Large squint bunching SAR wave number domain imaging processing method based on sliding window data receiving

Abstract

The invention discloses a large squint bunching SAR wave number domain imaging processing method based on sliding window receiving data, and the method comprises the steps: firstly carrying out the preprocessing of two-dimensional time domain data received by a sliding window, and obtaining two-dimensional wave number domain echo data; multiplying the two-dimensional wavenumber domain echo by a reference function to realize complete focusing at a reference distance; secondly, two-dimensional coupling brought by the sliding window receiving mode is decoupled through a two-dimensional fast separable interpolation method, namely orientation interpolation and distance interpolation are carried out in sequence (the sequence is not limited); and finally, the decoupled echo signal is converted to an image domain by adopting two-dimensional fast Fourier inverse transform, so that a two-dimensional high-resolution focused image of the target is obtained. According to the method, the problem of low frequency domain sampling efficiency caused by two-dimensional spectrum distortion in a high squint mode is solved, and the processing efficiency of eliminating two-dimensional coupling in a sliding receiving window mode can be improved at the same time.

Description

Technical Field

[0001] The invention belongs to the technical field of radar imaging, and in particular relates to a wavenumber domain imaging processing method for a high squint spotlight SAR based on sliding window data reception. Background Art

[0002] High resolution has always been a core concern in the field of synthetic aperture radar (SAR) imaging technology. For the strip mode, its azimuth resolution is limited by the length of the synthetic aperture determined by the azimuth antenna beam width, which is usually no more than half the antenna length. In contrast, the beamforming mode controls the antenna beam pointing so that the radar beam continues to illuminate the same target area along the moving track, thereby breaking through the antenna beam width limitation, achieving a longer synthetic aperture, and obtaining higher azimuth resolution.

[0003] Among the spotlight SAR imaging algorithms, the range Doppler algorithm (RDA), polar format algorithm (PFA) and range migration algorithm (RMA) are all the current mainstream technologies. Among them, the range migration algorithm (RMA), as a frequency domain processing algorithm, transforms the signal into a two-dimensional frequency domain for processing, so it is more efficient than the time domain algorithm. At the same time, since its processing process does not introduce approximate processing, it ensures high imaging accuracy, thus having a significant advantage in imaging resolution.

[0004] In recent years, with the continuous expansion of radar detection range and the increasing demand for target dwell time, various SAR platforms tend to adopt high squint imaging technology. However, the high squint working mode brings multiple challenges in data acquisition and imaging signal processing. Especially under high squint conditions, the target range migration is significantly aggravated, resulting in more serious two-dimensional coupling of echo signals, which not only reduces the acquisition efficiency of echo data, but also greatly increases the complexity of subsequent imaging signal processing. At the data acquisition level, if the traditional fixed sampling window method is used, in order to ensure the complete acquisition of echo signals, the sampling window length needs to be greatly increased, and the collected data contains a large amount of invalid information, which is bound to lead to a significant reduction in sampling efficiency. In addition, the severe coupling of the signal also makes the derivation of the two-dimensional analytical spectrum more difficult, and the time domain coupling further leads to irregular spectrum support area, which in turn affects the efficiency of frequency domain sampling. Summary of the invention

[0005] Purpose of the invention: In view of the above problems, the present invention proposes a wavenumber domain imaging processing method for a high-squint spotlight SAR based on sliding window received data, which solves the problem of low frequency domain sampling efficiency caused by two-dimensional spectrum distortion in the high-squint mode and can simultaneously improve the processing efficiency of eliminating two-dimensional coupling in the sliding receiving window mode.

