength, θ _iwith θ _jrepresent that respectively i the pitching corresponding with the individual sub-pulse echo of j is to normal direction deviation angle (off-boresight angle), ripple reaches angle.Because subpulse is advanced on ground, therefore steering vector v _iand v _jwhile being, become, this has also 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=[v ₁,v ₂] (3)

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

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

Wherein e _ibe the i row of one 2 × 2 unit matrixs.By separating above system of equations, we can draw and form i weight vectors w that receives beamlet _ifor

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

Wherein S _tnfor the covariance matrix (spectral matrix) of receiver noise.This noise can be modeled as white noise and power is

s _tncan be write as

$S_{\mathrm{tn}}={\mathrm{\&sigma;}}_{\mathrm{<figure-callout\; id="2"\; label="tn"\; filenames="HDA0000481714840000012.png,HDA0000481714840000013.png"\; state="\{\{state\}\}">tn</figure-callout>}}^2\&CenterDot;I_{N_e\&times;N_e}---\left(6\right)$

Wherein

be a N _ethe unit matrix of dimension.Formula (6) is brought into formula (5),

can be reduced to

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

But, because pulse has certain pulsewidth, therefore it has certain ductility on the ground, i that utilizes the represented weight vectors of formula (7) to form receives beamlet and can only fall into a certain position formation maximum gain/the darkest zero, all the other positions cannot obtain the receiving gain identical with center, and this can cause the problem that degree of separation is inadequate in the later stage.

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

(1) synthetic traditional LC MV weighting represented formula (7) processing is split into two steps.Two row vectors that the first step is comprised by the matrix V H synthetic output of original signal weighting to array received to pitching respectively; Second step is to utilize row vector

the two paths of signals that the first step is exported is weighted synthetic.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, after completing, the first step in each passage, introduced FIR filtering processing in pitching, the filter system response function in k sub-aperture

$H_{\mathrm{FIR}\_k}\left(f\right)=\exp \left\{\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="HDA0000481714840000012.png,HDA0000481714840000013.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;}\frac{(k-1)f_0}{K_r}f\right\}---\left(8\right)$

Wherein K _rfor exomonental FM signal, (d be pitching to interval, sub-aperture, λ is wavelength, for saving partial differential for distance to one of fast time τ in echo window center moment echo visual angle).H _{fIR_k}(f) phase place is the linear function of frequency f, the delay process in the corresponding time domain of this ssystem transfer function, and 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, the vector of the second step weighting processing after LCMV is split

do corresponding correction, become

guarantee relevant the synthesizing between signal, made finally to obtain optimum echo free effect.

Note:

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

Wherein ${f^{\&prime;}}_{\mathrm{ilk}}\left(\mathrm{\&tau;}\right)=\exp \{\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="HDA0000481714840000012.png,HDA0000481714840000013.png"\; state="\{\{state\}\}">j</figure-callout>}\frac{2\mathrm{\&pi;}}{\mathrm{\&lambda;}}(k-1)d\&CenterDot;\{\sin \left[{\mathrm{\&theta;}}_j\left(\mathrm{\&tau;}\right)\right]-\sin \left[{\mathrm{\&theta;}}_i(\mathrm{\&tau;}+D_k)\right]\left\}\right\},$ And (V') ^hv' is

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

Wherein ${f^{\&prime;}}_{\mathrm{ilk}}\left(\mathrm{\&tau;}\right)=\exp \{\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="HDA0000481714840000012.png,HDA0000481714840000013.png"\; state="\{\{state\}\}">j</figure-callout>}\frac{2\mathrm{\&pi;}}{\mathrm{\&lambda;}}(k-1)d\&CenterDot;\{\sin \left[{\mathrm{\&theta;}}_j(\mathrm{\&tau;}+D_k)\right]-\sin \left[{\mathrm{\&theta;}}_i(\mathrm{\&tau;}+D_k)\right]\left\}\right\},$ In formula $D_k=\frac{(k-1)}{K_r}{f}_0.$

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

(1) utilize the first step that point in processing the traditional zero point being split out to be weighted processing to digital echo signal;

(2) do corresponding time delay processing by each pitching to receiving the signal after to step (1) weighting of corresponding FIR wave filter in sub-aperture;

(3) last, the signal that in pointing to and process the zero point after utilization improves, second step obtains step (2) does the synthetic processing of corresponding weighting, 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 is processed block diagram as shown in Figure 6, and step is as follows:

(1) to Planar Phased Array Antenna pitching upwards in each receiving cable received echo carry out successively low noise amplification, down coversion and ADC sampling processing, high frequency analog signals corresponding original echo is become to low-frequency digital signal;

(2) utilize the real-time ripple of described H polarization pulse and V polarization pulse to reach vector v ₁with v ₂the low-frequency digital signal respectively step (1) being obtained is weighted processing, wherein pitching to the low-frequency digital signal of k receiving cable respectively by v ₁with v ₂k element w _1kwith w _2kweighting, k is positive integer, and k ∈ [1, N _e], N _efor the number of receiving cable;

