Synthetic Aperture Radar High Squint Imaging Method Based on Improved ω-k Algorithm

Abstract

The present invention provides a synthetic aperture radar high squint imaging method based on an improved ω‑k algorithm. In the present invention, first, in the high squint SAR imaging process, based on a preset squint SAR observation geometric model and a 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 implemented by multiplying a two-dimensional frequency reference function and Stolt interpolation, azimuth position correction is implemented in the azimuth frequency domain, and range position correction is implemented by reconstructing a 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 a SAR image with no position offset and high resolution is obtained.

Description

Technical Field

[0001] The present 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 a high-resolution active remote sensing sensor. It is a coherent detection radar. It utilizes synthetic aperture technology through the motion of the radar platform to achieve a large equivalent antenna aperture, thereby achieving high resolution in azimuth. It also achieves high resolution in range by transmitting a wide-bandwidth signal. Generally, SAR operating in the forward-looking side-view mode is sufficient for reconnaissance and mapping. However, if advance target detection is required, SAR should be operated in the forward-looking wide-angle mode.

[0003] In the traditional high squint wavenumber domain algorithm (ω-k Algorithm, referred to as the 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 range positioning under 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 taken into account in previous processing algorithms, which requires resampling the range frequency axis to satisfy the sampling distribution after mapping, otherwise it will cause a range position offset. This offset has little effect when looking straight sideways or when 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 high squint imaging to ensure the accuracy of range positioning. Summary of the Invention

[0004] (1) Technical problems solved

[0005] In response to the shortcomings of the existing technology, 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 angles and the influence of Stolt interpolation on range positioning under high squint angles.

[0006] (2) 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 and the azimuth position is corrected;

[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 geometric model includes:

[0017] In the given rectangular coordinate system O-xyz, the radar flies along the x direction, with a flight height of h and a speed of v. a , the radar slant 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.

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

[0019] (1) Constraints of the elevation beamwidth and slant angle on the elevation direction

[0020] The downward viewing angle is α and the oblique viewing angle is θ sUnder 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:

[0021]

[0022] 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 pitch angle pointing downward toward the center of the antenna beam, θ r is the antenna elevation beamwidth, cos is the cosine function, arcsin and sin are the inverse sine and sine functions respectively;

[0023] (2) Constraints of azimuth beamwidth and slant 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 carrier antenna beam front 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 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 x is the azimuth coordinate of the target area where the trailing edge of the carrier antenna beam ends observation. 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 illuminating the target area;

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

[0029]

[0030] Where arctan is the inverse tangent function.

[0031] Preferably, the reference function is exp(jφ ref (fa ,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 range 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.

[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 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, configured to sequentially perform Doppler center estimation and compensation on the original echo data;

[0048] a first transformation module, configured to perform a two-dimensional fast Fourier transform on the echo data after Doppler center compensation, so as to transform the data into a two-dimensional frequency domain;

[0049] a compression module configured to perform reference function multiplication on the two-dimensional frequency domain to fully focus the target point at the reference slant range to achieve consistency compression; and then perform Stolt interpolation to fully focus the target point at the non-reference slant range to achieve complementary compression;

[0050] The first correction module is used to compensate the overall offset along the direction position in 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 azimuth position correction to transform the data back into the two-dimensional time domain;

[0052] The second correction module is used to correct the range position of the two-dimensional time domain by reconstructing the range sampling grid method 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 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, the programs including instructions for executing the synthetic aperture radar high squint imaging method as described above.

[0056] (3) 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 existing technology, it has the following advantages:

[0058] In the present invention, first, during the high squint SAR imaging process, effective raw echo data of the target scene area is obtained based on a preset squint SAR observation geometry model and a quantitative constraint relationship between radar operating parameters. Then, Doppler center estimation and compensation, consistent compression, complementary compression, azimuth position correction, and range position correction are sequentially performed, wherein consistent compression and complementary compression are respectively implemented by multiplying a two-dimensional frequency reference function 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. In response to 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 achieve two-dimensional position correction, and ultimately obtain a high-resolution SAR image with no position offset. 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 following briefly introduces the drawings required for use in the embodiments or the description of the prior art. 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 any creative work.

