CN106291547A - Doppler ambiguity component Adaptive Suppression method based on antenna radiation pattern auxiliary - Google Patents

Abstract

The invention discloses a kind of doppler ambiguity component Adaptive Suppression method based on antenna radiation pattern auxiliary, by the range Doppler numeric field data after calculating Doppler ambiguity-resolution, and it is carried out orientation synthetic aperture imaging, it is thus achieved that the High Resolution SAR Images after Doppler ambiguity-resolution.It can effectively suppress major and minor lobe obscuring component, it is achieved high resolution wide swath airborne synthetic aperture radar (SAR) Doppler ambiguity-resolution.Emulation experiment shows: compared with not considering to suppress secondary lobe obscuring component, after using solution doppler ambiguity of the present invention, point target imaging orientation peak sidelobe ratio performance improves about 9.6dB.

Description

Doppler ambiguity component Adaptive Suppression method based on antenna radiation pattern auxiliary

Technical field

The present invention relates to airborne multichannel SAR wide-scene survey field, be specifically related to a kind of based on antenna radiation pattern auxiliary Doppler ambiguity component Adaptive Suppression method.

Background technology

In airborne synthetic aperture radar imaging, for solving the contradiction between wide swath and orientation high-resolution, domestic Outer scholar has mainly done a lot of research work in terms of two, is on the one hand SAR ambiguity solution treatment technology, is on the other hand research and development More flexible new SAR system；Generally in SAR system generally by relatively low pulse recurrence frequency (PRF) with the wider scope of guarantee Interior coverage rate, but bearing signal is fuzzy, and therefore ambiguity solution is the problem that SAR imaging have to solve.But, this algorithm is also Not taking into account the echo-signal that antenna side lobe receives, it also will produce corresponding doppler ambiguity component, and after causing ambiguity solution Average minor level raise.Therefore, the interference of suppression secondary lobe doppler ambiguity component is that imaging engineering is surveyed and drawn in high-resolution broadband The problem that realization have to solve.

Tradition frequency spectrum reconfiguration algorithm only considers that antenna main lobe receives signal, have ignored the impact of secondary lobe obscuring component, causes The hydraulic performance decline of frequency spectrum reconfiguration algorithm, will produce orientation false target time serious.In recent years, domestic and international scientific research personnel advocates Many ways be use ultralow side lobe array antenna to eliminate the interference of secondary lobe obscuring component, but in antenna works is applied, super The design of low sidelobe antenna and realization all face the biggest technical barrier, and research cost is high.Additionally, Chinese scholars has been ground Study carefully the technology such as multiple secondary lobe interference mitigation technology, such as secondary lobe cancellation, weighting counteracting, but above-mentioned technology application background has all had Particularity, is not particularly suited for multichannel SAR orientation ambiguity solution.

Summary of the invention

The technical problem to be solved is for defect involved in background technology, it is provided that a kind of based on sky The doppler ambiguity component Adaptive Suppression method of line directional diagram auxiliary, on the one hand solves tradition frequency spectrum reconfiguration algorithm and only considers Main lobe signal and ignore secondary lobe obscuring component problem, on the other hand effectively prevent when tradition solves azimuth ambiguity under systematic error The signal cancellation of ADBF spatial domain covariance matrix and the problem of target guiding vector mismatch.

The present invention solves above-mentioned technical problem by the following technical solutions:

Doppler ambiguity component Adaptive Suppression method based on antenna radiation pattern auxiliary, comprises the steps:

Step 1), reception channel signal N number of to airborne synthetic aperture radar carries out distance to pulse compression respectively, and according to Below equation travel direction dimension fast Fourier transform, it is thus achieved that the distance-Doppler numeric field data of each reception passage:

S_n(τ, f)=FFT_t[S_n(τ,t)]

Wherein t be orientation to the time, τ is that distance is to time, S_n(τ is t) that the n-th channel distance is believed after pulse compression Number, FFT_tRepresent that f represents that orientation is to Doppler frequency domain, S about orientation Fourier transformation on time t_n(τ is f) n-th Channel distance-Doppler domain data；

Step 2), for each distance unit, for each doppler cells that this distance unit is corresponding, carry out as Lower calculating:

Step 2.1), use NSIE technology to estimate the DoA value of each main lobe obscuring componentWherein Representing the DoA value of main lobe kth time obscuring component, K is the obscuring component number of main lobe, k=1 ..., K, the most each main lobe obscuring component Corresponding spatial domain steering vector is E=[e₁,...,e_k,...,e_K], wherein, e_kGuide for kth time main lobe obscuring component spatial domain and vow Amount,D is array element distance, and λ is signal wavelength, and N represents reception port number, subscript^TTable Show transposition operator；

Step 2.2), calculate each main lobe obscuring component with the relational expression of Space Angle according to following Doppler frequency corresponding Carrier aircraft real-time speed

${\hat{V}}_k=\frac{\mathrm{\λ}}{2\sin \left({\widehat{\mathrm{\β}}}_k\right)}{f}_q,k=1,...,K$

Wherein, f_qFor the Doppler frequency value that this doppler cells is corresponding, q represents that this doppler cells is this distance unit The corresponding q-th doppler cells in doppler cells set；

Step 2.3), to step 2.2) in carrier aircraft real-time speed corresponding to each main lobe obscuring component of obtaining be averaged Calculate, the carrier aircraft real-time speed estimated value obtained

$\hat{V}=\frac{{\hat{V}}_1+{\hat{V}}_2+...+{\hat{V}}_K}{K}$

Step 2.4), the DoA information of each secondary lobe obscuring component, the i.e. sine of its corresponding Space Angle is calculated according to equation below Value

$sin\left({\widehat{\mathrm{\θ}}}_m\right)=\frac{\mathrm{\λ}}{2\hat{V}}{f}_{SL,m}$

Wherein, f_SL,mIt is the Doppler frequency that the m time secondary lobe obscuring component is corresponding,Due to All there is a secondary lobe component main lobe both sides, m=± 1 ..., ± M, M are the natural number more than zero, and PRF is pulse recurrence frequency；

Step 2.5), according to the steering vector that the DoA information each secondary lobe obscuring component of calculating of each secondary lobe obscuring component is corresponding:

A=[a_-M,...,a_m,...,a_M]

Wherein, a_mIt is the m time secondary lobe obscuring component spatial domain steering vector,m =± 1 ..., ± M；

Step 2.6), build each the spatial domain association solving Doppler ambiguity-resolution corresponding to main lobe obscuring component according to below equation Variance matrix is:

σ in formula₀For the noise power-value loaded, I ∈ C^N×NUnit matrix, e_hIt is that the h time main lobe obscuring component is corresponding Spatial domain steering vector, subscript^HRepresent conjugate transpose operator, a_mFor the m time obscuring component spatial domain steering vector of secondary lobe, ρ_mIt is m The Amplitude Ration coefficient that secondary secondary lobe obscuring component is corresponding, is represented by:

${\mathrm{\ρ}}_m=\frac{b_m}{F},m=\±1,...,\±M$

Wherein b_mFor the antenna radiation pattern secondary lobe gain that m-th secondary lobe obscuring component is corresponding, F represents the master of antenna radiation pattern Lobe gain；

Step 2.7), extract the Adaptive beamformer weights W of each main lobe doppler ambiguity component_kFor:

$W_k=\frac{{\stackrel{\‾}{R}}^{-1}{e}_k}{B_k^H{\stackrel{\‾}{R}}^{-1}{B}_k}$

Step 2.8), utilize Adaptive beamformer weights W_kExtract each main lobe obscuring component p_{q_k}For:

$p_{q\_k}=W_k^{H}Z$

Wherein Z=[S₁(i,q),...,S_N(i,q)]^TRepresenting the vector expression of this doppler cells signal, i represents this The distance unit that doppler cells is corresponding is i-th distance unit；

Step 2.9), extract each main lobe obscuring component signal and be designated as P (i, k)=[p_{1_k},...,p_{Na_k}], wherein p_{q_k} The kth main lobe obscuring component extracted for q-th doppler cells, Na represents doppler cells number；

Step 3), for each distance unit, according to the different Doppler frequencies that each main lobe obscuring component is corresponding, will All main lobe obscuring component signal sequences arrange, and obtain data S (i, f after each distance unit Doppler ambiguity-resolution_a):

S(i,f_aP)=[(i, 1) ..., P (i, K)]

Wherein, f_aRepresent that the orientation after Doppler ambiguity-resolution is to Doppler frequency；

Step 4), obtain the distance-Doppler numeric field data after Doppler ambiguity-resolution, and it is carried out orientation synthetic aperture one-tenth Picture, it is thus achieved that the High Resolution SAR Images after Doppler ambiguity-resolution.

