CN101762816A - Joint treatment method and system of static scene and moving object based on satellite-borne MIMO-SAR - Google Patents

Abstract

The invention provides a joint treatment method and a system of a static scene and a moving object based on satellite-borne MIMO-SAR, which relates to the technical field of radars. The method comprises the following steps of: receiving echo data, and carrying out signal sorting on the echo of each receiving array element by utilizing the orthogonality of a transmit signal; eliminating the influence of the phase error in an echo signal on azimuth imaging by equivalent phase center error compensation; carrying out data combination and reconstruction on each equivalent phase center error compensated channel signal to obtain multichannel echo data; realizing the high-resolution wide-swath imaging of a static scene by utilizing one of reconstructed multichannel data, and meanwhile, realizing the detection and the imaging on a moving object in a wide swath by utilizing the joint treatment of each channel data. The invention can improve and broaden the range and the quality of satellite-borne synthetic-aperture radar reconnaissance and monitoring by the wide swath and high resolution and can effectively and simultaneously detect and trace the key moving object in the wide swath, thereby providing the guarantee of comprehensively and timely mastering radar detection information.

Description

A kind of based on satellite-borne MIMO-SAR static scene and moving target combination treatment method and system

Technical field

The present invention relates to the Radar Technology field, more specifically, the present invention relates to combination treatment method and system based on static scene imaging and the moving object detection and the imaging of spaceborne multiple-input and multiple-output synthetic-aperture radar (MIMO-SAR).

Background technology

Satellite-borne synthetic aperture radar (synthetic aperture radar, SAR) as a kind of round-the-clock, round-the-clock, on a large scale, high-resolution sensor, obtained widely using at remote sensing, early warning, scouting, warning numerous areas.

Yet in traditional single channel satellite-borne SAR, azimuthal resolution and two indexs of mapping bandwidth are conflicting, mutual restriction.For this reason, existing solution adopts leggy center SAR (Multiple PhaseCenters SAR usually, MPC-SAR), utilize an emission array element and a plurality of reception array element, replace time-sampling to reduce the requirement of system's pulse repetition rate (PRF) with a plurality of spatial samplings.Yet MPC-SAR adopts single transmitting, and available spatial sampling number is subject to the number that receives array element.Consider the restriction of aspects such as actual spaceborne motion platform size, useful load, reception array element number and the array sizes of MPC-SAR can not roll up.Therefore, MPC-SAR limited in one's ability aspect solution party's bit resolution and mapping bandwidth contradiction.

In addition, as the common problem of motion platform radar, the single channel satellite-borne SAR realizes that there are two large problems in moving object detection and imaging.The first, look the detection of a target under the Texas tower, land clutter distributes extensively, intensity is big, makes faint moving target echo be flooded fully by land clutter; The second, SAR platform motion meeting causes ground, the serious broadening of sea clutter Doppler frequency spectrum, thereby makes traditional doppler filtering method be difficult to realize effective detection of ground microinching target.Expand the hyperchannel satellite-borne SAR of dimension based on the space, can significantly improve clutter and suppress ability, but because it needs hyperchannel physically, the data recording mode of each passage is the same with single-channel SAR in essence, system needs high PRF to avoid the orientation doppler ambiguity, therefore moving target shows not to be to finish in wide swath, and its monitor area is limited in scope.

Mostly existing Spaceborne SAR System is to design at the static scene imaging of high-resolution wide swath or moving object detection and a certain independent function of imaging.For possessing two kinds of functions, often adopt mode of operation switching and time-sharing work (changing the PRF of system) to finish, can not grasp radar detection information comprehensively, timely, be difficult to satisfy modern military and civilian demand.

Summary of the invention

For overcoming existing single channel satellite-borne SAR azimuthal resolution and the conflicting defective of mapping bandwidth, overcome the limited defective of physics of hyperchannel satellite-borne SAR simultaneously, realize wide swath static scene imaging or moving object detection and imaging synchronously, the invention provides combination treatment method and system based on static scene imaging and the moving object detection and the imaging of spaceborne multiple-input and multiple-output synthetic-aperture radar (MIMO-SAR).

According to an aspect of the present invention, provide a kind of, comprising based on the static scene imaging of spaceborne multiple-input and multiple-output synthetic-aperture radar (MIMO-SAR) and the combination treatment method of motive target imaging:

Step 10), according to limited the transmitting-receiving array element of MIMO-SAR, dispose uniform equivalent virtual array;

Step 20), elect the echo data branch of described array received as a plurality of sub-channel signal, and compensate the sub-channel signal of sorting by the equivalent phase errors of centration according to the orthogonality that transmits;

Step 30), each sub-channel signal after the compensation is stored reconstruction multi-channel back wave data along slow time sequencing;

Step 40), obtain the static scene imaging, multi-channel data is united offset processing simultaneously, obtain the imaging of the interior moving target of wide swath according to a certain channel data of the multi-channel data of rebuilding.

Wherein, in the step 10), with M emission array element and N reception array element linear array of MIMO-SAR, p=Nq and M≤N or q=Mp and M 〉=N, wherein, p is the emission array element distance, q is for receiving array element distance.

