CN104678393A - Subaperture wave number domain imaging method for squint sliding spotlight SAR (Synthetic Aperture Radar) - Google Patents

Abstract

The invention discloses a subaperture wave number domain imaging method for a squint sliding spotlight SAR (Synthetic Aperture Radar). A traditional sliding spotlight SAR subaperture method is improved aiming at squint conditions. The subaperture wave number domain imaging method comprises the following steps: firstly, overlapping a whole aperture and dividing subapertures; taking an extended wave number domain method used for the squint conditions as a subaperture basic imaging method; and finishing azimuth processing in a distance Doppler domain by adopting an improved BAS method to splice the subapertures, so as to obtain a whole aperture image under the squint conditions. With the adoption of the subaperture wave number domain imaging method, the problems of the squint sliding spotlight SAR of large data size, non-zero azimuth Doppler center and oversized Doppler bandwidth are solved, and the practical value is larger.

Description

The sub-aperture wavenumber domain formation method of stravismus Sliding spotlight SAR

Technical field

The present invention relates to radar imaging technology field, particularly relate to a kind of sub-aperture wavenumber domain formation method looking side ways Sliding spotlight SAR.

Background technology

Synthetic-aperture radar is one high-resolution imaging radar all-time anf all-weather, all plays significant role in dual-use field.Slip beam bunching mode is a kind of new synthetic-aperture radar (Synthetic Aperture Radar, SAR) imaging pattern, it carrys out control azimuth resolution by control antenna irradiated site in the translational speed on ground, obtain the imaging area larger than beam bunching mode, higher than same antenna size band pattern azimuthal resolution.Therefore, slip beam bunching mode all has a wide range of applications at airborne and satellite-borne SAR.

Under slip beam bunching mode, the synthetic aperture time of target is long, and the Doppler frequency center of echo changes along with the position of orientation of target, causes its doppler bandwidth to strain mutually greatly.In order to avoid aliasing appears in azimuth spectrum, pulse repetition rate (Pulse repetition frequency, PRF) must be met and be greater than doppler bandwidth.

Orientation spectral aliasing can be solved by the method dividing sub-aperture.Sub-aperture shot is that full aperture overlap is divided into N (N >=2) individual sub-aperture, to the process of each sub-aperture Dynamic data exchange, finally resolution image is helped in data splicing.Sub-aperture process not only can solve orientation spectral aliasing, and lower to request memory, when echo data amount is larger, has good dirigibility.But the sub-aperture shot being applicable to positive side-looking situation can not be completely applicable for stravismus situation.

Summary of the invention

Technical matters to be solved by this invention is the defect for background technology, provides a kind of sub-aperture wavenumber domain formation method looking side ways Sliding spotlight SAR.

The present invention is for solving the problems of the technologies described above by the following technical solutions:

The sub-aperture wavenumber domain formation method of stravismus Sliding spotlight SAR, comprises the steps:

Step 1), by N _a× N _rfull aperture radar return data overlap be divided into several sub-aperture, each sub-aperture echo data is N _ai× N _r, and according to dividing the size determination sub-aperture number of lap between the size of sub-aperture and any two sub-aperture: the value rounded off to negative direction adds 1;

Wherein, N _afor full aperture radar echo pulse number, N _rfor distance is to sampling number, N _aifor each sub-aperture echo-pulse number, i is the index of sub-aperture, and Δ N is the size of lap between described two sub-aperture;

Step 2), expansion space virtual detection techniques is used respectively to the sub-aperture divided: first orientation is carried out to FFT to the sub-aperture echo data after pulse pressure, then carry out consistent compression and Stolt interpolation in two-dimensional frequency, last length obtains basic imaging results as IFFT;

Step 3), the BAS process in stravismus situation realizes sub-aperture stitching: carry out orientation Scaling at range-Dopler domain, then sub-aperture stitching, carries out De-rotation and orientation obtains final SAR image to compression to the full aperture data obtained.

