Synthetic aperture radar large squint imaging method based on improved omega-k algorithm

Abstract

The invention provides a synthetic aperture radar large squint imaging method based on an improved omega-k algorithm. According to the method, effective original echo data of a target scene area are obtained based on a preset squint SAR observation geometric model and a quantitative constraint relation between radar working parameters in a high-squint SAR imaging process; doppler center estimation and compensation, consistent compression, complementary compression, azimuth direction position correction and range direction position correction are sequentially executed, consistent compression and complementary compression are achieved through two-dimensional frequency reference function multiplication and Stolt interpolation, and azimuth direction position correction is achieved in an azimuth frequency domain. Distance direction position correction is achieved by reconstructing a distance direction sampling grid. For the offset of the target azimuth position and the distance position caused by large squint, the correction process is embedded into the imaging process of the omega-k algorithm, the correction of the two-dimensional position is realized, and finally, the high-resolution SAR image without position offset is obtained.

Description

Technical Field

[0001] The invention relates to the technical field of radar signal processing, and in particular to a synthetic aperture radar high squint imaging method based on an improved ω-k algorithm. Background Art

[0002] Synthetic Aperture Radar (SAR) is an active remote sensing sensor with high resolution. It is a coherent detection radar. It uses synthetic aperture technology to achieve a large equivalent antenna aperture through the movement of the radar platform, thereby obtaining high resolution in azimuth. It transmits a wide bandwidth signal to achieve high resolution in the distance upward. In general, SAR working in the positive side-view mode can basically meet the needs of reconnaissance and mapping. If you need to detect the target in advance, SAR needs to work in the large forward oblique mode.

[0003] In the traditional high squint wavenumber domain algorithm (ω-k Algorithm, referred to as ω-k algorithm), the impact on positioning mainly includes two aspects, the azimuth position offset caused by the high squint angle and the impact of Stolt interpolation on the distance positioning under the high squint angle. In particular, when performing Stolt interpolation, the frequency range in the mapping domain changes relative to the effective frequency range of the original domain, that is, the equivalent sampling rate is different from the original sampling rate. This change was not considered in the previous processing algorithm, which requires the distance frequency axis to be resampled to meet the sampling distribution after mapping, otherwise it will cause the distance position offset. This offset has a small effect when the straight side view or the squint angle is small, but as the squint angle increases, this offset will become more and more serious. Therefore, this offset must be corrected during the high squint imaging process to ensure the accuracy of the distance positioning. Summary of the invention

[0004] 1. Technical issues to be solved

[0005] In view of the shortcomings of the prior art, the present invention provides a synthetic aperture radar high-squint imaging method based on an improved ω-k algorithm, which solves the technical problems of azimuth position offset caused by high squint angle and range positioning affected by Stolt interpolation under high squint angle.

[0006] (II) Technical solution

[0007] To achieve the above objectives, the present invention is implemented through the following technical solutions:

[0008] A synthetic aperture radar high squint imaging method based on an improved ω-k algorithm, comprising:

[0009] Based on the preset squint SAR observation geometry model and the quantitative constraint relationship between radar operating parameters, the original echo data of the target scene area is obtained;

[0010] performing Doppler center estimation and compensation on the original echo data in sequence;

[0011] Performing a two-dimensional fast Fourier transform on the Doppler center compensated echo data to transform the data into a two-dimensional frequency domain;

[0012] For the two-dimensional frequency domain, reference function multiplication is performed to fully focus the target point at the reference slant distance to complete consistency compression; then Stolt interpolation is performed to fully focus the target point at the non-reference slant distance to complete complementary compression;

[0013] For the two-dimensional frequency domain after Stolt interpolation, the overall offset is compensated along the direction position to correct the azimuth position;

[0014] Performing a two-dimensional inverse fast Fourier transform on the two-dimensional frequency domain after azimuth position correction to transform the data back into a two-dimensional time domain;

[0015] For the two-dimensional time domain, a range sampling grid reconstruction method is adopted to correct the range position and obtain the final two-dimensional focused image.

[0016] Preferably, the squint SAR observation geometry model includes:

[0017] In the given spatial rectangular coordinate system O-xyz, the radar flies along the x direction, the flight altitude is h, and the speed is v a , the radar oblique angle is θ s , that is, the center pointing angle of the antenna beam, its projection in the horizontal plane is β, and the azimuth beam width is θ az , R is the shortest slant range on any range gate in the beam coverage scene in the positive side view mode, α is the radar downward viewing angle on any range gate, P(x p ,y p ) is any target point in the target scene area, R sp is the oblique angle θ s The slant distance when the center of the lower beam passes through the target P, M is the intersection of the beam center and the horizontal plane of the ray when the lower viewing angle is α in the positive side view mode, D(x 0 ,y 0 ) is the intersection of the beam center and the horizontal plane in the squint mode.

[0018] Preferably, the quantitative constraint relationship between the radar operating parameters includes:

[0019] (1) Constraints of the elevation beam width and squinting angle on the elevation direction

[0020] The downward viewing angle is α and the oblique viewing angle is θ s Under the constraint of 0 It is monotonically increasing on the interval, and its boundary values ​​are:

[0021]

[0022] Among them, y 0max ,y 0min y 0 The maximum and minimum values ​​of tan are the tangent function, and the lower viewing angle is The minimum value of α min Pick The maximum value of α max Pick α c is the radar elevation angle pointing downward from the center of the antenna beam, θ r is the antenna elevation beam width, cos is the cosine function, arcsin and sin are the inverse sine and sine functions respectively;

[0023] (2) Constraints of azimuth beam width and squint angle on heading range

[0024] The beam width in azimuth is θ az , the oblique angle is θ s Under the constraints of , the azimuth observation area should at least meet the following requirements:

[0025]

[0026] Among them, X s is the azimuth coordinate when the front edge of the carrier antenna beam first observes the target area, x p1 is the azimuth coordinate of the edge point where the front edge of the carrier antenna beam first illuminates the target area, R sp1 It is the slant range coordinate of the edge point where the front edge of the carrier antenna beam first illuminates the target area;

[0027] X e is the azimuth coordinate of the target area where the trailing edge of the carrier antenna beam ends observation, x p2 is the azimuth coordinate of the edge point when the trailing edge of the carrier aircraft antenna beam ends irradiating the target area, R sp2 The slant range coordinate of the edge point where the trailing edge of the carrier antenna beam ends irradiating the target area;

[0028] (3) Constraints between squint angle, elevation beamwidth, and azimuth beamwidth

[0029]

[0030] Among them, arctan is the inverse tangent function.