Wherein, step 20) in, use the difference of equivalent Doppler signal phase place and actual Doppler signal phase place to compensate the echoed signal of sorting.

Wherein, step 30) comprising: according to the array configurations flow pattern, the equivalent array element sample sequential storage during each transmitting-receiving equivalent process to echoed signal makes overlapping equivalent array element appear in adjacent two passages.

Wherein, step 30) in, array PRF satisfies following formula: Wherein, platform motion speed v a, equivalent array element distance d, M is for launching element number of array and N for receiving element number of array.

Wherein, step 40) in, the data in the adjacency channel are made the biasing phase center offset processing, suppress the static target signal, use the phase compensation function to carry out the error signal compensation to the signal after suppressing, obtain the focal imaging of moving target.

According to another aspect of the present invention, provide a kind of, comprising based on the static scene imaging of spaceborne multiple-input and multiple-output synthetic-aperture radar (MIMO-SAR) and the joint processing system of motive target imaging:

The antenna receiving-sending subsystem is used for disposing uniform equivalent virtual array according to limited the transmitting-receiving array element of MIMO-SAR;

The signal sorting module is used for electing the echo data branch of described array received as a plurality of sub-channel signal according to the orthogonality that transmits;

Phase compensation block is used for compensating by the equivalent phase errors of centration sub-channel signal of sorting;

The data combination module is used for each sub-channel signal after the compensation is stored along slow time sequencing, rebuilds the multi-channel back wave data;

High resolving power wide swath static scene image-forming module and moving object detection and image-forming module, be used for obtaining the static scene imaging according to a certain channel data of the multi-channel data of rebuilding, simultaneously multi-channel data is united and offset processing, obtain the imaging of moving target in the wide swath.

Wherein, in the described antenna receiving-sending subsystem, with M emission array element and N reception array element linear array of MIMO-SAR, p=Nq and M≤N or q=Mp and M 〉=N, wherein, p is the emission array element distance, q is for receiving array element distance; Described phase compensation block uses the difference of equivalent Doppler signal phase place and actual Doppler signal phase place to compensate the echoed signal of sorting.

Wherein, described data combination module is according to the array configurations flow pattern, and the equivalent array element sample sequential storage during each transmitting-receiving equivalent process to echoed signal makes overlapping equivalent array element appear in adjacent two passages; Wherein, array PRF need satisfy following formula:

Wherein, platform motion speed v _a, equivalent array element distance d, M is for launching element number of array and N for receiving element number of array.

Wherein, described high resolving power wide swath static scene image-forming module and moving object detection and image-forming module are made the biasing phase center to the data in the adjacency channel and are offseted processing, suppress the static target signal, use the phase compensation function to carry out the error signal compensation to the signal after suppressing, obtain the focal imaging of moving target.

By using the present invention, can not only improve and widen the scope and the quality of satellite-borne synthetic aperture radar scouting and supervision by wide swath and high resolving power, and can carry out effective detection, the tracking of emphasis moving target in the wide swath simultaneously, provide assurance for grasping radar detection information comprehensively, timely.

Description of drawings

Fig. 1 is static scene model according to an embodiment of the invention;

Fig. 2 is the combination treatment method process flow diagram of MIMO-SAR quiescent imaging and moving target;

Fig. 3 is MIMO-SA array configurations and MPC-SAR array configurations synoptic diagram;

Fig. 4 is the signal sorting synoptic diagram;

Fig. 5 is an equivalent phase center processing synoptic diagram;

Fig. 6 rebuilds synoptic diagram for the binary channels data combination;

Fig. 7 is a high resolving power wide swath static scene imaging process flow diagram;

Fig. 8 is a based on satellite-borne MIMO-SAR static scene imaging synoptic diagram;

Fig. 9 is a single channel satellite-borne SAR static scene imaging synoptic diagram;

Figure 10 is moving object detection and focal imaging process flow diagram;

Figure 11 is that passage 1 equivalent array element and moving target space geometry concern synoptic diagram;

Figure 12 handles prepass 1 image synoptic diagram for DPCA;

Figure 13 handles the back result schematic diagram for DPCA;

Figure 14 is the orientation imaging results of the preceding moving target of error signal compensation;

Figure 15 is the orientation focal imaging result of error signal compensation back moving target.

Embodiment

Below in conjunction with the drawings and specific embodiments, a kind ofly be described in detail based on the quiescent imaging of spaceborne multiple-input and multiple-output synthetic-aperture radar (MIMO-SAR) and the combination treatment method and the system of moving object detection and imaging to provided by the invention.

Multiple-input and multiple-output synthetic-aperture radar (MIMO-SAR) is the nearly 2 years a kind of New System radars that put forward.In September, 2007, the breadboard J.H.G.Ender of Germany FANG provides the definition of MIMO-SAR first in international radar meeting, think " if the coherent MIMO radar of a motion utilizes the coherent accumulation of echoed signal between arteries and veins to be used for the imaging purpose; then it is defined as MIMO-SAR " (J.H.G.Ender, MIMO-SAR.International radar conference, IRS07, Cologne, Sept, 2007.).