[0006] Technical solution: To achieve the purpose of the present invention, the technical solution adopted by the present invention is:

[0007] A wavenumber domain imaging processing method for high squint spotlight SAR based on sliding window received data comprises the following steps:

[0008] Step 1: Preprocess the two-dimensional time domain data received by the sliding window to obtain processed two-dimensional wavenumber domain echo data;

[0009] Step 2: Multiply the two-dimensional wavenumber domain echo with the reference function to achieve complete focusing at the reference distance;

[0010] Step 3: Use a two-dimensional fast separable interpolation method to decouple the two-dimensional coupling caused by the sliding window receiving mode to obtain a decoupled two-dimensional frequency domain echo signal;

[0011] Step 4: Use the two-dimensional inverse fast Fourier transform to convert the decoupled echo signal from the two-dimensional frequency domain to the image domain to obtain a high-resolution focused image of the target.

[0012] Further, step 1 pre-processes the two-dimensional time domain echo data received by the sliding window to obtain processed two-dimensional wave number domain echo data, including: performing range Fourier transform, range matched filtering, azimuth Fourier transform on the sliding window received data in sequence and transforming it into a wave number domain form. This is achieved through the following process:

[0013] The expression of sliding window receiving two-dimensional time domain echo data is:

[0014]

[0015] Among them, s slide (t a ,t r ) is the sliding window receiving two-dimensional time domain echo, A slide (t a ,t r ) is the time domain envelope in sliding window mode, t r is the distance-to-speed time, t a is the azimuth time, f c is the carrier frequency, k r is the distance modulation frequency, c is the speed of light, (-x 0 ,-y 0 ) is the reference coordinate of radar S, and there is a point target P(x t ,y t ), R t is the instantaneous distance from the target P to the radar S, v is the radar running speed, and θ is the oblique angle.

[0016] After range Fourier transform, range matched filtering and spectrum center shift, ignoring amplitude changes, the echo expression is:

[0017]

[0018] Among them, s slide (t a ,f r ) is the sliding window receiving distance, time domain, azimuth and frequency domain echo, f r is the distance frequency;

[0019] After the center of the spectrum is moved and the azimuth Fourier transform is performed, the expression of the two-dimensional wavenumber domain signal is:

[0020]

[0021] Among them, s slide (K x ,K r ) is the sliding window receiving two-dimensional wavenumber domain echo, K x , K r are defined as the wave numbers in azimuth and range directions respectively, and the expressions are:

[0022]

[0023] where f r is the distance frequency, f a is the azimuth frequency, K rc is the distance to the wave number center, and its value is

[0024] Furthermore, in step 2, the two-dimensional wavenumber domain echo is multiplied by a reference function, and the reference function is:

[0025]

[0026] Among them, R 0 is the radar reference distance, at this time, the echo expression becomes:

[0027]

[0028] In the formula, s' slide (K x ,K r ) is the two-dimensional wavenumber domain echo signal after multiplying with the reference function.

[0029] Furthermore, in step three, a two-dimensional fast separable interpolation method is used to decouple the two-dimensional coupling caused by the sliding window receiving mode. The interpolation direction selected is interpolation along the line of sight to simplify the amount of interpolation data, specifically:

[0030] Rotate the scene coordinate system, choose to interpolate along the line of sight, and transform the echo expression into:

[0031] s s ' lide (K x,K r )=exp[-jG y (K x ,K r )·y t ']·exp[-jG x (K x ,K r )·x t '],

[0032] Among them, x t ',y t ' are the coordinates of the target point in the line of sight coordinate system, G x (K x ,K r ), G y (K x ,K r ) are the wavenumber transformation expressions in azimuth and distance, respectively;

[0033]

[0034] The signal has two-dimensional coupling. If two-dimensional decoupling is required, the following variable replacements need to be completed:

[0035]

[0036] At the same time, in order to facilitate the subsequent steps, the above formula is reversed to obtain:

[0037]

[0038] Among them, H x (K″ x ,K″ y ), H r (K″ x ,K″ y ) are K x , K r About K' x and K″ y The function expression of .