[0031] Preferably, the reference function is exp(jφ ref (f a ,f r )), where exp is the exponential function with base e, j is the complex imaginary part, φ ref (f a ,f r ) is the two-dimensional reference phase, and

[0032]

[0033] Among them, the radar transmission signal is set to a linear frequency modulation signal, f a is the azimuth frequency of the transmitted linear frequency modulation signal, f r is the distance frequency of the transmitted linear frequency modulation signal, and F r is the range sampling rate, R ref is the reference slope distance, f 0 is the center frequency of the radar, and f 0 >>f r , c is the propagation speed of electromagnetic waves in space, K r is the modulation frequency of the transmitted linear frequency modulation signal.

[0034] Preferably, the overall offset is expressed as ΔX=R ref tan(θ s ), the correction process of the azimuth position is expressed as:

[0035] S Acor (f a ,f r )=S(f a ,f r )exp(j2πf a ΔX / v a )

[0036] Among them, S(f a ,f r ) is the two-dimensional frequency domain after Stolt interpolation, S Acor (f a ,f r ) is the two-dimensional frequency domain after azimuth position correction.

[0037] Preferably, if the new distance frequency axis f in the Stolt interpolation process rdd The frequency coverage is not affected, only the frequency interval is changed. During the distance position correction process, the distance upward scale is modified to:

[0038] r s '=R ref +Δr

[0039] Where Δr is the compression of the time domain image after Stolt interpolation relative to the reference slant range, and

[0040]

[0041] Among them, F r is the original range sampling rate, r s is the original distance upward scale, is the equivalent sampling rate after mapping, and n is the number of distance unit indices.

[0042] Preferably, if the new distance frequency axis f in the Stolt interpolation process rdd The frequency coverage range is changed. During the distance position correction process, the distance upward scale is modified to:

[0043]

[0044] in, is the corresponding shortest sampling slant distance, N r ' is the number of sampling points upward after reconstructing the coordinates, is the equivalent sampling rate after mapping, T p is the time width of transmitting linear frequency modulation signal.

[0045] A synthetic aperture radar high squint imaging system based on an improved ω-k algorithm, comprising:

[0046] An acquisition module is used to acquire the original echo data of the target scene area based on a preset squint SAR observation geometric model and a quantitative constraint relationship between radar operating parameters;

[0047] An estimation and compensation module, used for sequentially performing Doppler center estimation and compensation on the original echo data;

[0048] A first transformation module is used to perform a two-dimensional fast Fourier transform on the echo data after Doppler center compensation to transform the data into a two-dimensional frequency domain;

[0049] A compression module is used to perform reference function multiplication on the two-dimensional frequency domain to fully focus the target point at the reference slant distance to complete consistency compression; then perform Stolt interpolation to fully focus the target point at the non-reference slant distance to complete complementary compression;

[0050] The first correction module is used to compensate the overall offset along the direction of the two-dimensional frequency domain after Stolt interpolation and correct the azimuth position;

[0051] A second transformation module is used to perform a two-dimensional inverse fast Fourier transform on the two-dimensional frequency domain after the azimuth position correction to transform the data back to the two-dimensional time domain;

[0052] The second correction module is used to correct the range position by reconstructing the range sampling grid method for the two-dimensional time domain to obtain a final two-dimensional focused image.

[0053] A storage medium stores a computer program for synthetic aperture radar high squint imaging based on an improved ω-k algorithm, wherein the computer program enables a computer to execute the synthetic aperture radar high squint imaging method as described above.

[0054] An electronic device, comprising:

[0055] One or more processors; a memory; and one or more programs, wherein the one or more programs are stored in the memory and are configured to be executed by the one or more processors, and the programs include instructions for executing the synthetic aperture radar high squint imaging method as described above.

[0056] (III) Beneficial effects

[0057] The present invention provides a synthetic aperture radar high squint imaging method based on an improved ω-k algorithm. Compared with the prior art, the present invention has the following beneficial effects:

[0058] In the present invention, firstly, in the process of high squint SAR imaging, based on the preset squint SAR observation geometric model and the quantitative constraint relationship between radar operating parameters, effective original echo data of the target scene area is obtained. Then, Doppler center estimation and compensation, consistent compression, complementary compression, azimuth position correction and range position correction are performed in sequence, wherein consistent compression and complementary compression are respectively realized by multiplying a two-dimensional frequency reference function and Stolt interpolation, azimuth position correction is realized in the azimuth frequency domain, and range position correction is realized by reconstructing the range sampling grid. In view of the offset of the target azimuth position and range position caused by high squint, the correction process is embedded in the imaging process of the ω-k algorithm to realize the correction of the two-dimensional position, and finally obtain a SAR image with no position offset and high resolution. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0060] Figure 1A block diagram of a synthetic aperture radar high squint imaging method based on an improved ω-k algorithm provided in an embodiment of the present invention;

[0061] Figure 2 A complete flow chart of an improved ω-k algorithm provided by an embodiment of the present invention;

[0062] Figure 3 A schematic diagram of a squint SAR observation geometric model provided by an embodiment of the present invention;

[0063] Figure 4 A schematic diagram of an observation scene provided by an embodiment of the present invention;

[0064] Figure 5 A schematic diagram of a constraint relationship between a squint angle, an elevation beam width and an azimuth beam width provided in an embodiment of the present invention;

[0065] Figure 6 An azimuth advance offset provided in an embodiment of the present invention is shown;

[0066] Figure 7 A distance frequency distribution diagram provided by an embodiment of the present invention;

[0067] Figure 8 A simulation scene distribution diagram provided by an embodiment of the present invention;

[0068] Fig. 9 A schematic diagram of an imaging result provided by an embodiment of the present invention;

[0069] Fig.10 A schematic diagram of a point target before rotation provided by an embodiment of the present invention;

[0070] Fig.11 A schematic diagram of a point target after rotation provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0071] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are clearly and completely described. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0072] The embodiment of the present application provides a synthetic aperture radar high squint imaging method based on an improved ω-k algorithm, thereby solving the technical problems of azimuth position offset caused by high squint angle and range positioning affected by Stolt interpolation under high squint angle.