Fig. 1 illustrates static scene model according to an embodiment of the invention.In the present embodiment, Fig. 1 provides six static targets, as the object of present embodiment static scene processing.In this based on satellite-borne MIMO-SAR system, the radar operation wavelength is λ=0.03m; Platform speed is v _a=7200m/s; Mapping band center oblique distance R _c=800km; Emission array element number M=2, its array element distance p=12m; Receive array element number N=3, its array element distance q=4m; Receive/send out the array element orientation and be all D=4m to size; Radar pulse repetition frequency PRF=1200Hz; Emission is with the time domain orthogonal signal of frequency band; The equivalent sampling sample makes up the binary channels data when utilizing sky.Certainly, one of ordinary skill in the art will appreciate that the object of handling as static scene can be not limited to the position of above-mentioned six static targets, can select other position arbitrarily for use.And other parameters of system only are used to illustrate embodiments of the invention, rather than limit the invention.

Fig. 2 is the combination treatment method process flow diagram of MIMO-SAR quiescent imaging and moving target according to an embodiment of the invention.As shown in Figure 2, the method for present embodiment comprises: configuration is as the radar array of physical support, by realizing uniform equivalent virtual array, the echoed signal of receiving radar target; The echoed signal sorting utilizes the orthogonality that transmits and collect, and exports the corresponding echo that respectively transmitted; The echo of thinking that equivalent array element internal loopback obtains is obtained in the compensation of equivalent phase errors of centration; The multi-channel data combination is carried out data recombination to each the subchannel echo after the phase compensation, obtains the required multi-channel data of subsequent treatment; The imaging of high-resolution wide swath static scene, and in wide swath, finish moving object detection and imaging simultaneously.Below describe the specific implementation of each step in detail.

The array configurations scheme

The transmitting-receiving array is to transmit and receive the physical support of echo, and its array configurations exists diversity and complicacy, and different system optimization targets can obtain different array configurations.In the present embodiment, utilize a limited number of emission/reception array element, obtain uniform equivalent virtual array, and the non-overlapped number of equivalent array element is maximum, i.e. the spatial degrees of freedom maximum.Reduce the signal Processing complexity by uniform sampling, and guarantee SAR orientation image quality, spatial degrees of freedom can improve the signal Processing performance greatly simultaneously.

In one embodiment, a kind of array configurations of MIMO-SAR is provided, with M emission array element and N reception array element linear array, wherein, the emission array element distance is p, and the reception array element distance is q, for making the array total length short as far as possible, need side's dense arrangement that array number is many during configuration, few sparse arrangement of a side, and both array element distance are done a constraint.For example, when launching array number M greater than reception array number N, desirable q=Mp, opposite desirable p=Nq.Allocation plan specifically can be expressed as: p=Nq, M≤N or q=Mp, M 〉=N.Here, first can be launched array element and first reception array element, utilize the T/R assembly to realize the switching that transmits and receives with putting, so available M+N-1 transmitting-receiving array element in the practical application, once the transmitting-receiving processing forms MN non-overlapped equivalent spatial sampling.Certainly, also can all adopt transmitting-receiving array element to obtain equivalent spatial sampling, but can form overlapping spatial sampling with the mode of putting (switching of T/R assembly).

Fig. 3 has specifically provided the synoptic diagram of MIMO-SAR and the contrast of MPC-SAR array configurations.Can see, distribute rationally can make MIMO-SAR once receive and dispatch in non-overlapped equivalent virtual element number of array reach MN.Under the condition that equivalent element position is identical in once receiving and dispatching, array element sum and the aperture total length of MIMO-SAR significantly reduce than MPC-SAR system simultaneously.Therefore, compare with existing MPC-SAR, when equivalent array number was identical, MIMO-SAR can significantly reduce the requirement to actual array element number and array sizes, thereby can alleviate the pressure of the limited motion platform of useful load.

The echoed signal sorting

Each receives array element and receives after the echo because M emission array element sends time domain orthogonal waveform with frequency range simultaneously, so each echo that receives array element be the linearity of M the corresponding echo that transmits add with.The effect of signal sorting is exactly an orthogonality of utilizing the collection that transmits, and corresponding echo is respectively transmitted.Fig. 4 is the inside implementation structure of signal sorting, and each receives array element and connects M sub-receiving cable, and its corresponding respectively adaptation function that respectively transmits is according to transmitting and adaptation function mates sorting with echoed signal.

The compensation of equivalent phase errors of centration

Then, for the separation results of echoed signal, the phase error that compensation equivalent phase center processing is introduced is obtained the echo that can think that equivalent array element internal loopback obtains.

Appoint and get m emission array element and n reception array element, its equivalent phase center processing synoptic diagram as shown in Figure 5.At slow time t constantly, receive the echoed signal that array element n receives self-emission array element m, the phase place of its actual Doppler signal is designated as

Define the position of two array element centre positions for its equivalent phase center.Equivalence Doppler signal phase place can be thought the distance R of equivalent array element P to impact point T _e(t) phase place that round trip time-delay obtains is designated as

Here, with the difference of equivalent Doppler signal phase place and actual Doppler signal phase place Be called the equivalent phase errors of centration, the compensation of being done at the equivalent phase errors of centration is called the compensation of equivalent phase errors of centration.