[0039] Furthermore, in step 3, the echo multiplied by the reference function is interpolated in azimuth and range, which is denoted as Interp 1a2r ,Interp 1a2r The interpolation method uses azimuth interpolation to make the sampling points in K″ x -K r The coordinate system is evenly distributed, specifically:

[0040] In K″ x -K r Coordinate system setting K″x Uniformly distributed coordinate points, and then according to K″ x =G x (K x ,K r ) Inverse solution to obtain these points in K x -K r K of the mapping point of the coordinate system x The coordinate values ​​are:

[0041]

[0042] Among them, m x (K″ x ,K r ) is K x About K″ x and K r Function expression of ;

[0043] After obtaining the coordinates of the mapping points in each row, the echo data values ​​of the mapping points are returned to K″ row by row through interpolation. x -K r Coordinate system. After all rows are interpolated, the echo sampling point is at K″ x -K r The coordinate system is uniformly distributed, and the echo expression becomes:

[0044] s 11 '(K″ x ,K r )=exp(-jK″ x ·x t ')·exp[-j·h y (K″ x ,K r )·y t '],

[0045] Among them, s 11 '(K″ x ,K r ) is the two-dimensional wavenumber domain echo signal after azimuth interpolation, h y (K″ x ,K r ) is K″ y About K″ x -K r The expression of K r =H r (K″ x ,K″ y ) is inversely solved, specifically:

[0046]

[0047] Then, through distance interpolation, the sampling point is finally placed at K″ x -K″ y The coordinate system becomes a two-dimensional uniform distribution, achieving the same purpose as traditional two-dimensional interpolation. Specifically:

[0048] In K″ x -K″ y The coordinate system is along each column K″ x Setting K″ y Uniformly distributed coordinate points, according to K″ x , K″ y With K r The relationship K r =H r (K″ x ,K″ y ) Calculate the coordinate point set at K″ x -K r Mapping point K in the coordinate system r After obtaining the coordinates of the mapping points in each column, the echo data of the mapping points are returned to K″ column by column through interpolation. x -K″ y Coordinate system. After all columns are interpolated, the echo sampling point is at K″ x -K″ y At this time, the echo expression becomes:

[0049] s' slide (K″ x ,K″ y )=exp(-jK″ y ·y t ')·exp(-jK″ x ·x t '),

[0050] Among them, s' slide (K″ x ,K″ y ) is the two-dimensional wavenumber domain echo signal after two-dimensional decoupling.

[0051] Furthermore, in step 3, the echo multiplied by the reference function is interpolated in range and azimuth, which is denoted as Interp 1r2a ,Interp 1r2a The interpolation method uses distance interpolation to make the sampling points in K x -K″ y The coordinate system is evenly distributed, specifically:

[0052] In K x -K″ y Coordinate system setting K″ y Uniformly distributed coordinate points, and then according to K″y =G y (K x ,K r ) Inverse solution to obtain these points in K x -K r K of the mapping point of the coordinate system r The coordinate values ​​are:

[0053]

[0054] Among them, m r (K x ,K″ y ) is K r About K x and K' y Function expression of ;

[0055] After obtaining the coordinates of the mapping points in each column, the echo data of the mapping points are returned to K column by column through interpolation. x -K″ y Coordinate system. After all columns are interpolated, the echo sampling point is at K x -K″ y The coordinate system is evenly distributed, and the echo expression becomes:

[0056] s 12 '(K x ,K″ y ) = exp(-jK″ y ·y t ')·exp[-j·h x (K x ,K″ y )·x t '],

[0057] Among them, s 12 '(K x ,K″ y ) is the two-dimensional wavenumber domain echo signal after completing the distance interpolation, h x (K x ,K″ y ) is K″ x About K x -K″ y The expression of K x =H x (K″ x ,K″ y ) is inversely solved, specifically:

[0058]

[0059] Then, through azimuth interpolation, the sampling point is finally located at K″ x -K″y The coordinate system becomes a two-dimensional uniform distribution, achieving the same purpose as traditional two-dimensional interpolation, specifically:

[0060] In K″ x -K″ y The coordinate system is along each row K″ y Setting K″ x Uniformly distributed coordinate points, according to K″ x , K″ y With K x The relationship K x =H x (K″ x ,K″ y ) Calculate the coordinate point set in K x -K″ y The coordinates of the mapping points in the coordinate system. After obtaining the coordinates of the mapping points in each row, the echo data of the mapping points are returned to K″ row by row through interpolation. x -K″ y Coordinate system. After all rows are interpolated, the echo sampling point is at K″ x -K″ y The coordinate system achieves uniform distribution, and the echo expression becomes s' slide (K″ x ,K″ y ).