[0073] The technical solution in the embodiment of the present application is to solve the above technical problems, and the overall idea is as follows:

[0074] The applicant recognizes that: in the traditional high squint ω-k imaging algorithm, the influence of high squint imaging on azimuth positioning and distance positioning is not considered, including two aspects: the azimuth position offset caused by the high squint angle and the influence of Stolt interpolation on distance positioning under the high squint angle.

[0075] The embodiment of the present invention starts from the acquisition of high squint data and the characteristics of the ω-k algorithm, analyzes the causes of azimuth position offset and distance position offset, gives the analytical value of the offset, adjusts the ω-k algorithm process, and embeds the two-dimensional distance correction process into the imaging process, so as to achieve high-resolution imaging without offset in the case of high squint.

[0076] In order to better understand the above technical solution, the above technical solution will be described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0077] Embodiment 1:

[0078] like Figure 1 As shown, an embodiment of the present invention provides a synthetic aperture radar high squint imaging method based on an improved ω-k algorithm, comprising:

[0079] S1. Based on the preset squint SAR observation geometric model and the quantitative constraint relationship between radar operating parameters, the original echo data of the target scene area is obtained;

[0080] S2, performing Doppler center estimation and compensation on the original echo data in sequence;

[0081] S3, performing a two-dimensional fast Fourier transform on the echo data after Doppler center compensation to transform the data into a two-dimensional frequency domain;

[0082] S4, for the two-dimensional frequency domain, perform reference function multiplication to fully focus the target point at the reference slant distance to complete consistency compression; then perform Stolt interpolation to fully focus the target point at the non-reference slant distance to complete complementary compression;

[0083] S5, for the two-dimensional frequency domain after Stolt interpolation, the overall offset is compensated along the direction position, and the azimuth position is corrected;

[0084] S6, performing a two-dimensional inverse fast Fourier transform on the two-dimensional frequency domain after the azimuth position correction to transform the data back into the two-dimensional time domain;

[0085] S7. For the two-dimensional time domain, a range sampling grid reconstruction method is adopted to correct the range position and obtain a final two-dimensional focused image.

[0086] The embodiments of the present invention, on the one hand, introduce a preset squint SAR observation geometric model and a quantitative constraint relationship between radar operating parameters, which provides a reference for achieving effective information acquisition of the observation area under large squint conditions; on the other hand, in view of the offset of the target azimuth position and distance position caused by large squint, a correction process is embedded in the imaging process of the ω-k algorithm to achieve two-dimensional position correction, and finally obtain a high-resolution SAR image with no position offset.

[0087] like Figure 2 As shown, Figure 2 The complete process of the improved ω-k algorithm provided by an embodiment of the present invention is given, which mainly includes the acquisition of original echo data, Doppler center estimation and compensation, consistent compression, complementary compression, azimuth position correction and range position correction, etc., wherein consistent compression and complementary compression are respectively implemented by multiplication of two-dimensional frequency reference phase and Stolt interpolation, azimuth position correction is implemented in the azimuth frequency domain, and range position correction is implemented by reconstructing the range sampling grid.

[0088] Next, we will combine Figure 2 The following are the steps of the above solution:

[0089] In step S1, based on a preset squint SAR observation geometry model and a quantitative constraint relationship between radar operating parameters, original echo data of a target scene area is acquired.

[0090] like Figure 3 As shown, the preset squint SAR observation geometric model of the embodiment of the present invention includes:

[0091] In the given spatial rectangular coordinate system O-xyz, the radar flies along the x direction, the flight altitude is h, and the speed is v a , the radar oblique angle is θ s , that is, the center pointing angle of the antenna beam, its projection in the horizontal plane is β, and the azimuth beam width is θ az , R is the shortest slant range on any range gate in the beam coverage scene in the positive side view mode, α is the radar downward viewing angle on any range gate, P(x p ,y p ) is any target point in the target scene area, R sp is the oblique angle θ s The slant distance when the center of the lower beam passes through the target P, M is the intersection of the beam center and the horizontal plane of the ray when the lower viewing angle is α in the positive side view mode, D(x 0 ,y 0 ) is the intersection of the beam center and the horizontal plane in the squint mode.

[0092] In addition, in order to ensure the effective and complete acquisition of echo data in the observation area under large squint conditions, it is necessary to constrain the relationship between the squint angle, beam width, azimuth observation interval, etc., to provide guidance for route planning and parameter design for data acquisition.

[0093] Specifically, there are three types of two-dimensional constraints on the antenna beam:

[0094] (1) Constraints of the elevation beam width and squinting angle on the elevation direction

[0095] Depend on Figure 3 From the observation geometry in , we can see that the shortest slant distance and platform flight altitude under the positive side view condition satisfy:

[0096]

[0097] Among them, cos is the cosine function.

[0098] In the case of straight side view and oblique view, the distance between the beam center ray and the intersection point of the horizontal plane satisfies:

[0099]

[0100] Among them, tan is the tangent function and sin is the sine function.

[0101] According to equations (1) and (2), the oblique angle θ s The projection angle β in the horizontal plane is:

[0102]

[0103] Among them, arcsin is the inverse sine function.

[0104] According to the actual flight conditions and observation conditions, in the forward squint mode, θ and α are in the range On, and when satisfied When θ s <2α constraint.

[0105] According to the above geometric relationship, the downward viewing angle is α and the oblique viewing angle is θ s Under the constraint of , the cross-heading coordinates of the beam center on the horizontal ground are:

[0106]

[0107] Generally speaking, the platform flight altitude, oblique angle, and radar incident angle are limited to a certain range. Once the flight altitude h, θ are given, s Oblique and downward viewing angles The range of the radar beam can also be determined in terms of elevation, that is, the minimum value of αmin Pick The maximum value of α max Pick α c is the radar elevation angle pointing downward from the center of the antenna beam, θ r is the antenna elevation beamwidth.

[0108] Formula (4) describes the observed range coordinate value under a given platform flight altitude, oblique angle and radar down angle. In order to determine the range coordinate value of the radar working at the oblique angle θ s The observation range of the lower pitch upward, first, the monotonicity of equation (4) is analyzed. tan(α) is monotonically increasing in the interval; is monotonically decreasing on the interval, and arcsin(x) is monotonically increasing on the interval. From the properties of composite functions, we can see that It is monotonically decreasing on the interval; at the same time, it is known that cos(x) is monotonically decreasing on the interval, so is monotonically increasing on the interval.