With oblique distance R _m(t), R _n(t) and R _e(t) be Taylor and launch, can put in order and obtain

Wherein, the relative distance that Δ x represents to launch array element 0 and receives array element 0, n=0,1 ..., N-1, m=0,1,, M-1 represents to receive array element and emission array element sequence number respectively, and p, q represent to launch array element distance respectively and receive array element distance, M wherein, N is respectively the number that transmits and receives array element, and λ is the radar operation wavelength, R _cBe the vertical oblique distance of Texas tower to the imaging scene center.

Obvious by formula (3), the equivalent phase errors of centration is irrelevant with the slow time, therefore can easily carry out the effectively compensating of MIMO-SAR system.

The multi-channel data combination

After the compensation of equivalent phase errors of centration, each the subchannel echo after the phase compensation is carried out data recombination, obtain the required multi-channel data of subsequent treatment.For realizing two kinds of functions of static scene imaging of high-resolution wide swath and moving object detection and imaging simultaneously, make up the binary channels data, Fig. 6 has specifically provided the data combination synoptic diagram.T wherein, t-1/PRF, t+1/PRF represent adjacent three corresponding slow times of transmitting-receiving, and PRF is the pulse repetition rate of system.Equivalence array element is placed along the slow time successively, is the position relation of equivalent array element during outstanding each adjacent transmitting-receiving is handled, and there is crossover in the demonstration of among Fig. 6 equivalent array element being staggered with demonstration.The data at equivalence array element place are equivalent spatial sampling sample, available signal collection { x _IrExpression, and the corresponding slow time t of i sequence number constantly wherein, r=0,2 ..., MN-1 represents the sequence number of equivalent array element in each time transmitting-receiving.MN=6 in this example, therefore during each transmitting-receiving equivalent process, first three equivalent spatial sampling sample can be combined in the passage 1, three the equivalent spatial sampling samples in back are combined in the passage 2, along the order of slow time equivalent sample order are stored the required binary channels data that obtain just capable of being combined like this.The binary channels data can use respectively set of signals ..., x _{(i-1) 0}, x _{(i-1) 1}, x ( _{I-1) 2}, x _I0, x _I1, x _I2... with ..., x _{(i-1) 3}, x _{(i-1) 4}, x _{(i-1) 5}, x _I3, x _I4, x _I5... represent.

For those skilled in the art, be appreciated that if want to make up the data of ζ passage, the equivalent spatial sampling number of samples Δ n=MN/ ζ of each channel allocation during then once transmitting-receiving is handled, Δ n is an integer, as ζ=2 being arranged in the present embodiment, Δ n=3.For guarantee that each channel data samples evenly in the whole slow time, overlapping equivalent array element appears in adjacent two passages, requires the platform motion speed v _a, equivalent array element distance d and array PRF satisfy following relational expression

$\mathrm{PRF}=\frac{\mathrm{\ζ}\·v_a}{\mathrm{MN}\·d}---\left(4\right)$

In the present embodiment, at first, because spatial sampling replaces time-sampling, the contradiction of wide swath and high azimuthal resolution when utilizing each channel data can solve the static scene imaging; If the equivalent array element distance of single-channel SAR is similarly d, then the pulse repetition rate PRR of its work _s=v _a/ d has relational expression with formula (4) contrast As PRF=PRF in the present embodiment _s/ 3.Low pulse repetition rate can guarantee that the wide swath scene distance is fuzzy, and spatial sampling replaces the time-sampling technology can the equivalent raising PRF of system, guarantees that with this Doppler is fuzzy.Second, utilize the space-time joint processing of a plurality of channel datas can realize that moving-target detects and imaging function, as shown in Figure 6,2 three equivalent element positions of 1 three equivalent element positions of passage and slow time t-1/PRF moment passage are identical constantly for slow time t, for ground arbitrary static target, two passages have identical equivalent spatial sampling information, and moving target can be variant two slow sample information constantly, therefore utilize a plurality of interchannel Combined Treatment can effectively suppress static clutter, improve moving-target and detect performance.

Utilize data combination provided by the invention, can realize two kinds of described data of function of static scene imaging of high-resolution wide swath and moving object detection and imaging simultaneously.Present embodiment also may be used in the MPC-SAR radar that single-shot overcharges, but the ability to work of MPC-SAR is not as good as MIMO-SAR.

The imaging of high resolving power wide swath static scene

The data of a certain passage after the reception data combination are obtained high-resolution wide swath imaging results.The specific implementation algorithm is identical with traditional SAR imaging process, can adopt RD, CS or RMA scheduling algorithm.With the RD imaging algorithm is example, and Fig. 7 has provided the basic procedure of static scene imaging, at first the channel data of rebuilding is carried out range migration correction, constructs the direction reference function then and realizes the orientation compression, and then obtain final static scene imaging results.

Fig. 8 has provided the imaging results of based on satellite-borne MIMO-SAR static scene.Contrast as can be known with the single channel satellite-borne SAR of Fig. 9, both imaging effects are basic identical, but the former pulse repetition rate size is 1/3 of a single channel satellite-borne SAR, so the based on satellite-borne MIMO-SAR system can satisfy the requirement of wide swath imaging guaranteeing the high-resolution while of orientation.