Look side ways the further prioritization scheme of sub-aperture wavenumber domain formation method of Sliding spotlight SAR as the present invention, described step 2) concrete steps as follows:

Step 2.1), pulse compression is carried out to echo data, obtains distance frequency domain, orientation time domain data;

Step 2.2), orientation is carried out to Fourier transform to data after pulse pressure, obtains two-dimensional frequency data;

Step 2.3), complete consistent compression in two-dimensional frequency, realize first main focus steps, the expression formula of reference function is:

$H_1=\exp \left\{j\frac{4\mathrm{\π}}{c}{R}_{\mathrm{ref}}\right[\sqrt{{(f_{\mathrm{\τ}}+f_c)}^2-{\left(\frac{f_{a}c}{2V_a}\right)}^2}\cos {\mathrm{\θ}}_s+\frac{f_{a}c}{{2V}_a}\sin {\mathrm{\θ}}_s\left]\right\}$

Wherein, H ₁for the expression formula of reference function, j is the base unit of imaginary number, R _ref=R0/cos θ _sfor reference distance, f _τand f _abe respectively distance to orientation to frequency, f _cfor radar center frequency, c is the light velocity, V _afor radar bearing is to speed, θ _sfor angle of squint;

Step 2.4), complete Stolt interpolation in two-dimensional frequency, realize the focusing of non-reference distance point target, Stolt interpolation makes original frequency of distance f by substitution of variable _τbe mapped as new frequency of distance f _τ', its formula is as follows:

$\sqrt{{(f_{\mathrm{\τ}}+f_c)}^2-{\left(\frac{f_{a}c}{{2V}_a}\right)}^2}\cos {\mathrm{\θ}}_s+\frac{f_{a}c}{{2V}_a}\sin {\mathrm{\θ}}_s=f_c+f_{\mathrm{\τ}}^{\′};$

Step 2.5), eliminate orientation to skew, and distance is moved to reference distance place to time centre, be specially the data after by Stolt interpolation and be multiplied by following phase function:

$H_2=\exp \{-j\frac{2\mathrm{\π}{f}_a{R}_{\mathrm{ref}}}{V_a}\sin {\mathrm{\θ}}_s-j\frac{4\mathrm{\π}(f_c+f_{\mathrm{\τ}}^{\′})R_{\mathrm{ref}}}{c}\}$

Wherein, H ₂for the expression formula of phase function;

Step 2.6), distance, to IFFT, is transformed into range-Dopler domain.

Look side ways the further prioritization scheme of sub-aperture wavenumber domain formation method of Sliding spotlight SAR as the present invention, described step 3) concrete steps as follows:

Step 3.1), be multiplied by the orientation Scaling factor at range-Dopler domain:

$H_3=\exp \{j2\mathrm{\π}{t}_v{f}_a+j\frac{{\mathrm{\πf}}_a^2}{K_{\mathrm{scl}}\left(r\right)}\}$

Wherein, H ₃for the orientation Scaling factor, r is distance axis, $t_v=\frac{\mathrm{\λr}{f}_{\mathrm{dc}}\cos \left({\mathrm{\θ}}_s\right)}{{2V}_a^2\sqrt{1-{\left(\frac{\mathrm{\λ}{f}_{\mathrm{dc}}}{{2V}_a}\right)}^2}},K_{\mathrm{scl}}=\frac{{2V}_a^2{\cos }^2{\mathrm{\θ}}_s}{\mathrm{\λr}},$ λ is wavelength, f _dc=2V _asin θ _s/ λ is full aperture doppler centroid;

Step 3.2), orientation is transformed into orientation time domain to inverse Fourier transform, carries out sub-aperture stitching and obtains full aperture data, comprise following concrete steps in orientation time domain:

Step 3.2.1), definition N _a× N _rthe full aperture matrix of size, by the N of first sub-aperture _aiindividual pulse is assigned to the front N of full aperture matrix _aiindividual pulse;

Step 3.2.2), calculate orientation to overlaid pixel unit Δ N=kN _ai, successively the Δ N/2+1 of i-th (i > 1) individual sub-aperture is walked to N _aithe N of row _ai-Δ N/2-1 pulse is assigned to (i-1) (N of full aperture _ai-Δ N)+Δ N/2+1 walks to (i-1) (N _ai-Δ N)+N _aioK, complete the splicing of sub-aperture, wherein, k is overlap ratio;

Step 3.3), N is respectively mended to the left and right in full aperture matrix orientation _a/ 2 zero, comprise following concrete steps:

Step 3.3.1), definition N' _athe new matrix of × Nr size, wherein, N' _a=2N _a;

Step 3.3.2), original matrix is assigned to the N of new matrix _a/ 2+1 walks to N' _a-N _a/ 2 row, complete orientation to zero padding;

Step 3.4), full aperture orientation is to De-rotation:

$H_4=\exp \{\mathrm{j\π}{K}_{\mathrm{rot}}{t}_{a\_\mathrm{all}}^2-j2\mathrm{\π}{f}_{\mathrm{dc}\_\mathrm{all}}{t}_{a\_\mathrm{all}}\}$