[0109] In summary, the downward viewing angle is α and the oblique viewing angle is θ s Under the constraint of 0 It is monotonically increasing on the interval, and its boundary values ​​are:

[0110]

[0111] Among them, y 0max ,y 0min y 0 The maximum and minimum values ​​of .

[0112] It should be noted that when designing the radar system and planning the flight trajectory, in order to ensure complete coverage of the target scene area, given the observation scene and oblique angle, the above constraints are used to design parameters such as the antenna downward angle of view and range beam width to ensure effective acquisition of the target scene area.

[0113] (2) Constraints of azimuth beam width and squint angle on heading range

[0114] In general, the constraints on the observation scene are two-dimensional, and the main analysis is the restrictions of various parameters on the observation width in the distance. In order to achieve complete coverage of the target scene area, the flight range of the orientation also needs to be designed when obtaining actual data.

[0115] In the slant range plane, for a real or simulated scenario, such as Figure 4 As shown, to ensure that all points in the entire scene can be fully observed, the beam width in azimuth is θ az , the oblique angle is θ sUnder the constraints of , the azimuth observation area should at least meet the following requirements:

[0116]

[0117] Among them, X s is the azimuth coordinate when the front edge of the carrier antenna beam first observes the target area, x p1 The edge point P where the front edge of the carrier antenna beam first illuminates the target area 1 The azimuth coordinates, R sp1 The edge point P where the front edge of the carrier antenna beam first illuminates the target area 1 The slope range coordinates of

[0118] X e is the azimuth coordinate of the target area where the trailing edge of the carrier antenna beam ends observation, x p2 The edge point P is where the trailing edge of the carrier aircraft antenna beam ends irradiating the target area. 2 The azimuth coordinates, R sp2 The edge point P when the trailing edge of the carrier antenna beam ends irradiating the target area 2 The slope range coordinate.

[0119] It should be noted that in addition to the above, Figure 4 The parameter symbol R p1 The edge point P where the front edge of the carrier antenna beam first illuminates the target area 1 The shortest slope distance; X pm The center of the antenna beam passes through the target point P 1 The aircraft position coordinate at the time; X pe The trailing edge of the antenna beam passes through the target point P 1 The carrier azimuth coordinates at this time, when the antenna beam completes the target P 1 The complete irradiation process; ΔX p1 The target point P 1 The azimuth position is at the oblique angle θ s Add an additional lead offset to the bottom; R p2 The edge point P when the trailing edge of the carrier antenna beam ends irradiating the target area 2 The shortest slope distance.

[0120] (3) Constraints between squint angle, elevation beamwidth, and azimuth beamwidth

[0121] In order to ensure that the antenna can perform SAR imaging of the target even when working with large squint conditions, it is necessary to ensure that there is a change in Doppler frequency between the target and the radar, and that the target slant range can correspond one to one. The physical manifestation is that the antenna beam cannot cross the route.

[0122] like Figure 5As shown, the above constraint relationship is given, where γ is the projection of the antenna beam edge in the horizontal plane, point E is the intersection of the beam front ray and the horizontal plane, C is the intersection of the beam trailing ray and the horizontal plane, and E' is the intersection of the CE extension line and the x-axis.

[0123]

[0124] The constraint is to ensure that the area covered by the beam is on the heading side, that is,

[0125]

[0126] Combining equations (3), (7) and (8), we have

[0127]

[0128] In summary, when acquiring raw echo data, the parameters such as the squint angle, incident angle, and antenna azimuth beam width are selected to satisfy the constraints of equations (5), (6), and (9) to ensure effective and complete coverage of the target scene area.

[0129] After clarifying the specific contents of the quantitative constraint relationship between the squint SAR observation geometric model and the radar operating parameters, this step specifically includes:

[0130] During a mission, the large forward squint SAR technology is used to collect information about the area of ​​interest. First, according to the constraints of the geographical location of the area to be observed (Equations (5), (6), and (9), the route is planned and the parameters such as the squint angle and incident angle of the radar system are selected to ensure the best coverage and data acquisition, and to ensure that the radar system can effectively capture the reflected signal of the target area. After completing the mission planning, signal transmission and reception are the core links of SAR data acquisition.

[0131] In this step, the radar system transmits linear frequency modulation signals, which are reflected back after contacting the ground target and received by the radar system. The received signal contains key information such as the target's position and speed, which is crucial for subsequent data processing and analysis.

[0132] In step S2, Doppler center estimation and compensation are performed on the original echo data in sequence.

[0133] This step first performs Doppler center estimation:

[0134] The purpose of Doppler center estimation is to determine the center value of the Doppler frequency shift in the SAR system, that is, the center frequency of the Doppler spectrum. This parameter is crucial for subsequent Doppler compensation. Doppler center estimation usually involves the following steps:

[0135] First, the raw echo data collected by the SAR system is digitized and preprocessed, including denoising, matched filtering, etc. The Doppler frequency offset is estimated by analyzing the phase information and energy distribution of the echo signal. The raw data is converted to the range-Doppler domain:

[0136]

[0137] Among them, f a is the azimuth frequency of the transmitted linear frequency modulation signal, t a is the azimuth observation slow time, t r is the fast time observed in the distance direction, and j is the complex imaginary part.

[0138] The Doppler spectrum of the echo is modulated by the antenna pattern, including the Doppler center and the antenna shape.

[0139] Second, based on this principle, the Doppler spectra in multiple range gates are selected and smoothed to achieve a rough estimate of the antenna pattern.

[0140]

[0141] Where n is the range gate index number, n 0 is the selected starting range gate index number, and N is the range gate length selected for azimuth spectrum estimation.

[0142] Finally, the obtained antenna pattern is fitted using a Gaussian function or sinc(x). This is because the antenna pattern extracted from the echo may be affected by noise, producing abnormal protrusions at certain points. These will cause the failure of obtaining the Doppler center using the peak extraction method. After fitting and smoothing, this abnormal effect will be greatly weakened, improving the robustness of the method. After fitting, the antenna pattern is S m (f a ). By searching for the peak value, the corresponding frequency f is obtained. ac , which is the Doppler center.