Moving object detection and imaging

Receive the multi-channel data that combination obtains, realize the focal imaging of moving target.In the present embodiment, at first, moving object detection and imaging and two functions of high-resolution wide swath static scene imaging can realize simultaneously; Secondly, moving object detection is finished with being imaged in the wide swath, has widened scouting and investigative range.

Figure 10 has provided the process flow diagram that utilizes the binary channels data to realize moving object detection and focal imaging in detail.Be appreciated that channel data used in the present invention is not limited to binary channels, can select a plurality of channel datas.In the present embodiment, because the binary channels data utilize equivalent spatial sampling to combine, therefore during MIMO-SAR once receives and dispatches equivalent process, moving target will be in " stationary state ", and this point and traditional Dual-Channel SAR are different.For image illustrates this singularity, Figure 11 has provided that equivalent array element and moving target space geometry concern synoptic diagram in the passage 1, wherein n _sAnd n _mRepresent equivalent array element and moving target respectively with the call number of slow time, both satisfy relational expression n _m=n _s-mod (n _s, Δ n), ' mod ' expression mould Value Operations, Δ n=3 in this example.When equivalent array element sequence number is followed successively by n _s=... ,-3 ,-2 ,-1,0,1,2,3,4,5 ... the time, then the index sequence number of moving target is followed successively by n _m=... ,-3 ,-3 ,-3,0,0,0,3,3,3 ..., n _sWith n _mThe difference of call number has reflected that then spatial sampling replaces time-sampling to handle the singularity of the moving target that is brought.Particularly, the binary channels doppler echo of moving target place range unit can be expressed as

$x_i\left(n_s\right)=\mathrm{\&sigma;}\&CenterDot;\mathrm{rect}\left(\frac{n_s}{N_s}\right)\exp \{-\mathrm{<figure-callout\; id="4"\; label="j"\; filenames="H2008102405789E0000041.png"\; state="\{\{state\}\}">j</figure-callout>}\frac{4\mathrm{\&pi;}}{\mathrm{\&lambda;}}{R}_i\left(n_{s}T\right)\},i=\mathrm{1,2}---\left(5\right);$

Wherein, i represents passage call number, N _s=T _sPRF _eBe synthetic aperture T in the time _sInterior sampling number, T=1/PRF _eBe equivalent pulse recurrence interval, PRF _e=Δ nPRF represents equivalent pulse repetition frequency, R _i(n _sT), i=1,2, represent slow time t=n respectively _sIn the T moment, the equivalent array element of passage 1,2 correspondence and the distance of moving target can be designated as

$R_i\left(n_{s}T\right)\&ap;R_c+v_r{n}_{s}T+\frac{{(v_a(n_s+(i-1)\mathrm{\&Delta;n})T-v_x{n}_{s}T)}^2}{2R_c}-v_r{n}^{\&prime;}T---\left(6\right);$

Wherein, n '=mod (n _s, Δ n), v _rAnd v _xRepresent that respectively the radial velocity of moving target and orientation are to speed.

According to the treatment scheme of Figure 10, earlier with passage 2 data x ₂The Δ n that moves to right on time, and with passage 1 data x ₁Offset processing, this step also can be described as biasing phase center (DPCA) and offsets processing.Result is expressed as

$x\left(n_s\right)\&ap;x_e\left(n_s\right)x_c\left(n_s\right)(1-\exp \left(\mathrm{<figure-callout\; id="4"\; label="j"\; filenames="H2008102405789E0000041.png"\; state="\{\{state\}\}">j</figure-callout>}\frac{4\mathrm{\&pi;}}{\mathrm{\&lambda;}}{v}_r\mathrm{\&Delta;nT}\right))---\left(7\right);$

In the expression formula (3), x _e(n _s) doppler echo of corresponding traditional single-channel SAR, and x _c(n _s) then be the reflection of singularity in echo model of moving target during the space equivalent sampling is handled, be referred to as error signal.Work as v _r=0 o'clock, x (n _s)=0 shows that static target can be inhibited, and moving-target is owing to have movable information and can exist and offset residue, thereby can realize effective detection of moving target.x _e(n _s) and x _c(n _s) expression formula can be designated as respectively

$x_e\left(n_s\right)=\mathrm{\&sigma;}\&CenterDot;\mathrm{rect}\left(\frac{n_s}{N_s}\right)\exp (\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="H2008102405789E0000041.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;}{f}_{D}T{n}_s+\mathrm{j\&pi;}{k}_m{T}^2{n}_s^2)---\left(8\right);$

$x_c\left(n_s\right)=g\left(n_s\right)\&CenterDot;(x_c^{\&prime;}\left(n_s\right)\&CircleTimes;\underset{r=-\&infin;}{\overset{+\&infin;}{\mathrm{\&Sigma;}}}\mathrm{\&delta;}(n_s-\mathrm{r\&Delta;n}))---\left(9\right);$