Step 2.1) in NSIE technology be my published technology: Mingwei Shen, Liu Yang, Di Wu, Daiyin Zhu.Multichannel SAR Wide-Swath Imaging based on Adaptive Removal of Azimuth Ambiguities,Remote Sense Letters,6(8),2015.8:628-636。

The present invention uses above technical scheme compared with prior art, has following technical effect that

The peak sidelobe ratio performance after secondary lobe its imaging of obscuring component amplitude coefficient is determined than not entering according to antenna radiation pattern The suppression of row secondary lobe obscuring component is compared, and improves about about 9.6dB.

Accompanying drawing explanation

Fig. 1 is positive side-looking stripmap SAR geometrical relationship schematic diagram；

Fig. 2 is Doppler ambiguity-resolution wave filter design flow diagram based on NSIT；

Fig. 3 is reception antenna direction schematic diagram；

Fig. 4 is reception diagram；

When Fig. 5 is to there is azimuth ambiguity, the orientation of point target is to profile azimuth ambiguity figure；

The actual two-dimensional spectrum relation of ground echo when Fig. 6 (a) is for existing azimuth ambiguity；

The preferable two-dimensional spectrum relation of ground echo when Fig. 6 (b) is for existing azimuth ambiguity；

Imaging azimuthal section after conventional ADBF scheme solution azimuth ambiguity is utilized when Fig. 7 (a) is not for considering secondary lobe obscuring component；

Imaging azimuthal section after context of methods solution azimuth ambiguity is utilized when Fig. 7 (b) is for considering secondary lobe obscuring component.

Detailed description of the invention

Below in conjunction with the accompanying drawings technical scheme is described in further detail:

The invention discloses doppler ambiguity component Adaptive Suppression method based on antenna radiation pattern auxiliary, airborne radar Geometric configuration is as it is shown in figure 1, carrier aircraft is flown along x-axis with speed V, and carrier aircraft flying height H, N number of even linear array divides along course straight line Cloth, it is stipulated that along navigation direction high order end array element for receiving and dispatching array element (being array element 1 in Fig. 1), remaining is for receiving array element.Assume aircraft Be in zero overhead when t=0, certain one time t, the position x=Vt of aircraft, then target to the oblique distance of the n-th passage is:

$\begin{array}{c}{R_n}^2\left(t\right)={R_0}^2+{(x+(n-1\left)d\right)}^2\\ ={R_0}^2+{(V\·t+(n-1\left)d\right)}^2\end{array},n=1,\mathrm{...},N---\left(1\right)$

Wherein R₀ ²=H²+y₀ ², H represents that aircraft altitude, d represent array element distance.

The echo model of the most each passage is:

$X_n(\mathrm{\τ},t)=\exp \[{\mathrm{j\πK}}_r{\mathrm{\τ}}^2\]\·\exp \[-j\frac{2\mathrm{\π}}{\mathrm{\λ}}\left(R_1\right(t)+R_n(t\left)\right)\],n=1,\mathrm{...},N---\left(2\right)$

K in formula_rRefer to launch pulse signal frequency modulation rate, τ represent distance to the time, t be orientation to the time, λ is wavelength.

Ground echo Doppler frequency f of carried SAR_dAnd the relation between azimuth angle theta is as shown in Figure 6, mathematical expression Formula is:

$f_d=\frac{2V}{\mathrm{\λ}}sin\left(\mathrm{\θ}\right)---\left(3\right)$

When there is the interference of secondary lobe obscuring component, owing to main lobe signal intensity is much larger than secondary lobe signal intensity, therefore NSIE still can be with the DoA of each obscuring component of main lobe.But for solving doppler ambiguity technology, all sides to be completely inhibited Position obscuring component, this just requires that method should be able to grasp the information of all blurred signals.Utilize fuzzy point of main lobe the most herein Amount DoA information inference goes out secondary lobe obscuring component DoA information, and then based on all obscuring component DoA information and main lobe and secondary lobe mould Stick with paste the amplitude coefficient design adaptive spatial filtering device of component, extract each main lobe obscuring component the most successively and reconstruct without fuzzy Doppler frequency spectrum.Fig. 2 gives the part signal handling process of the method.