[0143] On this basis, this step performs Doppler center compensation:

[0144] Based on the estimated Doppler parameters, the echo data is compensated to eliminate the phase distortion caused by the Doppler frequency shift. Doppler center compensation is usually completed in the SAR data preprocessing stage to ensure that the input data for subsequent imaging processing is accurate. Based on the estimated Doppler center frequency, the phase of the echo signal is adjusted to compensate for the Doppler frequency shift. This usually involves resampling or phase adjustment of the signal.

[0145] s rdac (t a ,t r )=s r (t a,t r )exp(-j2πf ac t a ) (12)

[0146] Among them, s rdac (t a ,t r ) is the echo signal after compensating the azimuth Doppler center, and exp is an exponential function with e as the base.

[0147] In step S3, a two-dimensional fast Fourier transform is performed on the echo data after Doppler center compensation to transform the data into a two-dimensional frequency domain.

[0148] In this step, the data after Doppler center compensation is subjected to a two-dimensional Fourier transform (FFT for short) to transform the data into a two-dimensional frequency domain (converting the time domain into the frequency domain).

[0149] In step S4, for the two-dimensional frequency domain, reference function multiplication is performed to fully focus the target point at the reference slant distance to complete consistency compression; then Stolt interpolation is performed to fully focus the target point at the non-reference slant distance to complete complementary compression.

[0150] This step first performs consistency compression:

[0151] By comparing with the reference function exp(jφ ref (f a ,f r )) to achieve the reference slope distance R ref The exact match and complete focusing at the location complete the consistent compression process. ref (f a ,f r ) is the two-dimensional reference phase, and

[0152]

[0153] Among them, f r is the distance frequency of the transmitted linear frequency modulation signal, and F r is the range sampling rate, f 0 is the center frequency of the radar, and f 0 >>f r , c is the propagation speed of electromagnetic waves in space, K r is the modulation frequency of the transmitted linear frequency modulation signal.

[0154] It should be noted that formula (13) is obtained based on signal feature analysis, specifically including:

[0155] Analyze the squint signal characteristics in the slant range plane. The transmitted signal is a linear frequency modulation signal. The received signal model is as follows:

[0156]

[0157] Among them, w r is the distance envelope, w a is the azimuthal envelope, is the time when the center of the beam passes through the target P, R sp is the oblique angle θ s The slant range when the center of the lower beam passes through the target P.

[0158] Firstly, the slant distance characteristics under the condition of strabismus are analyzed, and r(t a ) at t ac Taylor expansion is performed around

[0159]

[0160] The first term in equation (16) is the slant distance when the beam center passes through the target point, the second term is the linear movement, the third term is the secondary migration, and the fourth term is the tertiary migration. In the large squint mode, the target slant distance has a large linear movement.

[0161] Perform distance Fourier transform on equation (14) and we get

[0162]

[0163] in, It is the range spectrum envelope. The second phase term is unnecessary for range focusing and needs to be removed by building a matched filter in range compression.

[0164] It should be noted that the distance sampling rate must satisfy the sampling theorem, then F r is the range sampling rate. In addition, the radar carrier frequency f 0 is often much larger than the distance frequency, i.e. f 0 >>f r .

[0165] Perform azimuth Fourier transform on equation (17) to obtain

[0166]

[0167] Using the stationary phase principle, the phase expression is:

[0168]

[0169] Substituting equation (19) into equation (18), we get the two-dimensional spectrum of the echo data:

[0170] S r (f a ,f r )=W r (f r )W a (f a -f ac )exp{jφ a (f a ,f r )} (20)

[0171] According to formula (20), the two-dimensional reference phase is constructed:

[0172]

[0173] Where, the reference slope distance R ref The slant distance is usually chosen to be the center of the imaged scene.

[0174] On this basis, this step performs supplementary compression:

[0175] Consistent compression only completes the reference slope distance R ref Fully focused at the reference slope distance, not fully focused at non-reference slope distances, and as the slope distance moves away from R ref , the defocus will become more and more serious. Here, the matching residual at the non-reference distance is compensated by Stolt interpolation in the two-dimensional frequency domain, and the full focusing at the non-reference distance is achieved.

[0176] In step S5, for the two-dimensional frequency domain after Stolt interpolation, the overall offset is compensated along the direction to correct the azimuth position.

[0177] In this step, the oblique angle is θ relative to the front side view. s The azimuth position at the time of the additional offset ΔX P =R sp sin(θ s )=Rtan(θ s ), the azimuth offset at different slant ranges varies, indicating that the offset has range-variability. After Stolt, the offsets of each range gate are corrected to the reference distance, and the offset is

[0178] ΔX=R ref tan(θ s ) (twenty two)

[0179] This is the overall offset, and the offsets on all range gates are equal. This offset can be uniformly removed during imaging processing to ensure that the accurate azimuth position is accurately corrected.

[0180] Specifically, it can be known from the imaging geometry that for a target located at the slant distance R of the positive side view, the slant angle θ is s In this case, the moment when the beam center passes through the target has a certain advance, and an additional advance offset is added to the azimuth position, such as Figure 6 shown.

[0181] The azimuth advance offset is the azimuth offset at different slant ranges, which is variable, indicating that this offset has a range-variable property. After Stolt, the offsets of each range gate are corrected to the reference distance, and the offset ΔX = R ref tan(θ s ), which is the overall offset. The offsets on all range gates are equal. This offset can be uniformly removed in the imaging process to ensure that the accurate azimuth position is accurately corrected. The correction process is implemented in the two-dimensional frequency domain after Stolt interpolation, that is, a linear phase is compensated along the azimuth direction and the correction is completed before the azimuth compression. The correction implementation process can be implemented by formula (23).

[0182] S Acor (f a ,f r )=S(f a ,f r )exp(j2πf a ΔX / v a ) (twenty three)

[0183] Among them, S(f a ,f r ) is the two-dimensional frequency domain after Stolt interpolation, S Acor (f a ,f r ) is the two-dimensional frequency domain after azimuth position correction.

[0184] That is, the correction process in this step is implemented in the two-dimensional frequency domain after Stolt interpolation, and a linear phase is compensated along the azimuth direction through equation (23), and the correction is completed before azimuth compression.