[0060] Figure 1 A 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 2A 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 scenario provided by an embodiment of the present invention;

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

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

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

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

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

[0071] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention are clearly and completely described. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0072] The embodiments of the present application provide 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 angles and the influence of Stolt interpolation on range positioning under high squint angles.

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

[0074] The applicants recognized that the traditional high squint ω-k imaging algorithm does not consider the impact of high squint imaging on azimuth positioning and range positioning, including two aspects: the azimuth position offset caused by the high squint angle and the impact of Stolt interpolation on range positioning under the high squint angle.

[0075] Based on the acquisition of high squint data and the characteristics of the ω-k algorithm, the embodiments of the present invention analyze the causes of azimuth and range position offsets, provide analytical quantities that cause the offsets, adjust the ω-k algorithm process, and embed the two-dimensional range correction process into the imaging process, thereby achieving high-resolution imaging with no offset in high squint conditions.

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

[0077] Example 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 geometry 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 to correct the azimuth position;

[0084] S6. performing a two-dimensional inverse fast Fourier transform on the two-dimensional frequency domain after 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 geometry model and a quantitative constraint relationship between radar operating parameters, providing a reference for achieving effective information acquisition of the observation area under high squint conditions. On the other hand, a correction process is embedded into the imaging process of the ω-k algorithm to address the offset of the target azimuth position and range position caused by high squint, thereby achieving two-dimensional position correction and ultimately obtaining high-resolution SAR images without 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. Among them, consistent compression and complementary compression are respectively implemented by two-dimensional frequency reference phase multiplication and Stolt interpolation, azimuth position correction is implemented in the azimuth frequency domain, and range position correction is achieved by reconstructing the range sampling grid.

[0088] Next, we will combine Figure 2 The following steps are described in detail:

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

[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 rectangular coordinate system O-xyz, the radar flies along the x direction, with a flight height of h and a speed of v. a , the radar slant 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.

[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 during data acquisition.

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

[0094] (1) Constraints of the elevation beamwidth and slant angle on the elevation direction

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

[0096]

[0097] Where cos is the cosine function.

[0098] In the case of straight side view and strabismus, 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] Here, 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] In general, the platform flight altitude, oblique angle, and radar incident angle are limited to a certain range. Once the flight altitude h, θ s Oblique and downward perspectives The range of the radar beam can be covered in the pitch direction and the range of the radar beam can be determined, that is, the minimum value of αmin Pick The maximum value of α max Pick α c is the radar pitch angle pointing downward toward the center of the antenna beam, θ r is the antenna elevation beamwidth.

[0108] Formula (4) describes the range coordinate value observed at 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; It is monotonically decreasing on the interval, and arcsin(x) is monotonically increasing on the interval. According to the properties of the composite function, It is monotonically decreasing on the interval; at the same time, it is known that cos(x) is monotonically decreasing on the interval, so 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 , the cross-heading coordinate y0 of the beam center on the horizontal ground increases monotonically in the interval, and its boundary value is:

[0110]

[0111] Among them, y 0max 、y 0min are the maximum and minimum values of y0 respectively.

[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 viewing angle, the above constraints are used to design parameters such as the antenna downward viewing angle and range beam width to ensure effective acquisition of the target scene area.

[0113] (2) Constraints of azimuth beamwidth and slant angle on heading range

[0114] In general, the constraints on the observation scene are two-dimensional, and the main analysis focuses on the limitations of various parameters on the observation width in the range direction. To achieve complete coverage of the target scene area, the azimuth flight range also needs to be designed during actual data acquisition.

[0115] In the slant range plane, for a real or simulated scenario, such as Figure 4 As shown, in order to ensure that all points in the scene can be fully observed, 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:

[0116]

[0117] Among them, X s is the azimuth coordinate when the carrier antenna beam front first observes the target area, x p1 is the azimuth coordinate of the edge point P1 where the front edge of the carrier antenna beam first illuminates the target area, R sp1 The slant range coordinate of the edge point P1 where the front edge of the carrier antenna beam first illuminates the target area;

[0118] X e x is the azimuth coordinate of the target area where the trailing edge of the carrier antenna beam ends observation. p2 is the azimuth coordinate of the edge point P2 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 P2 when the trailing edge of the carrier antenna beam ends irradiating the target area.