[0061] Beneficial effects: Compared with the prior art, the technical solution of the present invention has the following beneficial technical effects:

[0062] The wavenumber domain imaging processing method of the highly squint spotlight SAR based on sliding window received data proposed in the present invention solves the problem of low frequency domain sampling efficiency caused by two-dimensional spectrum distortion in the highly squint mode, and can also improve the processing efficiency of eliminating two-dimensional coupling in the sliding receiving window mode, which has great practicality in processing large amounts of data in actual engineering. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] Figure 1 Flow chart of the method of the present invention.

[0064] Figure 2 The figure is a schematic diagram of the geometric relationship of the spotlight synthetic aperture radar data acquisition in the method of the present invention.

[0065] Figure 3 In the method of the present invention, 1a2r Schematic diagram of the azimuthal interpolation process of the interpolation method.

[0066] Figure 4 In the method of the present invention, 1a2r Schematic diagram of the distance interpolation process of the interpolation method.

[0067] Figure 5 In the method of the present invention, 1r2a Schematic diagram of the distance interpolation process of the interpolation method.

[0068] Figure 6 In the method of the present invention, 1r2a Schematic diagram of the azimuthal interpolation process of the interpolation method. DETAILED DESCRIPTION

[0069] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0070] In a specific embodiment of the present invention, Figure 1 A wavenumber domain imaging processing method for a high squint spotlight SAR based on sliding window received data is provided, and the method is described by taking the application of the method to a terminal as an example, comprising the following steps:

[0071] Step 1: Preprocess the two-dimensional time domain data received by the sliding window to obtain processed two-dimensional wavenumber domain echo data.

[0072] Among them, by preprocessing the two-dimensional time domain data received by the sliding window, the data received by the sliding window can be sequentially implemented by performing distance Fourier transform, distance matched filtering, azimuth Fourier transform and transforming them into wave number domain forms.

[0073] In a specific embodiment of the present invention, the geometric relationship of spaceborne synthetic aperture radar data collection is as follows: Figure 2 As shown in the figure, the coordinate system is established with the scene center O as the origin, the X axis parallel to the radar movement direction, and the Y axis perpendicular to the radar movement direction. The reference coordinate of radar S is (-x 0 ,-y 0 ), t a is the azimuth time, assuming it moves along the positive direction of the X axis at a constant speed v, t a After time, the radar coordinates become (-x 0 +vt a ,-y 0 ). c is the instantaneous distance from the radar to the center of the scene, R 0 is the reference distance, θ is the oblique angle. There is a point target P(x t ,y t ), R t is the instantaneous distance from the target P to the radar.

[0074] according to Figure 2 The geometric relationship can be obtained:

[0075]

[0076] Among them, t a is the azimuth time.

[0077] x 0 =R 0 sinθ,y 0 =R 0 ·cosθ,

[0078] The expression of sliding window receiving two-dimensional time domain echo data is:

[0079]

[0080] Among them, s slide (t a ,t r ) is the sliding window receiving two-dimensional time domain echo, A slide (t a ,t r ) is the time domain envelope in sliding window mode, t r is the distance to fast time, f c is the carrier frequency, k r is the distance modulation frequency, and c is the speed of light.

[0081] After distance Fourier transform, distance matched filtering and spectrum center shift, ignoring the amplitude change, the echo expression is:

[0082]

[0083] Among them, s slide (t a ,f r ) is the sliding window receiving distance, time domain, azimuth and frequency domain echo, f r is the distance frequency.