Assume impact point to flight track (orientation to) vertical line with flight path point of intersection orientation to time t=0, existing with radar Array the n-th channel receiving signal X_n(τ, t) as a example by carry out distance dimension pulse compression, be:

$S_n(\mathrm{\τ},t)={\left\{{\mathrm{IFFT}}_{f_r}\right\{{\mathrm{FFT}}_{\mathrm{\τ}}\[X_n(\mathrm{\τ},t)\]\·{\mathrm{FFT}}_{\mathrm{\τ}}\[H_r\left(\mathrm{\τ}\right)\]\left\}\right\}}_{Nr\×Na}---\left(4\right)$

WhereinK_rFor launching the chirp rate of pulse signal；T be orientation to the time, τ be away from The descriscent time, Nr be distance to sampling number, Na is that orientation is to sampling number, FFT_τWithRepresent about distance to τ respectively Fourier transformation and about distance frequency domain inverse Fourier transform；By direction dimension fast Fourier transform can obtain distance- Doppler domain data, as a example by the n-th passage:

S_n(τ, f)=FFT_t[S_n(τ,t)]

S in formula_n(τ, f) is the n-th channel distance-Doppler domain data, and f is that orientation is to Doppler frequency, FFT_tRepresent and close The Fourier transformation on time t in orientation.

Main lobe obscuring component DoA estimates, utilization published technology in person: (Mingwei Shen, Liu Yang, Di Wu,Daiyin Zhu.Multichannel SAR Wide-Swath Imaging based on Adaptive Removal Of Azimuth Ambiguities, Remote Sense Letters, 6 (8), 2015.8:628-636.) middle employing NSIE skill Art estimates the DoA value of i-th distance each main lobe obscuring component of unit, as a example by q-th doppler cells, it is assumed that main lobe exists K obscuring component, the DoA value of its correspondence is respectivelyWhereinRepresent the DoA of main lobe kth time obscuring component Value, the spatial domain steering vector that the most each main lobe obscuring component is corresponding is respectively as follows:

E=[e₁,...,e_k,...,e_K]

Wherein e_kFor kth time main lobe obscuring component spatial domain steering vector,K= 1 ..., K, d are array element distance, and λ is signal wavelength, and N represents reception port number, subscript^TRepresent transposition operator.

Carrier aircraft real-time speed is estimated, at q-th doppler cells, as a example by kth time main lobe obscuring component, according to the most General Le frequency with the relational expression calculating carrier aircraft real-time speed of Space Angle is:

${\hat{V}}_k=\frac{\mathrm{\λ}}{2\sin \left({\widehat{\mathrm{\β}}}_k\right)}{f}_q,k=1,...,K$

Wherein, f_qFor the Doppler frequency value that q-th doppler cells is corresponding, all K main lobe obscuring component are estimated Carrier aircraft speed be averaged, the carrier aircraft real-time speed estimated value obtained is:

$\hat{V}=\frac{{\hat{V}}_1+{\hat{V}}_2+...+{\hat{V}}_K}{K}$

Therefore, the speed estimated is utilized to extrapolate secondary lobe obscuring component DoA value, at q-th doppler cells, according to as follows Formula calculates the sine value of the m time secondary lobe obscuring component correspondence Space Angle, it may be assumed that

$sin\left({\widehat{\mathrm{\θ}}}_m\right)=\frac{\mathrm{\λ}}{2\hat{V}}{f}_{SL,m}$

Wherein f_SL,mIt is the Doppler frequency that the m time secondary lobe obscuring component is corresponding,Due to All there is a secondary lobe component main lobe both sides, m=± 1 ..., ± M, desirable M=5 in engineer applied.

According to the steering vector of the DoA information all secondary lobe obscuring component of calculating of each secondary lobe obscuring component it is then:

A=[a_-M,...,a_m,...,a_M]

Wherein a_mIt is the m time secondary lobe obscuring component spatial domain steering vector,M= ±1,…,±M。

The spatial domain steering vector of major and minor lobe obscuring component can be obtained by above description, utilize the steering vector obtained Carry out Aided Design Doppler ambiguity-resolution wave filter, extract as a example by kth time main lobe obscuring component by q-th doppler cells, build The spatial domain covariance matrix solving Doppler ambiguity-resolution is:

${\stackrel{\‾}{R}}_k=\underset{h=1}{\overset{K}{\mathrm{\Σ}}}{e}_h{e}_h^H+\underset{m=-M}{\overset{M}{\mathrm{\Σ}}}{\mathrm{\ρ}}_m^2{a}_m{a}_m^H+{\mathrm{\σ}}_{0}I,h=1,...,K,h\≠k,m\≠0$

σ in formula₀For the noise power-value loaded, I ∈ C^N×NUnit matrix, e_hIt is that the h time main lobe obscuring component is corresponding Spatial domain steering vector, subscript^HRepresent conjugate transpose operator, a_mFor the m time obscuring component spatial domain steering vector of secondary lobe, ρ_mIt is m The Amplitude Ration coefficient that secondary secondary lobe obscuring component is corresponding, is represented by

${\mathrm{\ρ}}_m=\frac{b_m}{F},m=\±1,...,\±M$

Wherein b_mFor m-th secondary lobe amplitude, F represents main lobe amplitude, then extract kth main lobe doppler ambiguity component oneself Adapt to Wave beam forming (ADBF) weights W_kFor:

$W_k=\frac{{\stackrel{\‾}{R}}^{-1}{e}_k}{B_k^H{\stackrel{\‾}{R}}^{-1}{B}_k}.$

Utilize ADBF weights W_kThe q-th doppler cells kth main lobe obscuring component p extracted_{q_k}For:

$p_{q\_k}=W_k^{H}Z$

Wherein Z=[S₁(i,q),...,S_N(i,q)]^TRepresent the i-th distance unit q-th Doppler of N number of channel reception The vector expression of cell signal；

Last frequency spectrum reconfiguration, obscures by each doppler cells in i-th distance unit is extracted kth main lobe respectively Component signal is also designated as P (i, k)=[p_{1_k},...,p_{Na_k}], wherein p_{q_k}The kth main lobe extracted for q-th doppler cells Obscuring component, Na represents doppler cells number, then according to different Doppler frequencies corresponding to each main lobe obscuring component by institute There is main lobe obscuring component signal sequence to arrange, obtain data S (i, f after i-th distance unit Doppler ambiguity-resolution_a), it may be assumed that

S(i,f_aP)=[(i, 1) ..., P (i, K)]

Wherein f_aRepresent that the orientation after Doppler ambiguity-resolution is to Doppler frequency.

For each distance unit repetitive operation said method, the distance-Doppler after available Doppler ambiguity-resolution Numeric field data, and it is carried out orientation synthetic aperture imaging, the High Resolution SAR Images after Doppler ambiguity-resolution can be obtained.

Effectiveness below by Computer Simulation checking this patent.Mapping system orientation, airborne multichannel SAR broadband battle array Unit number N=4, main lobe obscuring component K=3.In emulation, ground is tieed up along distance to be spaced apart 3m drop target scattering point, target RCS Meet multiple Gauss distribution.Assuming that carrier aircraft speed existence ± 5m/s error, i.e. when setting carrier aircraft speed V=150m/s, it is actual Speed V=155m/s, concrete simulation parameter is as shown.

Parameter name	Parameter values
		Pulse recurrence frequency	210Hz
Transmitted signal bandwidth	60MHz
		Distance is to sample rate	75MHz
Array element distance	0.3m
		Length of synthetic aperture	360m
Carrier aircraft flying height	4472m
		Wavelength	0.03m

As shown in Figure 4, main lobe level exceeds 13.29dB than minor level to reception diagram, now can by formula above Know and calculating main lobe and the Amplitude Ratio coefficient of secondary lobe, be:

$\mathrm{\η}=\frac{c}{b}=\sqrt{\frac{{10}^{75.48}}{{10}^{62.22}}}=4$

I.e. principal subsidiary lobe amplitude coefficient calculated value is 0.25, is the amplitude coefficient of secondary lobe component.

Now provide three ambiguity of Doppler caused by orientation lack sampling, as it is shown in figure 5, in orientation to result in void The appearance of decoy.

For doppler ambiguity situation, main lobe is produced the DoA value of obscuring component by lack sampling to utilize NSIE to estimate, as above schemes Shown in 6.As Fig. 6 (a) represents that actual carrier aircraft runs the space-time two-dimensional spectral curve of echo-signal；The derivation of equation is passed through in Fig. 6 (b) expression Draw the ideal value of Space Angle.Compare actual value, a series of error problems that ideal value produces during have ignored aircraft motion, Thus cause steering vector mismatch problems.