[0185] In step S6, a two-dimensional inverse fast Fourier transform is performed on the two-dimensional frequency domain after the azimuth position correction to transform the data back into the two-dimensional time domain.

[0186] In this step, a two-dimensional inverse Fourier transform (IFFT) is performed on the two-dimensional frequency domain after the azimuth position correction, and the data is transformed into the two-dimensional frequency domain (the frequency domain is converted back to the time domain).

[0187] In step S7, for the two-dimensional time domain, a range sampling grid reconstruction method is adopted to correct the range position and obtain a final two-dimensional focused image.

[0188] In the ω-k algorithm, interpolation is required in the two-dimensional frequency domain. Interpolation can be divided into two methods: one is to keep the number of frequency sampling points unchanged, but change the frequency interval; the other is to keep the frequency interval unchanged, but increase the number of frequency sampling points. In the first case, after interpolation, it is found that the image obtained will shift in the distance direction, and the phenomenon is manifested as R ref The overall effect is that the image is compressed.

[0189] The above reasons are: the new distance frequency axis f in the distance frequency domain Stolt interpolation process rdd From the setting, it can be seen that the equivalent sampling rate after mapping is F rnew , f rdd The frequency range is forced to N r points, with a frequency interval of F rnew / N r , and the original frequency interval is F r / N r , F r is the original distance sampling rate, and is usually mapped to the equivalent sampling rate F rnew Than the original sampling rate F r The frequency distribution is as follows Figure 7 As shown, the sampling interval in the frequency domain becomes larger, where the red curve is the frequency interval F rnew / N r The frequency distribution of F r / N r The frequency distribution of . It can be seen that the spectrum sampling interval is stretched, and the stretching factor is F rnew / F r , stretching in the frequency domain is equivalent to compressing the image in the time domain, which is consistent with the phenomenon that occurs.

[0190] Since the time domain image obtained after frequency domain interpolation is based on the reference slant range R ref The center is compressed, so the interpolated image is relatively ref The compression amount is

[0191]

[0192] Among them, F r is the original range sampling rate, r s is the original distance upward scale (i.e. the distance quantization value corresponding to the original distance sampling rate), is the equivalent sampling rate after mapping, and n is the number of distance unit indices.

[0193] Therefore, after the imaging is completed, the slant distance corresponding to the distance sampling point is allocated by the new sampling rate, that is, the distance upward scale is changed to

[0194] r s '=R ref +Δr (25)

[0195] The above interpolation process converts f rdd Limit to N r The frequency interval changes, which affects the upward positioning of the distance. Therefore, f rdd Make the modification, keep the frequency interval unchanged, where are the maximum and minimum values ​​of the distance frequency after Stolt mapping; interpolation is then performed, which causes the distance size of the interpolated image to change, but the resulting image is not compressed. The distance scale needs to be modified to

[0196]

[0197] in, is the corresponding shortest sampling slant distance, N r ' is the number of sampling points upward after reconstructing the coordinates.

[0198] In summary, the distance-to-position process in this step can be summarized as follows:

[0199] (1) If the new distance frequency axis f in the Stolt interpolation process rdd The frequency coverage is not affected, only the frequency interval changes. During the distance position correction process, the distance upward scale is modified with reference to formula (25).

[0200] (2) If the new distance frequency axis f in the Stolt interpolation process rdd This causes the frequency coverage range to change. During the distance position correction process, the distance upward scale is modified with reference to equation (26).

[0201] So far, the embodiment of the present invention has completed the entire process of the synthetic aperture radar high squint imaging method based on the improved ω-k algorithm, and ensures that the final acquired two-dimensional focused image is a high-resolution SAR image with no position offset.

[0202] Furthermore, in order to verify the effectiveness of the improved ω-k algorithm and analysis provided by the embodiment of the present invention, numerical simulation is carried out. First, a point target performance analysis method is given:

[0203] The purpose of point target performance analysis is to comprehensively evaluate and understand the capabilities of high squint SAR imaging in the actual imaging process, especially in terms of resolution, peak sidelobe ratio, integrated sidelobe ratio, positioning accuracy, etc. To verify the imaging quality and positioning performance of the algorithm, specifically:

[0204] 1) Extract the point target from the image;

[0205] 2) Perform 16-fold interpolation;

[0206] 3) Rotate the interpolated point target by an angle of θ s , the rotation process is as follows;

[0207] a) Calculate the range and azimuth sampling intervals after rotation. If the range and azimuth sampling intervals before rotation are ΔR and ΔA respectively, the calculation formulas for the range and azimuth sampling intervals ΔR' and ΔA' after rotation are:

[0208] ΔR'=ΔRcos(θ s ) (27)

[0209] ΔA'=ΔAcos(θ s ) (28)

[0210] b) Rotate the coordinate system and determine the coordinate range after rotation. If the sampling points of the intercepted unrotated image in the range and azimuth directions are N r and N a , then the coordinates of the range and azimuth before rotation can be expressed as:

[0211] R=[-floor(Nr / 2):floor(Nr / 2)]ΔR (29)

[0212] x=[-floor(N a / 2):floor(N a / 2)]ΔA (30)

[0213] Calculate the clockwise rotation θ s The corresponding two-dimensional coordinate systems are:

[0214]

[0215] Calculate the distribution range of the two-dimensional coordinate system after the coordinate rotation, that is, x'∈[x' min ,x' max ],x'∈[x' min ,x' max ]R'∈[R' min ,R' max ].

[0216] c) Perform homogenization on the rotated coordinates. The sampling dimensions of the matrix composed of discrete coordinates are uniformly sampled before rotation. After rotation, the corresponding coordinate points may no longer be uniformly spaced. Therefore, coordinate homogenization and image data interpolation need to be performed based on the coordinate distribution after rotation.

[0217] i. Calculate the required sampling points according to the sampling interval and coordinate range after coordinate rotation;

[0218] N r '=floor((R' max -R' min ) / ΔR') (32)

[0219] N a '=floor((x' max -x' min ) / ΔA') (33)

[0220] ii. Coordinates are reset;

[0221] R" = [-floor(N' r / 2):floor(N′ r / 2)]ΔR' (34)

[0222] x"=[-floor(N' a / 2):floor(N' a / 2)]ΔA' (35)

[0223] d) Image data interpolation. According to the two-dimensional coordinate distribution of R' and x' before interpolation and the target image, the image values ​​at R' and x' are interpolated. The built-in function griddata in Matlab can be used.