[0084] After moving the center of the spectrum and performing azimuth Fourier transform, the expression of the two-dimensional wavenumber domain signal is:

[0085]

[0086] Among them, s slide (K x ,K r ) is the sliding window receiving two-dimensional wavenumber domain echo, K x , K r are defined as the wave numbers in azimuth and distance directions respectively, and their expressions are:

[0087]

[0088] where f ris the distance frequency, f a is the azimuth frequency, K rc is the distance to the wave number center, and its value is

[0089] Step 2: Multiply the two-dimensional wavenumber domain echo with the reference function to achieve complete focusing at the reference distance.

[0090] Multiply the two-dimensional wavenumber domain echo by the reference function, which is:

[0091]

[0092] Among them, R 0 is the radar reference distance, at this time, the echo expression becomes:

[0093]

[0094] In the formula, s' slide (K x ,K r ) is the two-dimensional wavenumber domain echo signal after multiplying with the reference function.

[0095] Step 3: Use the two-dimensional fast separable interpolation method to decouple the two-dimensional coupling caused by the sliding window receiving mode.

[0096] Among them, the decoupling of the two-dimensional coupling caused by the sliding window receiving mode using the two-dimensional fast separable interpolation method can be achieved by any of two methods, namely:

[0097] The echo multiplied by the reference function is interpolated in azimuth and range (denoted as Interp 1a2r );

[0098] The echo multiplied by the reference function is interpolated in range and azimuth (denoted as Interp 1r2a ).

[0099] The interpolation direction selected here is interpolation along the line of sight to simplify the amount of interpolation data. Specifically, the scene coordinate system is rotated, interpolation along the line of sight is selected, and the echo expression is deformed.

[0100] s′ slide (K x ,K r )=exp[-jG y (K x ,K r )·y t ']·exp[-jG x (K x ,K r )·xt '],

[0101] Among them, x t ',y t ' are the coordinates of the target point in the line of sight coordinate system, G x (K x ,K r ), G y (K x ,K r ) are the wavenumber transformation expressions in azimuth and distance, respectively;

[0102]

[0103] The above analysis shows that the signal has two-dimensional coupling. If two-dimensional decoupling is required, the following variable replacements need to be completed:

[0104]

[0105] At the same time, in order to facilitate the subsequent steps, the above formula is reversed to obtain:

[0106]

[0107] Among them, H x (K″ x ,K″ y ), H r (K″ x ,K″ y ) are K x , K r About K' x and K″ y The function expression of .

[0108] Step 3 Interp 1a2r Interpolation methods, including:

[0109] In a specific embodiment of the present invention, Figure 3 As shown, the sampling point is K″ through azimuth interpolation. x -K r The coordinate system is evenly distributed, specifically:

[0110] In K″ x -K r Coordinate system setting K″ x Uniformly distributed coordinate points, and then according to K″ x =G x (K x ,K r ) Inverse solution to obtain these points in K x -K r K of the mapping point of the coordinate systemx The coordinate values ​​are:

[0111]

[0112] Among them, m x (K″ x ,K r ) is K x About K″ x and K r The function expression of .

[0113] After obtaining the coordinates of the mapping points in each row, the echo data values ​​of the mapping points are returned to K″ row by row through interpolation. x -K r Coordinate system. After all rows are interpolated, the echo sampling point is at K″ x -K r The coordinate system is uniformly distributed, and the echo expression becomes:

[0114] s 11 '(K″ x ,K r ) = exp(-jK″ x ·x t ')·exp[-j·h y (K″ x ,K r )·y t '],

[0115] Among them, s 11 '(K″ x ,K r ) is the two-dimensional wavenumber domain echo signal after azimuth interpolation, h y (K″ x ,K r ) is K″ y About K″ x -K r The expression of K r =H r (K″ x ,K″ y ) is inversely solved, specifically:

[0116]

[0117] Then through Figure 4 The distance interpolation shown will eventually place the sampling point at K″ x -K″ y The coordinate system becomes a two-dimensional uniform distribution, achieving the same purpose as traditional two-dimensional interpolation. Specifically:

[0118] In K″ x -K″y The coordinate system is along each column K″ x Setting K″ y Uniformly distributed coordinate points, according to K″ x , K″ y With K r The relationship K r =H r (K″ x ,K″ y ) Calculate the coordinate point set at K″ x -K r Mapping point K in the coordinate system r After obtaining the coordinates of the mapping points in each column, the echo data of the mapping points are returned to K″ column by column through interpolation. x -K″ y Coordinate system. After all columns are interpolated, the echo sampling point is at K″ x -K″ y At this time, the echo expression becomes:

[0119] s' slide (K″ x ,K″ y ) = exp(-jK″ y ·y t ')·exp(-jK″ x ·x t '),

[0120] Among them, s' slide (K″ x ,K″ y ) is the two-dimensional wavenumber domain echo signal after two-dimensional decoupling.

[0121] Step 3 Interp 1r2a Interpolation methods, including:

[0122] In a specific embodiment of the present invention, Figure 5 As shown in the figure, the sampling point is interpolated by distance so that x -K″ y The coordinate system is evenly distributed, specifically:

[0123] In K x -K″ y Coordinate system setting K″ y Uniformly distributed coordinate points, and then according to K″ y =G y (K x ,K r ) Inverse solution to obtain these points in K x -K r K of the mapping point of the coordinate system r The coordinate values ​​are:

[0124]

[0125] Among them, m r (K x ,K″ y ) is K r About K x and K' y Function expression of ;

[0126] After obtaining the coordinates of the mapping points in each column, the echo data of the mapping points are returned to K column by column through interpolation. x -K″ y Coordinate system. After all columns are interpolated, the echo sampling point is at K x -K″ y The coordinate system is evenly distributed, and the echo expression becomes:

[0127] s 12 '(K x ,K″ y ) = exp(-jK″ y ·y t ')·exp[-j·h x (K x ,K″ y )·x t ']

[0128] Among them, s 12 '(K x ,K″ y ) is the two-dimensional wavenumber domain echo signal after completing the distance interpolation, h x (K x ,K″ y ) is K″ x About K x -K″ y The expression of K x =H x (K' x ',K″ y ) is inversely solved, specifically:

[0129]

[0130] Then through Figure 6 The azimuth interpolation shown will eventually place the sampling point at K″ x -K″ y The coordinate system becomes a two-dimensional uniform distribution, achieving the same purpose as traditional two-dimensional interpolation, specifically:

[0131] In K″ x -K″ y The coordinate system is along each row K″y Setting K″ x Uniformly distributed coordinate points, according to K″ x , K″ y With K x The relationship K x =H x (K″ x ,K″ y ) Calculate the coordinate point set in K x -K″ y The coordinates of the mapping points in the coordinate system. After obtaining the coordinates of the mapping points in each row, the echo data of the mapping points are returned to K″ row by row through interpolation. x -K″ y Coordinate system. After all rows are interpolated, the echo sampling point is at K″ x -K″ y The coordinate system achieves uniform distribution, and the echo expression becomes s' slide (K″ x ,K″ y ).

[0132] Step 4: Use the two-dimensional inverse fast Fourier transform to perform two-dimensional IFFT processing on the decoupled echo signal, convert it from the two-dimensional frequency domain to the image domain, obtain a high-resolution focused image of the target, and achieve high-resolution focusing of the target.

[0133] It should be understood that although Figure 1 The steps in the flowchart are shown in sequence as indicated by the arrows, but these steps are not necessarily executed in the order indicated by the arrows. Unless otherwise specified in this document, there is no strict order restriction for the execution of these steps, and these steps can be executed in other orders. Moreover, Figure 1 At least part of the steps may include multiple sub-steps or multiple stages. These sub-steps or stages are not necessarily executed at the same time, but can be executed at different times. The execution order of these sub-steps or stages is not necessarily sequential, but can be executed in turn or alternately with other steps or at least part of the sub-steps or stages of other steps.

[0134] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0135] The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the attached claims.