[0119] It should be noted that, in addition to the above, Figure 4 The parameter symbol R in p1 The shortest slant distance from the front edge of the carrier antenna beam to the edge point P1 of the target area for the first time; X pm X is the azimuth coordinate of the aircraft when the center of the antenna beam passes through the target point P1; pe ΔX is the azimuth coordinate of the aircraft when the trailing edge of the antenna beam passes through the target point P1. At this time, the antenna beam completes the complete illumination process of the target P1; p1 The azimuth position of the target point P1 at the oblique angle θ s Add an additional lead offset; R p2 The shortest slant distance to the edge point P2 when the trailing edge of the carrier antenna beam ends irradiating the target area.

[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 a large squint, 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 5 As shown in the figure, 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 leading 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 condition 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 slant 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 geometry model and the radar operating parameters, this step specifically includes:

[0130] During a mission, large forward squint SAR technology is used to collect information about the area of interest. First, based on the constraints of the geographic location of the area to be observed (Equations (5), (6), and (9), the flight path is planned and the parameters such as the squint angle and incident angle of the radar system are selected to ensure optimal coverage and data acquisition, ensuring that the radar system can effectively capture the reflected signals in the target area. After completing 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 by 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 generally involves the following steps:

[0135] First, the raw echo data collected by the SAR system is digitized and preprocessed, including denoising and matched filtering. The Doppler frequency shift 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, n0 is the selected starting range gate index number, and N is the range gate length selected for azimuth spectrum estimation.

[0142] Finally, the 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, resulting in abnormal bulges at certain points. These will cause the peak extraction method to fail in obtaining the Doppler center. After fitting and smoothing, this abnormal effect will be greatly reduced, 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 remove phase distortion caused by Doppler frequency shift. Doppler center compensation is typically performed during SAR data preprocessing to ensure accurate input data for subsequent imaging. Based on the estimated Doppler center frequency, the phase of the echo signal is adjusted to compensate for the Doppler frequency shift. This typically involves signal resampling or phase adjustment.

[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, a two-dimensional Fourier transform (FFT) is performed on the data after Doppler center compensation 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 consistent compression:

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

[0152]

[0153] Among them, f r is the range frequency of the transmitted linear frequency modulation signal, and F r is the range sampling rate, 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.

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

[0155] Analyzing the squint signal characteristics in the slant range plane, the transmitted signal is a linear frequency modulation signal, and 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 beam center 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 of the strabismus are analyzed, and r(t a ) at t ac Perform Taylor expansion near

[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 quadratic migration, and the fourth term is the cubic migration. In the large squint mode, the target slant distance has a large linear movement.

[0161] Perform distance Fourier transform on equation (14) and 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 f0 is often much larger than the range frequency, that is, f0>>f r .

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

[0166]

[0167] Using the stationary phase principle, the phase expression is obtained as

[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 ,fr )} (20)

[0171] Construct the two-dimensional reference phase according to formula (20):

[0172]

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

[0174] On this basis, this step performs the following additional compression:

[0175] Consistent compression only completes the reference slope distance R ref It is fully focused at the reference slant distance, but not fully focused at the non-reference slant distance, and as the slant distance moves away from R ref , the defocus will become more and more serious. Here, Stolt interpolation in the two-dimensional frequency domain is used to compensate for the matching residual at the non-reference distance, thus achieving complete focusing at the non-reference distance.

[0176] In step S5, for the two-dimensional frequency domain after Stolt interpolation, the overall offset is compensated along the direction position 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, from the imaging geometry, we know 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 the azimuth position is added with an additional advance offset, such as Figure 6 shown.

[0181] The azimuth advance offset is the azimuth offset at different slant ranges. This means that the offset has a range-variable property. After Stolt, the offsets of each range gate are corrected to the reference range. The offset ΔX = R ref tan(θ s ), which is an overall offset. The offsets on all range gates are equal. This offset can be uniformly removed during imaging processing to ensure accurate azimuth position correction. The correction process is performed 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 azimuth compression. The correction process can be implemented using Equation (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 formula (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 azimuth position correction to transform the data 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. There are two interpolation 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, which 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, we can see that the equivalent sampling rate after mapping is F rnew , f rdd Frequency range is forced to be allocated 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 the equivalent sampling rate F after mapping 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 close to R 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 distributed 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 will f rdd Limited 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 dimension 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 range is not affected, only the frequency interval is changed. 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 formula (26).