[0224] 4) Perform slice analysis on the rotated image in azimuth and range directions to obtain indicators such as resolution, peak sidelobe ratio and integrated sidelobe ratio.

[0225] Next, the simulation parameters are given as shown in Table 1:

[0226] Table 1

[0227] parameter Numeric Radar operating frequency 1.6GHz Radar effective speed 150m / s PRF 68Hz bandwidth 50MHz Oblique angle 30°

[0228] The target points of the simulation scene are distributed as follows: Figure 8 The numerical results are shown in Table 2:

[0229] Table 2

[0230] P1 P2 P3 P4 P5 P6 P7 P8 P9 Range / m 3549 4242.6 4459.8 4036.1 4242.6 4459.8 4036.1 4242.61 4459.8 Azimuth / m 600 300 300 0 0 0 -300 -300 -600

[0231] The target position after imaging positioning is as follows Fig. 9The numerical results are shown in Table 3:

[0232] Table 3

[0233] P1 P2 P3 P4 P5 P6 P7 P8 P9 Range / m 3549 4243 4460 4036 4243 4460 4036 4243 4460 Azimuth / m 601 298.8 298.8 -1.1 1.1 1.1 -301 -298.8 -601

[0234] By comparing with the set point target position, it can be found that the simulation results obtained by the algorithm are basically consistent with the set ones. The standard deviation of the azimuth position is 1.1m, and the standard deviation of the distance position is 0.24m. There is a certain difference between the position obtained by imaging and the actual set position, which is mainly caused by the resolution of the system.

[0235] The image after imaging is analyzed. First, the point target is extracted. Then, the point target is rotated and interpolated using the above point target performance analysis method. The point targets before and after rotation are as follows: Figures 10-11 As shown, the point target after rotation is sliced: Azimuth peak sidelobe ratio / dB: -13.3463 Azimuth integral sidelobe ratio / dB: -11.1994 Azimuth resolution / m: 2.4976, which is consistent with the theoretical value. Range peak sidelobe ratio / dB: -13.3762 Range integral sidelobe ratio / dB: -11.2343 Range resolution / m: 2.7973, which is consistent with the theoretical value.

[0236] Embodiment 2:

[0237] The embodiment of the present invention provides a synthetic aperture radar high squint imaging system based on an improved ω-k algorithm, comprising:

[0238] An acquisition module is used to acquire the original echo data of the target scene area based on a preset squint SAR observation geometric model and a quantitative constraint relationship between radar operating parameters;

[0239] An estimation and compensation module, used for sequentially performing Doppler center estimation and compensation on the original echo data;

[0240] A first transformation module is used to perform a two-dimensional fast Fourier transform on the echo data after Doppler center compensation to transform the data into a two-dimensional frequency domain;

[0241] A compression module is used to perform reference function multiplication on the two-dimensional frequency domain to fully focus the target point at the reference slant distance to complete consistency compression; then perform Stolt interpolation to fully focus the target point at the non-reference slant distance to complete complementary compression;

[0242] The first correction module is used to compensate the overall offset along the direction of the two-dimensional frequency domain after Stolt interpolation and correct the azimuth position;

[0243] A second transformation module is used to perform a two-dimensional inverse fast Fourier transform on the two-dimensional frequency domain after the azimuth position correction to transform the data back to the two-dimensional time domain;

[0244] The second correction module is used to correct the range position by reconstructing the range sampling grid method for the two-dimensional time domain to obtain a final two-dimensional focused image.

[0245] Embodiment 3:

[0246] An embodiment of the present invention provides a storage medium storing a computer program for synthetic aperture radar high squint imaging based on an improved ω-k algorithm, wherein the computer program enables a computer to execute the synthetic aperture radar high squint imaging method as described in Example 1.

[0247] Embodiment 4:

[0248] An embodiment of the present invention provides an electronic device, including:

[0249] One or more processors; a memory; and one or more programs, wherein the one or more programs are stored in the memory and are configured to be executed by the one or more processors, and the programs include a method for executing the synthetic aperture radar high squint imaging method as described in Example 1.

[0250] It can be understood that the synthetic aperture radar high squint imaging system, storage medium and electronic device based on the improved ω-k algorithm provided in the embodiments of the present invention correspond to the synthetic aperture radar high squint imaging method based on the improved ω-k algorithm provided in the embodiments of the present invention. The explanations, examples and beneficial effects of the relevant contents can refer to the corresponding parts in the synthetic aperture radar high squint imaging method, and will not be repeated here.

[0251] In summary, compared with the prior art, the present invention has the following beneficial effects:

[0252] In the high squint SAR imaging process, in order to ensure that the basic conditions of SAR observation are met, the embodiment of the present invention provides a quantitative constraint relationship between working parameters such as the observation scene range, squint angle, incident angle, and beam width, providing a reference for obtaining effective information on the observation area under high squint conditions. In view of the large offset of the target azimuth position and distance position caused by high squint, the analytical value of the offset is given, and the compensation process is embedded in the ω-k imaging algorithm process to achieve two-dimensional position correction and obtain a high-resolution SAR image with no position offset.

[0253] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0254] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A synthetic aperture radar high squint imaging method based on an improved ω-k algorithm, characterized in that: include: Based on the preset squint SAR observation geometry model and the quantitative constraint relationship between radar operating parameters, the original echo data of the target scene area is obtained; performing Doppler center estimation and compensation on the original echo data in sequence; Performing a two-dimensional fast Fourier transform on the Doppler center compensated echo data to transform the data into a two-dimensional frequency domain; For the two-dimensional frequency domain, reference function multiplication is performed to fully focus the target point at the reference slant distance to complete consistency compression; then Stolt interpolation is performed to fully focus the target point at the non-reference slant distance to complete complement compression; For the two-dimensional frequency domain after Stolt interpolation, the overall offset is compensated along the direction position to correct the azimuth position; Performing a two-dimensional inverse fast Fourier transform on the two-dimensional frequency domain after azimuth position correction to transform the data back into a two-dimensional time domain; For the two-dimensional time domain, a range sampling grid reconstruction method is adopted to correct the range position and obtain the final two-dimensional focused image.