This patent is the DoA information being estimated main lobe obscuring component by efficient NSIE, and utilizes this estimated value further The DoA of derivation secondary lobe obscuring component.And then utilize based on main lobe and the true DoA Aided Design airspace filter of secondary lobe obscuring component Utensil has real-time and accuracy, it is to avoid steering vector mismatch problems.But for avoiding band during solving doppler ambiguity interior Signal and the amplitude imbalance of out of band signal, in addition it is also necessary to combine antenna principal subsidiary lobe Amplitude Ration coefficient.

Fig. 7 gives employing peak sidelobe ratio and weighs secondary lobe in the case of considering secondary lobe obscuring component and not considering secondary lobe Obscuring component inhibition.The imaging results that when Fig. 7 (a) expression only considers main lobe obscuring component, Doppler frequency spectrum reconstruct obtains Figure；Fig. 7 (b) be based on antenna radiation pattern determine secondary lobe obscuring component amplitude coefficient carry out main lobe and secondary lobe obscuring component suppression after Imaging results figure.The simulation experiment result shows: the average peak secondary lobe after the imaging of Fig. 7 (a) than for 16.9dB, Fig. 7's (b) Average peak secondary lobe after imaging, than for 26.5dB, is compared Fig. 7 (a) and is improve about 9.6dB.Therefore, context of methods can be quickly The amplitude coefficient of secondary lobe obscuring component Adaptive Suppression, and under operand, it is easy to engineering construction.

The present invention is directed to orientation doppler ambiguity and simultaneously effective inhibit the problem that secondary lobe is fuzzy, it is proposed that Yi Zhongji Doppler ambiguity component Adaptive Suppression method in antenna radiation pattern auxiliary.Literary composition proposes and estimates main lobe initially with NSIE The DoA value of each obscuring component, then derives the DoA information carrying outer secondary lobe obscuring component, and then based on each obscuring component DoA The amplitude coefficient design adaptive spatial filtering device of information and main lobe and secondary lobe obscuring component, extracts each main lobe mould the most successively Stick with paste component and reconstruct without ambiguous Doppler frequency spectrum.Simulation result shows, determines secondary lobe obscuring component amplitude according to antenna radiation pattern Peak sidelobe ratio performance after its imaging of coefficient is compared than not carrying out the suppression of secondary lobe obscuring component, improves about about 9.6dB.This Literary grace parallel processing manner, therefore computational complexity is low, it is easy to engineering construction.

It is understood that unless otherwise defined, all terms used herein (include skill to those skilled in the art of the present technique Art term and scientific terminology) have with the those of ordinary skill in art of the present invention be commonly understood by identical meaning.Also It should be understood that those terms defined in such as general dictionary should be understood that have with in the context of prior art The consistent meaning of meaning, and unless defined as here, will not explain by idealization or the most formal implication.

Above-described detailed description of the invention, has been carried out the purpose of the present invention, technical scheme and beneficial effect further Describe in detail, be it should be understood that the detailed description of the invention that the foregoing is only the present invention, be not limited to this Bright, all within the spirit and principles in the present invention, any modification, equivalent substitution and improvement etc. done, should be included in the present invention Protection domain within.

Claims (1)

1. doppler ambiguity component Adaptive Suppression method based on antenna radiation pattern auxiliary, it is characterised in that include walking as follows Rapid:

Step 1), reception channel signal N number of to airborne synthetic aperture radar carries out distance to pulse compression respectively, and according to following Formula travel direction dimension fast Fourier transform, it is thus achieved that the distance-Doppler numeric field data of each reception passage:

S_n(τ, f)=FFT_t[S_n(τ,t)]

Wherein t be orientation to the time, τ is that distance is to time, S_n(τ, t) is the n-th channel distance signal after pulse compression, FFT_tRepresent that f represents that orientation is to Doppler frequency domain, S about orientation Fourier transformation on time t_n(τ f) is the n-th passage Distance-Doppler numeric field data；

Step 2), for each distance unit, for each doppler cells that this distance unit is corresponding, count as follows Calculate:

Step 2.1), use NSIE technology to estimate the DoA value of each main lobe obscuring componentWhereinRepresent The DoA value of main lobe kth time obscuring component, K is the obscuring component number of main lobe, k=1 ..., K, the most each time main lobe obscuring component is corresponding Spatial domain steering vector be E=[e₁,...,e_k,...,e_K], wherein, e_kFor kth time main lobe obscuring component spatial domain steering vector,D is array element distance, and λ is signal wavelength, and N represents reception port number, subscript^TRepresent Transposition operator；