Wherein, H ₄the fixed phase of De-rotation, $K_{\mathrm{rot}}=\frac{{2V}_a^2{\cos }^3{\mathrm{\θ}}_s}{\mathrm{\λ}{R}_{\mathrm{rot}}},R_{\mathrm{rot}}=\frac{R_0}{1-V_f/V_a},$ V _ffor beam district sliding speed, t _{a_all}and f _{dc_all}be respectively full aperture orientation to time and orientation to centre frequency;

Step 3.5), orientation is to Fourier transform, and carry out orientation to pulse pressure at orientation frequency domain, the pulse pressure factor is:

$H_5=\exp \left\{j\frac{{\mathrm{\πf}}_a^2}{K_{\mathrm{eff}}\left(r\right)}\right\}$

Wherein, H ₅for the pulse pressure factor, K _eff(r)=K _rot-K _scl(r).

Step 3.6), orientation obtains full aperture SAR image to inverse Fourier transform.

Look side ways the further prioritization scheme of sub-aperture wavenumber domain formation method of Sliding spotlight SAR as the present invention, step 1) described in sub-aperture size be:

$T_{\mathrm{sub}}\≤\frac{\mathrm{PRF}-\underset{\mathrm{\θ}}{\max }{B}_{a,\mathrm{proc}}}{\left|K_{\mathrm{rot}}\right|}$

Wherein, T _subfor the size of the sub-aperture of division, PRF is azimuth sample rate, B _{a, proc}the orientation bandwidth of single sub-aperture.

The present invention adopts above technical scheme compared with prior art, has following technique effect:

1. overcome the problem that the data volume of stravismus Sliding spotlight SAR existence is large;

2. overcome the problem of orientation Doppler center non-zero;

3. overcome the problem that doppler bandwidth is excessive.

Accompanying drawing explanation

Fig. 1 is stravismus Sliding spotlight SAR geometric model;

Fig. 2 is method flow diagram;

The point target simulation result that Fig. 3 is angle of squint when being 0 °;

The point target simulation result that Fig. 4 is angle of squint when being 20 °;

The point target simulation result that Fig. 5 is angle of squint when being 30 °;

The point target simulation result that Fig. 6 is angle of squint when being 40 °.

Embodiment

Below in conjunction with accompanying drawing, technical scheme of the present invention is described in further detail:

The present embodiment utilizes SAR emulated data make checking to this method and analyze, emulated data arranges as follows: radar bandwidth is 300MHz, carrier frequency is 10GHz, wide during signal is 20 μ s, impulse sampling frequency is 360MHz, pulse repetition rate PRF is 1000Hz, and the carrier aircraft speed of a ship or plane is 120m/s, the translational speed of antenna irradiated site on ground is 60m/s, and carrier aircraft height is 10km.SAR emulated data orientation is to sampling number N _rbe 16384, distance is to sampling number N _abe 16384, the orientation of single sub-aperture is to sampling number N _aibe 8192, angle of squint is got 0 °, 20 °, 30 °, 40 ° respectively and is emulated.

With reference to Fig. 1, Fig. 2, flying platform speed is V _a, radar beam center on ground with at the uniform velocity V _gscanning, O and O ' is respectively aperture center and scene center point, O _rotfor rotary middle point, θ _sfor angle of squint, R ₀and R _rotbe respectively aperture to scene bee-line and aperture to rotation center bee-line.P is scene any point, and the sub-aperture wavenumber domain formation method of stravismus Sliding spotlight SAR comprises the steps:

Step 1: by N _a× N _rfull aperture radar return data overlap be divided into several sub-aperture, each sub-aperture echo data is N _ai× N _r, wherein N _a=16384 is full aperture radar echo pulse number, N _rfor distance is to sampling number, N _ai=8192 is each sub-aperture radar echo pulse number, if the overlap ratio of sub-aperture is 1/4, then the sub-aperture number divided is 2.