2. The synthetic aperture radar high squint imaging method according to claim 1, characterized in that: The squint SAR observation geometric model includes: In the given spatial rectangular coordinate system O-xyz, the radar flies along the x direction, the flight altitude is h, and the speed is v a , the radar oblique angle is θ s , that is, the center pointing angle of the antenna beam, its projection in the horizontal plane is β, and the azimuth beam width is θ az , R is the shortest slant range on any range gate in the beam coverage scene in the positive side view mode, α is the radar downward viewing angle on any range gate, P(x p ,y p ) is any target point in the target scene area, R sp is the oblique angle θ s The slant distance when the lower beam center passes through the target P, M is the intersection of the beam center and the horizontal plane of the ray when the lower viewing angle is α in the positive side view mode, and D(x0, y0) is the intersection of the beam center and the horizontal plane in the oblique view mode.

3. The synthetic aperture radar high squint imaging method according to claim 2, characterized in that: The quantitative constraint relationship between the radar operating parameters includes: (1) Constraints of the elevation beam width and squinting angle on the elevation direction The downward viewing angle is α and the oblique viewing angle is θ s Under the constraint of , the cross-heading coordinate y0 of the beam center on the horizontal ground increases monotonically in the interval, and its boundary value is: Among them, y 0max ,y 0min are the maximum and minimum values ​​of y0 respectively, tan is the tangent function, and the lower viewing angle The minimum value of α min Pick The maximum value of α max Pick α c is the radar elevation angle pointing downward from the center of the antenna beam, θ r is the antenna elevation beam width, cos is the cosine function, arcsin and sin are the inverse sine and sine functions respectively; (2) Constraints of azimuth beam width and squint angle on heading range The beam width in azimuth is θ az , the oblique angle is θ s Under the constraints of , the azimuth observation area should at least meet the following requirements: Among them, X s is the azimuth coordinate when the front edge of the carrier antenna beam first observes the target area, x p1 is the azimuth coordinate of the edge point where the front edge of the carrier antenna beam first illuminates the target area, R sp1 It is the slant range coordinate of the edge point where the front edge of the carrier antenna beam first illuminates the target area; X e is the azimuth coordinate of the target area where the trailing edge of the carrier antenna beam ends observation, x p2 is the azimuth coordinate of the edge point when the trailing edge of the carrier aircraft antenna beam ends irradiating the target area, R sp2 The slant range coordinate of the edge point where the trailing edge of the carrier antenna beam ends irradiating the target area; (3) Constraints between squint angle, elevation beamwidth, and azimuth beamwidth Among them, arctan is the inverse tangent function.

4. The synthetic aperture radar high squint imaging method according to claim 3, characterized in that: The reference function is exp(jφ ref (f a ,f r )), where exp is the exponential function with base e, j is the complex imaginary part, φ ref (f a ,f r ) is the two-dimensional reference phase, and Among them, the radar transmission signal is set to a linear frequency modulation signal, f a is the azimuth frequency of the transmitted linear frequency modulation signal, f r is the distance frequency of the transmitted linear frequency modulation signal, and F r is the range sampling rate, R ref is the reference slant range, f0 is the center frequency of the radar, and f0>>f r , c is the propagation speed of electromagnetic waves in space, K r is the modulation frequency of the transmitted linear frequency modulation signal.

5. The synthetic aperture radar high squint imaging method according to claim 4, characterized in that: The overall offset is expressed as ΔX=R ref tan(θ s ), the correction process of the azimuth position is expressed as: S Acor (f a ,f r )=S(f a ,f r )exp(j2πf a ΔX / v a ) Among them, S(f a ,f r ) is the two-dimensional frequency domain after Stolt interpolation, S Acor (f a ,f r ) is the two-dimensional frequency domain after azimuth position correction.

6. The synthetic aperture radar high squint imaging method according to claim 4, characterized in that: If the new distance frequency axis f in the Stolt interpolation process rdd The frequency coverage is not affected, only the frequency interval is changed. During the distance position correction process, the distance upward scale is modified to: r s '=R ref +Δr Where Δr is the compression of the time domain image after Stolt interpolation relative to the reference slant range, and Among them, F r is the original range sampling rate, r s is the original distance upward scale, is the equivalent sampling rate after mapping, and n is the number of distance unit indices.

7. The synthetic aperture radar high squint imaging method according to claim 4, characterized in that: If the new distance frequency axis f in the Stolt interpolation process rdd The frequency coverage range is changed. During the distance position correction process, the distance upward scale is modified to: in, is the corresponding shortest sampling slant distance, N r ' is the number of sampling points upward after reconstructing the coordinates, is the equivalent sampling rate after mapping, T p is the time width of transmitting linear frequency modulation signal.

8. A synthetic aperture radar high squint imaging system based on an improved ω-k algorithm, characterized in that: include: An acquisition module is used to acquire the original echo data of the target scene area based on a preset squint SAR observation geometric model and a quantitative constraint relationship between radar operating parameters; An estimation and compensation module, used for sequentially performing Doppler center estimation and compensation on the original echo data; A first transformation module is used to perform a two-dimensional fast Fourier transform on the echo data after Doppler center compensation to transform the data into a two-dimensional frequency domain; A compression module is used to perform reference function multiplication on the two-dimensional frequency domain to fully focus the target point at the reference slant distance to complete consistency compression; and then perform Stolt interpolation to fully focus the target point at the non-reference slant distance to complete complementary compression; The first correction module is used to compensate the overall offset along the direction of the two-dimensional frequency domain after Stolt interpolation and correct the azimuth position; A second transformation module is used to perform a two-dimensional inverse fast Fourier transform on the two-dimensional frequency domain after the azimuth position correction to transform the data back to the two-dimensional time domain; The second correction module is used to correct the range position by reconstructing the range sampling grid method for the two-dimensional time domain to obtain a final two-dimensional focused image.

9. A storage medium, characterized in that: The computer program for synthetic aperture radar high squint imaging based on the improved ω-k algorithm is stored, wherein the computer program enables the computer to execute the synthetic aperture radar high squint imaging method according to any one of claims 1 to 7.

10. An electronic device, characterized in that: include: one or more processors; Memory; and one or more programs, wherein the one or more programs are stored in the memory and are configured to be executed by the one or more processors, the programs including a program for executing the synthetic aperture radar high squint imaging method according to any one of claims 1 to 7.

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