Step 2.2), calculate each carrier aircraft corresponding to main lobe obscuring component with the relational expression of Space Angle according to following Doppler frequency Real-time speed

${\hat{V}}_k=\frac{\mathrm{\λ}}{2sin\left({\widehat{\mathrm{\β}}}_k\right)}{f}_q,k=1,...,K$

Wherein, f_qFor the Doppler frequency value that this doppler cells is corresponding, q represents that this doppler cells is that this distance unit is corresponding Doppler cells set in q-th doppler cells；

Step 2.3), to step 2.2) in carrier aircraft real-time speed corresponding to each main lobe obscuring component of obtaining be averaged meter Calculate, the carrier aircraft real-time speed estimated value obtained

$\hat{V}=\frac{{\hat{V}}_1+{\hat{V}}_2+...+{\hat{V}}_K}{K}$

Step 2.4), the DoA information of each secondary lobe obscuring component, the i.e. sine value of its corresponding Space Angle is calculated according to equation below

$sin\left({\widehat{\mathrm{\θ}}}_m\right)=\frac{\mathrm{\λ}}{2\hat{V}}{f}_{SL,m}$

Wherein, f_SL,mIt is the Doppler frequency that the m time secondary lobe obscuring component is corresponding,Due to main lobe All there is a secondary lobe component both sides, m=± 1 ..., ± M, M are the natural number more than zero, and PRF is pulse recurrence frequency；

Step 2.5), according to the steering vector that the DoA information each secondary lobe obscuring component of calculating of each secondary lobe obscuring component is corresponding:

A=[a_-M,...,a_m,...,a_M]

Wherein, a_mIt is the m time secondary lobe obscuring component spatial domain steering vector,M=± 1,…,±M；

Step 2.6), build each the spatial domain covariance solving Doppler ambiguity-resolution corresponding to main lobe obscuring component according to below equation Matrix is:

And h ≠ k, m ≠ 0

σ in formula₀For the noise power-value loaded, I ∈ C^N×NUnit matrix, e_hIt it is the spatial domain that the h time main lobe obscuring component is corresponding Steering vector, subscript^HRepresent conjugate transpose operator, a_mFor the m time obscuring component spatial domain steering vector of secondary lobe, ρ_mIt is the m time pair The Amplitude Ration coefficient that lobe obscuring component is corresponding, is represented by:

${\mathrm{\ρ}}_m=\frac{b_m}{F},m=\±1,...,\±M$

Wherein b_mFor the antenna radiation pattern secondary lobe gain that m-th secondary lobe obscuring component is corresponding, F represents that the main lobe of antenna radiation pattern increases Benefit；

Step 2.7), extract the Adaptive beamformer weights W of each main lobe doppler ambiguity component_kFor:

$W_k=\frac{{\stackrel{\‾}{R}}^{-1}{e}_k}{B_k^H{\stackrel{\‾}{R}}^{-1}{B}_k}$

Step 2.8), utilize Adaptive beamformer weights W_kExtract each main lobe obscuring component p_{q_k}For:

$p_{q\_k}=W_k^{H}Z$

Wherein Z=[S₁(i,q),...,S_N(i,q)]^TRepresenting the vector expression of this doppler cells signal, i represents that how general this is Strangling distance unit corresponding to unit is i-th distance unit；

Step 2.9), extract each main lobe obscuring component signal and be designated as P (i, k)=[p_{1_k},...,p_{Na_k}], wherein p_{q_k}It is q The kth main lobe obscuring component that individual doppler cells extracts, Na represents doppler cells number；

Step 3), for each distance unit, according to the different Doppler frequencies that each main lobe obscuring component is corresponding, will be all Main lobe obscuring component signal sequence arranges, and obtains data S (i, f after each distance unit Doppler ambiguity-resolution_a):

S(i,f_aP)=[(i, 1) ..., P (i, K)]

Wherein, f_aRepresent that the orientation after Doppler ambiguity-resolution is to Doppler frequency；

Step 4), obtain the distance-Doppler numeric field data after Doppler ambiguity-resolution, and it is carried out orientation synthetic aperture imaging, Obtain the High Resolution SAR Images after Doppler ambiguity-resolution.