Claims

1. A wavenumber domain imaging processing method for high squint spotlight SAR based on sliding window data reception, characterized in that: The following steps are involved: Step 1: Preprocess the two-dimensional time domain data received by the sliding window to obtain processed two-dimensional wavenumber domain echo data; Step 2: Multiply the two-dimensional wavenumber domain echo with the reference function to achieve complete focusing at the reference distance; Step 3: Use a two-dimensional fast separable interpolation method to decouple the two-dimensional coupling caused by the sliding window receiving mode to obtain a decoupled two-dimensional frequency domain echo signal; Step 4: Use the two-dimensional inverse fast Fourier transform to convert the decoupled echo signal from the two-dimensional frequency domain to the image domain to obtain a high-resolution focused image of the target.

2. The wavenumber domain imaging processing method for high squint spotlight SAR based on sliding window data reception according to claim 1, characterized in that: Step one includes: The sliding window received data is sequentially subjected to distance Fourier transform, distance matched filtering, spectrum center shift, azimuth Fourier transform and transformed into wave number domain form; The expression of sliding window receiving two-dimensional time domain echo data is: Among them, s slide (t a ,t r ) is the sliding window receiving two-dimensional time domain echo, A slide (t a ,t r ) is the time domain envelope in sliding window mode, t r is the distance to speed time, t a is the azimuth time, f c is the carrier frequency, k r is the range modulation frequency, c is the speed of light, (-x0, -y0) is the reference coordinate of radar S, and there is a target P (x t ,y t ), R t is the instantaneous distance from the target P to the radar S, v is the radar speed, and θ is the oblique angle; Perform range Fourier transform and range matched filtering, and the echo expression obtained is: Among them, s slide (t a ,f r ) is the sliding window receiving distance, time domain, azimuth and frequency domain echo, f r is the distance frequency; After shifting the center of the spectrum and performing azimuth Fourier transform, the obtained two-dimensional wavenumber domain signal expression is: Among them, s slide (K x ,K r ) is the sliding window receiving two-dimensional wavenumber domain echo, K x , K r are defined as the wave numbers in azimuth and range directions respectively, and the expressions are: where f r is the distance frequency, f a is the azimuth frequency, K rc is the distance to the wave number center, and its value is 3. The wavenumber domain imaging processing method for high squint spotlight SAR based on sliding window data reception according to claim 2 is characterized in that: Step 2: Multiply the two-dimensional wavenumber domain echo by the reference function. The reference function is: Among them, R0 is the radar reference distance; the echo expression is: In the formula, s' slide (K x ,K r ) is the two-dimensional wavenumber domain echo signal after multiplying with the reference function.

4. The wavenumber domain imaging processing method for high squint spotlight SAR based on sliding window data reception according to claim 3 is characterized in that: Step 3: Use the two-dimensional fast separable interpolation method to decouple the two-dimensional coupling caused by the sliding window receiving mode. The interpolation direction selected is interpolation along the line of sight, specifically: Rotate the scene coordinate system, choose to interpolate along the line of sight, and transform the echo expression into: s' slide (K x ,K r )=exp[-jG y (K x ,K r )·y' t ]·exp[-jG x (K x ,K r )·x' t ], Among them, x′ t , y′ t are the position coordinates of the target point in the line of sight coordinate system, G x (K x ,K r ), G y (K x ,K r ) are the wavenumber transformation expressions in azimuth and distance, respectively; To perform two-dimensional decoupling of the signal, the following variable substitutions need to be completed: Solve the above equation in reverse and get: Among them, H x (K″ x ,K″ y ), H r (K″ x ,K″ y ) are K x , K r About K' x and K″ y The function expression of .