F wherein _D=-2v _r/ λ and k _m=-2 (v _a-v _x) ²/ (λ R _c) representing the doppler centroid and the chirp rate of moving target respectively, σ is the moving target backscattering coefficient. The expression rectangular function, δ () represents impulse function, Be convolution operation.Formula (9) shows that the error signal in the new model is the sequence of blocking of periodic sequence, and x ' _c(n _s) then specifically represent the sequential value in the one-period, be designated as

$x_c^{\&prime;}\left(n_s\right)=\exp \left(\mathrm{<figure-callout\; id="4"\; label="j"\; filenames="H2008102405789E0000041.png"\; state="\{\{state\}\}">j</figure-callout>}\frac{4\mathrm{\&pi;}{v}_r{n}_{s}T}{\mathrm{\&lambda;}}\right),n_s=\mathrm{0,1},...,\mathrm{\&Delta;n}-1---\left(10\right);$

Offset and obtain x (n _s) after, follow-up processing flow is the orientation compression process among Figure 10.Because the orientation of moving target to speed and radial velocity the unknown, therefore needs to estimate the Doppler parameter of moving-target, i.e. doppler centroid and chirp rate, thus structure and then is realized the focal imaging of moving-target at the direction reference function of moving target.But, moving target focal imaging flow process and traditional SAR have difference among the present invention, increase the error signal compensation.This is because have error signal x in the new signal model _c(n _s) modulation (seeing formula (7)) because this error signal has periodically,, then can cause the appearance of " ghost peak " in the orientation compression result if not to its compensation.The corresponding error signal x of the phase compensation function of being constructed among Figure 10 _c(n _s) conjugation, its objective is the influence of eliminating error signal.Below " ghost peak " and error signal compensation problem are provided concrete analysis.

According to the treatment scheme of Figure 10, if the uncompensation error signal, and get the static target reference function

Wherein

Expression static target chirp rate, then the orientation compression result is x _Ref(n _s) and x (n _s) convolution.Ignore constant term, then the orientation compression result is

$\left|y\left(n^{\&prime;}\right)\right|=|\underset{n_s=-\frac{N_m}{2}}{\overset{\frac{N_m}{2}-1}{\mathrm{\&Sigma;}}}\mathrm{rect}\left(\frac{n_s}{N_m}\right)\mathrm{rect}\left(\frac{n^{\&prime;}-n_s}{N_m}\right)x_c\left(n_s\right)\&CenterDot;x_m\left(n_s\right)\&CenterDot;\exp (-j\left(2\mathrm{\&pi;}\right|k_s\left|T^2{n}^{\&prime;}\right)n_s)|---\left(11\right);$

N ' ∈ (N wherein _m, N _m).N _m=T _mPRF _eT aperture time is handled in expression _mInterior sampling number, and

Expression moving target residue signal.Formula (7) further can be expressed as

$\left|y\left(n^{\&prime;}\right)\right|=\left\{\begin{array}{c}|X_{\mathrm{cm}}\left(\mathrm{\&omega;}\right)-X_{\mathrm{can}}^{\left(R\right)}\left(\mathrm{\&omega;}\right)|,0\&le;n^{\&prime;}\&le;N_s-1\\ |X_{\mathrm{cm}}\left(\mathrm{\&omega;}\right)-X_{\mathrm{can}}^{\left(L\right)}\left(\mathrm{\&omega;}\right)|,-N_s+1\&le;n^{\&prime;}<0\end{array}\right.---\left(12\right);$

Formula (12) illustrates the available X of orientation compression result y (n ') _Cm(ω), X _Can ^(R)(ω) and X _Can ^(L)(ω) three parts are described, wherein X _Cm(ω) be the x of sequence _c(n _s) x _m(n _s) Fourier transform, and X _Can ^(L)(ω) and X _Can ^(R)(ω) then can play and offset X _CmThe effect of redundancy (ω), the final synthetic y (n ') that obtains.The formula that embodies of three parts is:

$\left\{\begin{array}{c}{X}_{\mathrm{cm}}\left(\mathrm{\&omega;}\right)=\underset{n_s=-\frac{N_m}{2}}{\overset{\frac{N_m}{2}-1}{\mathrm{\&Sigma;}}}{x}_c\left(n_s\right)\&CenterDot;x_m\left(n_s\right)\&CenterDot;\exp (-\mathrm{j\&omega;}{n}_s)\left(a\right)\\ X_{\mathrm{can}}^{\left(R\right)}\left(\mathrm{\&omega;}\right)=\underset{n_s=-\frac{N_m}{2}}{\overset{n^{\&prime;}-\frac{N_m}{2}-1}{\mathrm{\&Sigma;}}}{x}_c\left(n_s\right)\&CenterDot;x_m\left(n_s\right)\&CenterDot;\exp (-\mathrm{j\&omega;}{n}_s)\left(b\right)---\left(13\right);\\ X_{\mathrm{can}}^{\left(L\right)}\left(\mathrm{\&omega;}\right)=\underset{n_s=n^{\&prime;}+\frac{N_m}{2}}{\overset{\frac{N_m}{2}-1}{\mathrm{\&Sigma;}}}{x}_c\left(n_s\right)\&CenterDot;x_m\left(n_s\right)\&CenterDot;\exp (-\mathrm{j\&omega;}{n}_s)\left(c\right)\end{array}\right.$

ω in the formula (13)=2 π (n '/N _m) (B _s/ PRF _e), B _sFor handling T aperture time _mInterior static target doppler bandwidth, definition u _s=B _s/ PRF _eBe scale factor.Because n ' ∈ (N _m, N _m), so be ω ∈ (2 π u between the Support of angular frequency _s, 2 π u _s).