Step 2: the imaging of expansion wavenumber domain method is carried out to i-th sub-aperture echo data, comprises following concrete steps:

Step 2-1: carry out pulse compression to echo data, obtains orientation time domain, distance frequency domain data;

Step 2-2: orientation is carried out to Fourier transform to data after pulse pressure, obtains two-dimensional frequency data;

Step 2-3: complete consistent compression in two-dimensional frequency, realizes first main focus steps.The expression formula of reference function is as shown in (1)

$H_1=\exp \left\{j\frac{4\mathrm{\π}}{c}{R}_{\mathrm{ref}}\right[\sqrt{{(f_{\mathrm{\τ}}+f_c)}^2-{\left(\frac{f_{a}c}{2V_a}\right)}^2}\cos {\mathrm{\θ}}_s+\frac{f_{a}c}{{2V}_a}\sin {\mathrm{\θ}}_s\left]\right\}---\left(1\right)$

Wherein, R _ref=R0/cos (θ _s) be reference distance, f _τand f _abe respectively distance to orientation to frequency, f _c=10GHz is radar center frequency, c=3 × 10 ⁸for the light velocity, V _a=120m/s be radar bearing to speed, θ _sfor angle of squint.

Step 2-4: complete Stolt interpolation in two-dimensional frequency, realizes the focusing of the point target of non-reference distance.

Stolt interpolation makes original frequency of distance f by substitution of variable _τbecome new frequency of distance f _τ'

$\sqrt{{(f_{\mathrm{\τ}}+f_c)}^2-{\left(\frac{f_{a}c}{{2V}_a}\right)}^2}\cos {\mathrm{\θ}}_s+\frac{f_{a}c}{{2V}_a}\sin {\mathrm{\θ}}_s=f_c+f_{\mathrm{\τ}}^{\′};---\left(2\right)$

Step 2-5: in order to sub-aperture stitching below, needs the formula that is multiplied by (3)

$H_2=\exp \{-j\frac{2\mathrm{\π}{f}_a{R}_{\mathrm{ref}}}{V_a}\sin {\mathrm{\θ}}_s-j\frac{4\mathrm{\π}(f_c+f_{\mathrm{\τ}}^{\′})R_{\mathrm{ref}}}{c}\}---\left(3\right)$

Wherein Section 1 eliminates orientation to skew, and distance is moved to reference distance place to time centre by Section 2.

Step 2-6: distance, to IFFT, is transformed into range-Dopler domain.

Step 3: the BAS process of stravismus situation, comprises following concrete steps:

Step 3-1: be multiplied by the orientation Scaling factor at range-Dopler domain.

$H_3=\exp \{j2\mathrm{\π}{t}_v{f}_a+j\frac{{\mathrm{\πf}}_a^2}{K_{\mathrm{scl}}\left(r\right)}\}---\left(4\right)$

Wherein, r is distance axis, $t_v=\frac{\mathrm{\λr}{f}_{\mathrm{dc}}\cos \left({\mathrm{\θ}}_s\right)}{{2V}_a^2\sqrt{1-{\left(\frac{\mathrm{\λ}{f}_{\mathrm{dc}}}{{2V}_a}\right)}^2}},K_{\mathrm{scl}}=\frac{{2V}_a^2{\cos }^2{\mathrm{\θ}}_s}{\mathrm{\λr}}.$

Step 3-2: orientation is transformed into orientation time domain to inverse Fourier transform, carries out sub-aperture stitching in orientation time domain and obtains full aperture data.Comprise following concrete steps:

Step 3-2-1: 8192 of first sub-aperture pulses are assigned to front 8192 pulses of full aperture matrix by the full aperture matrix of definition 16384 × 16384 sizes.

Step 3-2-2: note orientation to overlaid pixel unit Δ N=2048.7168 pulses walking to the 8192nd row by the 1025th of the 2nd sub-aperture the are assigned to the 8193rd of full aperture battle array and walk to the 15360th, complete the splicing of sub-aperture.

Step 3-3: full aperture matrix orientation respectively mends 8192 zero to the left and right.Comprise following concrete steps:

Step 3-3-1: establish N' _a=32768, the new matrix of definition 32768 × 16384 sizes.

Step 3-3-2: original matrix is assigned to the 8193rd of new matrix and walks to the 24576th row, complete orientation to zero padding.

Step 3-4: full aperture orientation is to De-rotation.

$H_4=\exp \{\mathrm{j\π}{K}_{\mathrm{rot}}{t}_{a\_\mathrm{all}}^2-j2\mathrm{\π}{f}_{\mathrm{dc}\_\mathrm{all}}{t}_{a\_\mathrm{all}}\}---\left(5\right)$

Wherein, $K_{\mathrm{rot}}=\frac{{2V}_a^2{\cos }^3{\mathrm{\θ}}_s}{\mathrm{\λ}{R}_{\mathrm{rot}}},R_{\mathrm{rot}}=\frac{R_0}{1-V_f/V_a},$ V _f=60m/s is the translational speed of antenna irradiated site on ground, t _{a_all}and f _{dc_all}be respectively full aperture orientation to time and orientation to centre frequency.