Described two described H polarization pulses of launching successively and the ripple of V polarization pulse reach vector v ₁with v ₂while being, become, its expression formula is respectively

k the element that ripple reaches in vector can be expressed as $W_{\mathrm{ik}}=\exp \{\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="HDA0000481714840000012.png,HDA0000481714840000013.png"\; state="\{\{state\}\}">j</figure-callout>}\frac{2\mathrm{\&pi;}}{\mathrm{\&lambda;}}(k-1)d\&CenterDot;\sin [{\mathrm{\&theta;}}_i\left(\mathrm{\&tau;}\right)\left]\right\}(i=\mathrm{1,2}),$ I=1 interval scale H polarization pulse, i=2 interval scale V polarization pulse;

Wherein λ is that wavelength, d are that pitching is to receiving cable interval, θ _i(τ) be that i sub-pulse echo (i=1 is the pulse of H polaron, and i=2 is the pulse of V polaron) at Bo Dajiao corresponding to τ moment, carry out as follows by its account form:

(a) the corresponding instantaneous oblique distance R of echo calculating at τ moment H polarization pulse by formula R (τ)=c τ/2; Wherein c is the light velocity; The oblique distance of V polarization pulse echo can be expressed as R'(τ)=c (τ-T)/2, wherein 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 α (τ) of H polarization pulse echo, wherein R _efor earth radius, H is satellite orbital altitude;

(c) according to antenna pitching to normal direction substar visual angle α _cand the instantaneous echo substar visual angle α (τ) calculating in step (b), utilize 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 receiving cable through different weights v ₁with v ₂the signal of weighting carries out corresponding FIR filtering processing;

Described FIR wave filter is one 8 rank Time-Delay Filters, and pitching to k the corresponding delay volume of receiving cable is wherein K _rfor exomonental linear frequency modulation rate,

for passing through scene center moment τ in pulse _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 receiving cable output ₁and the synthetic output that adds up of the signal phasor of FIR filter process, generate a road signal; The process weight vectors v of each receiving cable output ₂and the synthetic output that adds up of the signal phasor of FIR filter process, generate another road signal;

(5) by first group of weight vectors

the two paths of signals that step (4) is obtained is weighted synthetic output, obtains the echoed signal of the H polarization pulse of first transmitting during a complete impulse ejection;

(6) by second group of weight vectors

the two paths of signals that step (4) is obtained is weighted synthetic output, obtains the echoed signal of the V polarization pulse of second transmitting during a complete impulse ejection.

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:

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

${f^{\&prime;}}_{\mathrm{ilk}}\left(\mathrm{\&tau;}\right)=\exp \{\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="HDA0000481714840000012.png,HDA0000481714840000013.png"\; state="\{\{state\}\}">j</figure-callout>}\frac{2\mathrm{\&pi;}}{\mathrm{\&lambda;}}(k-1)d\&CenterDot;\{\sin \left[{\mathrm{\&theta;}}_j(\mathrm{\&tau;}+D_k)\right]-\sin \left[{\mathrm{\&theta;}}_i(\mathrm{\&tau;}+D_k)\right]\left\}\right\},$ I, j=1,2, k ∈ [1, N _e], θ ₂represent the Bo Dajiao of V polarization pulse, θ ₁represent the Bo Dajiao of H polarization pulse.

The content not being described in detail in instructions of the present invention belongs to professional and technical personnel in the field's known technology.

Claims (5)

1. the polar echo separation method of a wide cut complete polarization satellite-borne SAR, described polar echo is H polarization pulse and the corresponding echo of V polarization pulse of launching successively in a pulse recurrence interval, these two kinds of echoes are back to receiver from different positions, visual angle in echo receiver window simultaneously, thus in time domain aliasing; It is characterized in that: the step of described separation method is as follows:

(1) to Planar Phased Array Antenna pitching upwards in each receiving cable received echo carry out successively low noise amplification, down coversion and ADC sampling processing, high frequency analog signals corresponding original echo is become to low-frequency digital signal;

(2) utilize the real-time ripple of described H polarization pulse and V polarization pulse to reach vector v ₁with v ₂the low-frequency digital signal respectively step (1) being obtained is weighted processing, wherein pitching to the low-frequency digital signal of k receiving cable respectively by v ₁with v ₂k element w _1kwith w _2kweighting, k is positive integer, and k ∈ [1, N _e], N _efor the number of receiving cable;

(3) by pitching to two-way in each receiving cable through different weights v ₁with v ₂the signal of weighting carries out corresponding FIR filtering processing;

(4) the process weight vectors v of each receiving cable output ₁and the synthetic output that adds up of the signal phasor of FIR filter process, generate a road signal; The process weight vectors v of each receiving cable output ₂and the synthetic output that adds up of the signal phasor of FIR filter process, generate another road signal;

(5) by first group of weight vectors

the two paths of signals that step (4) is obtained is weighted synthetic output, obtains the echoed signal of the H polarization pulse of first transmitting during a complete impulse ejection;

(6) by second group of weight vectors

the two paths of signals that step (4) is obtained is weighted synthetic output, obtains the echoed signal of the V polarization pulse of second transmitting during a complete impulse ejection.