Further can be with X _Cm(ω) be expressed as

$X_{\mathrm{cm}}\left(\mathrm{\&omega;}\right)=\frac{1}{2\mathrm{\&pi;}}H\left(\mathrm{\&omega;}\right)\&CircleTimes;X_m\left(\mathrm{\&omega;}\right)---\left(14\right);$

Wherein H (ω) and X _m(ω) the corresponding x of difference _c(n _s) and x _m(n _s) Fourier transform.X _mThe degree that defocuses that has reflected moving-target between Support (ω).And H (ω) is a series of impulse strings that are spaced apart 2 π/Δ n, H in the impulse string (ω), ω ≠ 0 and X _mConvolution results (ω) then is the reason that " ghost peak " produces.At whole matched filtering interval (2 π u _s, 2 π u _s), promptly corresponding (T _m, T _m) in, the number that " ghost peak " occurs is 2floor (u _sΔ n), wherein floor () expression rounds downwards.H (ω) can be expressed as

$H\left(\mathrm{\&omega;}\right)=\frac{2\mathrm{\&pi;}}{\mathrm{\&Delta;n}}\underset{k=-{\mathrm{\&mu;}}_s\&CenterDot;\mathrm{\&Delta;n}}{\overset{{\mathrm{\&mu;}}_s\&CenterDot;\mathrm{\&Delta;n}-1}{\mathrm{\&Sigma;}}}{X}_c^{\&prime;}\left(k\right)\mathrm{\&delta;}(\mathrm{\&omega;}-\frac{2\mathrm{\&pi;}}{\mathrm{\&Delta;n}}k)---\left(15\right);$

$X_c^{\&prime;}\left(k\right)=\exp \left(j(\frac{2\mathrm{\&pi;}}{\mathrm{\&lambda;}}{v}_{r}T-\frac{\mathrm{\&pi;}}{\mathrm{\&Delta;n}}k)(\mathrm{\&Delta;n}-1)\right)\&CenterDot;\frac{\sin (\frac{2\mathrm{\&pi;}}{\mathrm{\&lambda;}}{v}_r\mathrm{T\&Delta;n}-\mathrm{\&pi;k})}{\sin (\frac{2\mathrm{\&pi;}}{\mathrm{\&lambda;}}{v}_{r}T-\frac{\mathrm{\&pi;}}{\mathrm{\&Delta;n}}k)}---\left(16\right);$

Compensating error signal x _c(n _s) can eliminate " ghost peak " influence.Radial velocity restricts although error signal is subjected to moving target, and it is irrelevant with the slow time, therefore makes things convenient for system balance.Because plural phase place is the cycle with 2 π, and radial velocity has corresponding relation with doppler centroid, therefore utilizes the doppler centroid after bluring also can effectively compensate error signal.Yet, consider that error signal can influence doppler spectral and there are " frequency spectrum division " these two factors in doppler spectral self, adopt the stronger self-focusing search plan of robustness among the present invention, its best image quality index (as image entropy, the integration secondary lobe than or false secondary lobe compare etc.) search value of corresponding ideal then.Owing to can detect the range unit at target place after static clutter suppresses, and number is limited, so the operand that the self-focusing search plan increases can be accepted.

In according to another embodiment of the invention, provide a kind of based on spaceborne multiple-input and multiple-output synthetic-aperture radar (MIMO-SAR) quiescent imaging and the system of the Combined Treatment of motive target imaging, described system comprises: the antenna receiving-sending subsystem, be responsible for the emission of the many detectable signals of quadrature and the reception of the interior radar return of observation scene, it is configured the radar array as physical support, by realizing uniform equivalent virtual array, the echoed signal of receiving radar target; Signal processing subsystem is responsible for the analysis and the processing of echoed signal, divides by effect specifically to comprise signal sorting module, phase compensation block, data combination module, high resolving power wide swath static scene image-forming module and moving object detection and image-forming module; Wherein, the orthogonality that the utilization of signal sorting module transmits and collects, export the corresponding echo that respectively transmitted, the compensation of phase compensation block equivalent phase errors of centration, handle the phase error of being introduced, obtain the echo of thinking that equivalent array element internal loopback obtains, the data combination module, each subchannel echo after the phase compensation is carried out data recombination, obtain the required multi-channel data of subsequent treatment, high resolving power wide swath static scene image-forming module and moving object detection and image-forming module are used for the static scene imaging of high-resolution wide swath and moving object detection and imaging, realize moving object detection and imaging and the imaging of high-resolution wide swath static scene simultaneously, and in wide swath, finish moving object detection and imaging; The terminal display subsystem is responsible for the demonstration of signal processing results.In described system, the step in can corresponding said method realizing in the respective modules separately, does not repeat them here.