5. The wavenumber domain imaging processing method for high squint spotlight SAR based on sliding window data reception according to claim 4 is characterized in that: The echo multiplied by the reference function is interpolated in azimuth and range, denoted as Interp 1a2r ,Interp 1a2r Interpolation methods include: Through azimuth interpolation, the sampling points are made at K″ x -K r The coordinate system is evenly distributed, specifically: In K″ x -K r Coordinate system setting K″ x Uniformly distributed coordinate points, and then according to K″ x =G x (K x ,K r ) Inverse solution to obtain these points in K x -K r K of the mapping point of the coordinate system x The coordinate values ​​are: Among them, m x (K″ x ,K r ) is K x About K″ x and K r Function expression of ; After obtaining the coordinates of the mapping points in each row, the echo data values ​​of the mapping points are returned to K″ row by row through interpolation. x -K r Coordinate system, after all rows are interpolated, the echo sampling point is at K″ x -K r To achieve uniform distribution on the coordinate system, the echo expression becomes: s 11 '(K″ x ,K r )=exp(-jK″ x ·x″ t )·exp[-j·h y (K″ x ,K r )·y′ t ], Among them, s 11 '(K″ x ,K r ) is the two-dimensional wavenumber domain echo signal after azimuth interpolation, h y (K″ x ,K r ) is K″ y About K″ x -K r The expression of K r =H r (K″ x ,K″ y ) is inversely solved, specifically: Then, the sampling point is interpolated at K″ x -K″ y The coordinate system becomes a two-dimensional uniform distribution, specifically: In K″ x -K″ y The coordinate system is along each column K″ x Setting K″ y Uniformly distributed coordinate points, according to K″ x , K″ y With K r The relationship K r =H r (K″ x ,K″ y ) Calculate the coordinate point set at K″ x -K r Mapping point K in the coordinate system r After obtaining the coordinates of the mapping points in each column, the echo data of the mapping points are returned to K″ column by column through interpolation. x -K″ y Coordinate system, after all columns are interpolated, the echo sampling point is at K″ x -K″ y To achieve uniform distribution, the echo expression becomes: s' slide (K″ x ,K″ y )=exp(-jK″ y ·y′ t )·exp(-jK″ x ·x′ t ) Among them, s' slide (K″ x ,K″ y ) is the two-dimensional wavenumber domain echo signal after two-dimensional decoupling.

6. The wavenumber domain imaging processing method for high squint spotlight SAR based on sliding window data reception according to claim 4, characterized in that: The echo multiplied by the reference function is interpolated in range and azimuth, denoted as Interp 1r2a ,Interp 1r2a Interpolation methods include: Through distance interpolation, the sampling points are made in K x -K″ y The coordinate system is evenly distributed, specifically: In K x -K″ y Coordinate system setting K″ y Uniformly distributed coordinate points, and then according to K″ y =G y (K x ,K r ) Inverse solution to obtain these points in K x -K r K of the mapping point of the coordinate system r The coordinate values ​​are: Among them, m r (K x ,K″ y ) is K r About K x and K' y Function expression of ; After obtaining the coordinates of the mapping points in each column, the echo data of the mapping points are returned to K column by column through interpolation. x -K″ y Coordinate system, after all columns are interpolated, the echo sampling point is at K x -K″ y The coordinate system achieves uniform distribution, and the echo expression is: s 12 '(K x ,K″ y )=exp(-jK″ y ·y′ t )·exp[-j·h x (K x ,K″ y )·x′ t ], Among them, s 12 '(K x ,K″ y ) is the two-dimensional wavenumber domain echo signal after completing the distance interpolation, h x (K x ,K″ y ) is K″ x About K x -K′ y The expression of K x =H x (K″ x ,K″ y ) is inversely solved, specifically: Then, the sampling point is interpolated at K″ x -K″ y The coordinate system becomes a two-dimensional uniform distribution, specifically: In K″ x -K″ y The coordinate system is along each row K″ y Setting K″ x Uniformly distributed coordinate points, according to K″ x , K″ y With K x The relationship K x =H x (K″ x ,K″ y ) Calculate the coordinate point set in K x -K″ y The coordinates of the mapping points in the coordinate system. After obtaining the coordinates of the mapping points in each row, the echo data of the mapping points are returned to K″ row by row through interpolation. x -K″ y Coordinate system, after all rows are interpolated, the echo sampling point is at K″ x -K″ y The coordinate system achieves uniform distribution, and the echo expression becomes s' slide (K″ x ,K″ y ).

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