Step 3-5: orientation is to Fourier transform, and carry out orientation to pulse pressure at orientation frequency domain, the pulse pressure factor is:

$H_5=\exp \left\{j\frac{{\mathrm{\πf}}_a^2}{K_{\mathrm{eff}}\left(r\right)}\right\}---\left(6\right)$

Wherein, K _eff(r)=K _rot-K _scl(r).

Step 3-6: orientation obtains full aperture SAR image to inverse Fourier transform.Fig. 3,4,5,6 sets forth point target simulation result when angle of squint is 0 °, 20 °, 30 °, 40 °.

Further, the sub-aperture size described in step 1 is:

$T_{\mathrm{sub}}\≤\frac{\mathrm{PRF}-\underset{\mathrm{\θ}}{\max }{B}_{a,\mathrm{proc}}}{\left|K_{\mathrm{rot}}\right|}---\left(7\right)$

Wherein, PRF is azimuth sample rate, B _{a, proc}the orientation bandwidth of single sub-aperture.

The above is only the preferred embodiment of the present invention, not does any pro forma restriction to the present invention.Should be understood that; any those skilled in the art; do not departing from technical solution of the present invention scope; according to technical spirit of the present invention; within spirit of the present invention and principle thereof; the any simple amendment that above embodiment is done, equivalently replace and improve, within the protection domain all belonging to technical solution of the present invention.

Claims (4)

1. look side ways the sub-aperture wavenumber domain formation method of Sliding spotlight SAR, it is characterized in that, comprise the steps:

Step 1), by N _a× N _rfull aperture radar return data overlap be divided into several sub-aperture, each sub-aperture echo data is N _ai× N _r, and according to dividing the size determination sub-aperture number of lap between the size of sub-aperture and any two sub-aperture: the value rounded off to negative direction adds 1;

Wherein, N _afor full aperture radar echo pulse number, N _rfor distance is to sampling number, N _aifor each sub-aperture echo-pulse number, i is the index of sub-aperture, and Δ N is the size of lap between described two sub-aperture;

Step 2), expansion space virtual detection techniques is used respectively to the sub-aperture divided: first orientation is carried out to FFT to the sub-aperture echo data after pulse pressure, then carry out consistent compression and Stolt interpolation in two-dimensional frequency, last length obtains basic imaging results as IFFT;

Step 3), the BAS process in stravismus situation realizes sub-aperture stitching: carry out orientation Scaling at range-Dopler domain, then sub-aperture stitching, carries out De-rotation and orientation obtains final SAR image to compression to the full aperture data obtained.

2. the sub-aperture wavenumber domain formation method of stravismus Sliding spotlight SAR according to claim 1, is characterized in that, described step 2) concrete steps as follows:

Step 2.1), pulse compression is carried out to echo data, obtains distance frequency domain, orientation time domain data;

Step 2.2), orientation is carried out to Fourier transform to data after pulse pressure, obtains two-dimensional frequency data;

Step 2.3), complete consistent compression in two-dimensional frequency, realize first main focus steps, the expression formula of reference function is:

$H_1=\exp \left\{j\frac{4\mathrm{\π}}{c}{R}_{\mathrm{ref}}\right[\sqrt{{(f_{\mathrm{\τ}}+f_c)}^2-{\left(\frac{f_{a}c}{2V_a}\right)}^2}\cos {\mathrm{\θ}}_s+\frac{f_{a}c}{2V_a}\sin {\mathrm{\θ}}_s\left]\right\}$

Wherein, H ₁for the expression formula of reference function, j is the base unit of imaginary number, R _ref=R0/cos θ _sfor reference distance, f _τand f _abe respectively distance to orientation to frequency, f _cfor radar center frequency, c is the light velocity, V _afor radar bearing is to speed, θ _sfor angle of squint;

Step 2.4), complete Stolt interpolation in two-dimensional frequency, realize the focusing of non-reference distance point target, Stolt interpolation makes original frequency of distance f by substitution of variable _τbe mapped as new frequency of distance f _τ', its formula is as follows:

$\sqrt{{(f_{\mathrm{\τ}}+f_c)}^2-{\left(\frac{f_{a}c}{2V_a}\right)}^2}\cos {\mathrm{\θ}}_s+\frac{f_{a}c}{2V_a}\sin {\mathrm{\θ}}_s=f_c+{f_{\mathrm{\τ}}}^{\′};$

Step 2.5), eliminate orientation to skew, and distance is moved to reference distance place to time centre, be specially the data after by Stolt interpolation and be multiplied by following phase function:

$H_2=\exp \{-j\frac{2\mathrm{\π}{f}_a{R}_{\mathrm{ref}}}{V_a}\sin {\mathrm{\θ}}_s-j\frac{4\mathrm{\π}(f_c+{f_{\mathrm{\τ}}}^{\′})R_{\mathrm{ref}}}{c}\}$

Wherein, H ₂for the expression formula of phase function;

Step 2.6), distance, to IFFT, is transformed into range-Dopler domain.