2. the polar echo separation method of a kind of wide cut complete polarization satellite-borne SAR according to claim 1, is characterized in that: in described step (2) two the described H polarization pulse of transmitting and the ripple of V polarization pulse reach vector v successively ₁with v ₂while being, become, its expression formula is respectively with

k the element that ripple reaches in vector can be expressed as

$W_{\mathrm{ik}}=\exp \{j\frac{2\mathrm{\&pi;}}{\mathrm{\&lambda;}}(k-1)d\&CenterDot;\sin [{\mathrm{\&theta;}}_i\left(\mathrm{\&tau;}\right)\left]\right\}(i=\mathrm{1,2}),$ I=1 interval scale H polarization pulse, i=2 interval scale V polarization pulse;

Wherein λ is that wavelength, d are that pitching is to receiving cable interval, θ _i(τ) be the echo of H polarization pulse (i=1) or V polarization pulse (i=2) at Bo Dajiao corresponding to τ moment, its account form is carried out as follows:

(a) the corresponding instantaneous oblique distance R of echo calculating at τ moment H polarization pulse by formula R (τ)=c τ/2; Wherein c is the light velocity; The oblique distance of V polarization pulse echo can be expressed as R'(τ)=c (τ-T)/2, wherein 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 α (τ) of H polarization pulse echo, wherein R _efor earth radius, H is satellite orbital altitude;

(c) according to antenna pitching to normal direction substar visual angle α _cand the instantaneous echo substar visual angle α (τ) calculating in step (b), utilize formula θ (τ)=α (τ)-α _ctry to achieve the corresponding ripple of echo and reach angle.

3. how much echo free methods of a kind of wide cut complete polarization satellite-borne SAR according to claim 1, is characterized in that: the FIR wave filter in described step (3) is one 8 rank Time-Delay Filters, and pitching to k the corresponding delay volume of receiving cable is

wherein K _rfor exomonental linear frequency modulation rate, for passing through scene center moment τ in pulse _cshi Bo reaches angle θ (τ) and adjusts the distance to the single order local derviation of fast time τ.

4. how much echo free methods of a kind of wide cut complete polarization satellite-borne SAR according to claim 1, is characterized in that: the weight vectors in described step (5)

for matrix N _e[(V') ^hv'] ^-1the first row, wherein, (V') ^hv' is obtained by following formula: ${\left(v^{\&prime;}\right)}^H{v}^{\&prime;}=\left[\begin{array}{cc}\underset{k=1}{\overset{N_e}{\mathrm{\&Sigma;}}}{f^{\&prime;}}_{11k}\left(\mathrm{\&tau;}\right)& \underset{k=1}{\overset{N_e}{\mathrm{\&Sigma;}}}{f^{\&prime;}}_{12k}\left(\mathrm{\&tau;}\right)\\ \underset{k=1}{\overset{N_e}{\mathrm{\&Sigma;}}}{f^{\&prime;}}_{21k}\left(\mathrm{\&tau;}\right)& \underset{k=1}{\overset{N_e}{\mathrm{\&Sigma;}}}{f^{\&prime;}}_{22}k\left(\mathrm{\&tau;}\right)\end{array}\right],$ Element f' shown in matrix _ijk(τ) can be expressed as

${f^{\&prime;}}_{\mathrm{ilk}}\left(\mathrm{\&tau;}\right)=\exp \{j\frac{2\mathrm{\&pi;}}{\mathrm{\&lambda;}}(k-1)d\&CenterDot;\{\sin \left[{\mathrm{\&theta;}}_j(\mathrm{\&tau;}+D_k)\right]-\sin \left[{\mathrm{\&theta;}}_i(\mathrm{\&tau;}+D_k)\right]\left\}\right\},$ I, j=1,2, k ∈ [1, N _e], θ ₁represent the Bo Dajiao of H polarization pulse, θ ₂represent the Bo Dajiao of V polarization pulse.

5. how much echo free methods of a kind of wide cut complete polarization satellite-borne SAR according to claim 1, is characterized in that: the weight vectors in described step (5) and (6)

for matrix

N _e[(V') ^hv'] ^-1the second row, wherein, (V') ^hv' is obtained by following formula:

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

${f^{\&prime;}}_{\mathrm{ilk}}\left(\mathrm{\&tau;}\right)=\exp \{j\frac{2\mathrm{\&pi;}}{\mathrm{\&lambda;}}(k-1)d\&CenterDot;\{\sin \left[{\mathrm{\&theta;}}_j(\mathrm{\&tau;}+D_k)\right]-\sin \left[{\mathrm{\&theta;}}_i(\mathrm{\&tau;}+D_k)\right]\left\}\right\},$ I, j=1,2, k ∈ [1, N _e], θ ₁represent the Bo Dajiao of H polarization pulse, θ ₂represent the Bo Dajiao of V polarization pulse.

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