Supposing has a moving target, its radial velocity v in the static scene shown in Figure 1 _r=5m/s, the orientation is to speed v _x=10m/s, initial position be (0, R _c), Figure 12 is subjected to the influence of static target for the data of DPCA processing prepass 1, and the moving-target data are difficult to be distinguished; Figure 13 is passage 1 and the result of passage 2 data after DPCA handles, and owing to static target is greatly suppressed, so the moving-target data are highlighted fully.Figure 14 is error signal x _c(n _s) the preceding moving target orientation of compensation imaging results.Theoretical analysis is known: if do not carry out the error signal compensation, will have " ghost peak " in the moving-target orientation imaging results, and " ghost peak " number is 2floor (3/1.2)=4; Be subjected to the influence of radial velocity, moving target will depart from initial orientation position pact-v _rR _c/ v _a=-555.5m; In addition, because v _x＜v _aSo moving target defocuses not serious.Obvious, Figure 14 conforms to fully with theoretical analysis.Figure 15 shows that the error signal that the compensation radial velocity is introduced can effectively be eliminated the influence of " ghost peak ".

It should be noted that at last, above embodiment is only in order to illustrate that technical scheme of the present invention is not intended to limit, and on using, can extend to other modification, variation, application and embodiment, think that simultaneously all such modifications, variation, application, embodiment are within the spirit and scope of the present invention.

Claims (10)

1. one kind based on the static scene imaging of spaceborne multiple-input and multiple-output synthetic-aperture radar (MIMO-SAR) and the combination treatment method of motive target imaging, comprising:

Step 10), according to limited the transmitting-receiving array element of MIMO-SAR, dispose uniform equivalent virtual array;

Step 20), elect the echo data branch of described array received as a plurality of sub-channel signal, and compensate the sub-channel signal of sorting by the equivalent phase errors of centration according to the orthogonality that transmits;

Step 30), each sub-channel signal after the compensation is stored reconstruction multi-channel back wave data along slow time sequencing;

Step 40), obtain the static scene imaging, multi-channel data is united offset processing simultaneously, obtain the imaging of the interior moving target of wide swath according to a certain channel data of the multi-channel data of rebuilding.

2. the process of claim 1 wherein, in the step 10), with M emission array element and N reception array element linear array of MIMO-SAR, p=Nq and M≤N or q=Mp and M 〉=N, wherein, p is the emission array element distance, q is for receiving array element distance.

3. the process of claim 1 wherein step 20) in, use the difference of equivalent Doppler signal phase place and actual Doppler signal phase place to compensate the echoed signal of sorting.

4. the process of claim 1 wherein step 30) comprising: according to the array configurations flow pattern, equivalent array element sample uniform sampling and sequential storage during each transmitting-receiving equivalent process to echoed signal make overlapping equivalent array element appear in adjacent two passages.

5. the method for claim 4, wherein, step 30) in, array PRF satisfies following formula:

Wherein, platform motion speed v a, equivalent array element distance d, M is for launching element number of array and N for receiving element number of array.

6. the process of claim 1 wherein step 40) in, data in the adjacency channel are made the biasing phase center offset processing, suppress the static target signal, use the phase compensation function to carry out the error signal compensation, obtain the focal imaging of moving target the signal after suppressing.

7. one kind based on the static scene imaging of spaceborne multiple-input and multiple-output synthetic-aperture radar (MIMO-SAR) and the joint processing system of motive target imaging, comprising:

The antenna receiving-sending subsystem is used for disposing uniform equivalent virtual array according to limited the transmitting-receiving array element of MIMO-SAR;

The signal sorting module is used for electing the echo data branch of described array received as a plurality of sub-channel signal according to the orthogonality that transmits;

Phase compensation block is used for compensating by the equivalent phase errors of centration sub-channel signal of sorting;

The data combination module is used for each sub-channel signal after the compensation is stored along slow time sequencing, rebuilds the multi-channel back wave data;

High resolving power wide swath static scene image-forming module and moving object detection and image-forming module, be used for obtaining the static scene imaging according to a certain channel data of the multi-channel data of rebuilding, simultaneously multi-channel data is united and offset processing, obtain the imaging of moving target in the wide swath.

8. the system of claim 7 wherein, in the described antenna receiving-sending subsystem, receives the array element linear array with M emission array element of MIMO-SAR and N, p=Nq and M≤N or q=Mp, and wherein, p is the emission array element distance, q is the reception array element distance; Described phase compensation block uses the difference of equivalent Doppler signal phase place and actual Doppler signal phase place to compensate the echoed signal of sorting.

9. the system of claim 7, wherein, described data combination module is according to the array configurations flow pattern, and equivalent array element sample uniform sampling and sequential storage during each transmitting-receiving equivalent process to echoed signal make overlapping equivalent array element appear in adjacent two passages; Wherein, array PRF need satisfy following formula:

Wherein, platform motion speed v _a, equivalent array element distance d, M is for launching element number of array and N for receiving element number of array.

10. the system of claim 7, wherein, described high resolving power wide swath static scene image-forming module and moving object detection and image-forming module are made the biasing phase center to the data in the adjacency channel and are offseted processing, suppress the static target signal, use the phase compensation function to carry out the error signal compensation to the signal after suppressing, obtain the focal imaging of moving target.

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