3. the sub-aperture wavenumber domain formation method of stravismus Sliding spotlight SAR according to claim 2, is characterized in that, described step 3) concrete steps as follows:

Step 3.1), be multiplied by the orientation Scaling factor at range-Dopler domain:

$H_3=\exp \{j2\mathrm{\π}{t}_v{f}_a+j\frac{\mathrm{\π}{f}_a^2}{K_{\mathrm{scl}}\left(r\right)}\}$

Wherein, H ₃for the orientation Scaling factor, r is distance axis, $t_v=\frac{\mathrm{\λr}{f}_{\mathrm{dc}}\cos \left({\mathrm{\θ}}_s\right)}{2V_a^2\sqrt{1-{\left(\frac{\mathrm{\λ}{f}_{\mathrm{dc}}}{2V_a}\right)}^2}},K_{\mathrm{scl}}=\frac{2V_a^2{\cos }^2{\mathrm{\θ}}_s}{\mathrm{\λr}},$ λ is wavelength, f _dc=2V _asin θ _s/ λ is full aperture doppler centroid;

Step 3.2), orientation is transformed into orientation time domain to inverse Fourier transform, carries out sub-aperture stitching and obtains full aperture data, comprise following concrete steps in orientation time domain:

Step 3.2.1), definition N _a× N _rthe full aperture matrix of size, by the N of first sub-aperture _aiindividual pulse is assigned to the front N of full aperture matrix _aiindividual pulse;

Step 3.2.2), calculate orientation to overlaid pixel unit Δ N=kN _ai, successively the Δ N/2+1 of i-th (i > 1) individual sub-aperture is walked to N _aithe N of row _ai-Δ N/2-1 pulse is assigned to (i-1) (N of full aperture _ai-Δ N)+Δ N/2+1 walks to (i-1) (N _ai-Δ N)+N _aioK, complete the splicing of sub-aperture, wherein, k is overlap ratio;

Step 3.3), N is respectively mended to the left and right in full aperture matrix orientation _a/ 2 zero, comprise following concrete steps:

Step 3.3.1), definition N' _athe new matrix of × Nr size, wherein, N' _a=2N _a;

Step 3.3.2), original matrix is assigned to the N of new matrix _a/ 2+1 walks to N' _a-N _a/ 2 row, complete orientation to zero padding;

Step 3.4), full aperture orientation is to De-rotation:

$H_4=\exp \{\mathrm{j\π}{K}_{\mathrm{rot}}{t}_{a\_\mathrm{all}}^2-j2\mathrm{\π}{f}_{\mathrm{dc}\_\mathrm{all}}{t}_{a\_\mathrm{all}}\}$

Wherein, H ₄the fixed phase of De-rotation, v _ffor beam district sliding speed, t _{a_all}and f _{dc_all}be respectively full aperture orientation to time and orientation to centre frequency;

Step 3.5), orientation is to Fourier transform, and carry out orientation to pulse pressure at orientation frequency domain, the pulse pressure factor is:

$H_5=\exp \left\{j\frac{\mathrm{\π}{f}_a^2}{K_{\mathrm{eff}}\left(r\right)}\right\}$

Wherein, H ₅for the pulse pressure factor, K _eff(r)=K _rot-K _scl(r).

Step 3.6), orientation obtains full aperture SAR image to inverse Fourier transform.

4. the sub-aperture wavenumber domain formation method of stravismus Sliding spotlight SAR according to claim 3, is characterized in that, step 1) described in sub-aperture size be:

$T_{\mathrm{sub}}\≤\frac{\mathrm{PRF}-\underset{\mathrm{\θ}}{\max }{B}_{a,\mathrm{proc}}}{\left|K_{\mathrm{rot}}\right|}$

Wherein, T _subfor the size of the sub-aperture of division, PRF is azimuth sample rate, B _{a, proc}the orientation bandwidth of single sub-aperture.