[0201] Thus, the embodiment of the present invention completes 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 simulations were carried out. First, a point target performance analysis method was given:

[0203] The purpose of point target performance analysis is to comprehensively evaluate and understand the capabilities of high squint SAR imaging in actual imaging processes, 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, the following are specifically included:

[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, then 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 range and azimuth directions of the intercepted unrotated image are N r and N a , then the coordinates of the range and azimuth directions 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) Homogenize 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 based on 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. Coordinate 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. Based on the two-dimensional coordinate distribution of R' and x' before interpolation and the target image, interpolate the image values at R' and x'. You can use the Matlab built-in function griddata.

[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 Numerical Radar operating frequency 1.6GHz Radar effective speed 150m / s PRF 68Hz bandwidth 50MHz Squint angle 30°

[0228] The target point distribution of the simulation scene is 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 Figure 9 The 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 the simulated results with the set point target positions, we found that they were generally consistent with the set results. Statistical analysis showed a standard deviation of 1.1m for azimuth and 0.24m for range. There was a slight discrepancy between the imaged positions and the actual set positions, primarily due to factors such as the system's resolution.

[0235] The image after imaging is analyzed. First, the point target is extracted. Then, the point target performance analysis method is used to rotate and interpolate the point target. The point targets before and after rotation are as follows: Figures 10-11 As shown, slicing the rotated point target shows the following: Azimuth Peak Sidelobe Ratio / dB: -13.3463, Azimuth Integrated Sidelobe Ratio / dB: -11.1994, Azimuth Resolution / m: 2.4976, which are consistent with the theoretical values. Range Peak Sidelobe Ratio / dB: -13.3762, Range Integrated Sidelobe Ratio / dB: -11.2343, Range Resolution / m: 2.7973, which are also consistent with the theoretical values.

[0236] Example 2:

[0237] An 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, configured to sequentially perform Doppler center estimation and compensation on the original echo data;

[0240] a first transformation module, configured to perform a two-dimensional fast Fourier transform on the echo data after Doppler center compensation, so as to transform the data into a two-dimensional frequency domain;

[0241] a compression module configured to perform reference function multiplication on the two-dimensional frequency domain to fully focus the target point at the reference slant range to achieve consistency compression; and then perform Stolt interpolation to fully focus the target point at the non-reference slant range to achieve complementary compression;

[0242] The first correction module is used to compensate the overall offset along the direction position in 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 azimuth position correction to transform the data back into the two-dimensional time domain;

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

[0245] Example 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] Example 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, the programs including a method for executing the synthetic aperture radar high squint imaging method as described in Example 1.

[0250] It is understandable 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 explanation, 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 existing technology, the present invention has the following beneficial effects:

[0252] To ensure that basic SAR observation requirements are met during high-squint SAR imaging, the present invention provides quantitative constraints between operating parameters such as the observation scene range, squint angle, incidence angle, and beamwidth. This provides a reference for effectively acquiring information about the observation area under high-squint conditions. To address the significant offsets in target azimuth and range caused by high squint, the present invention provides analytical measures for these offsets and embeds a compensation process into the ω-k imaging algorithm to achieve two-dimensional position correction, resulting in offset-free, high-resolution SAR images.

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

[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 they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. 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 various 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 complementary compression; For the two-dimensional frequency domain after Stolt interpolation, the overall offset is compensated along the direction position and the azimuth position is corrected; 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, wherein: The squint SAR observation geometric model includes: In the given rectangular coordinate system O-xyz, the radar flies along the x direction, with a flight height of h and a speed of v. a , the radar slant 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, wherein: The quantitative constraint relationships between the radar operating parameters include: (1) Constraints of the elevation beamwidth and slant 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 pitch angle pointing downward toward the center of the antenna beam, θ r is the antenna elevation beamwidth, cos is the cosine function, arcsin and sin are the inverse sine and sine functions respectively; (2) Constraints of azimuth beamwidth and slant angle on heading range The beam width in azimuth is θ az , 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 carrier antenna beam front 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 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 illuminating the target area; (3) Constraints between squint angle, elevation beamwidth, and azimuth beamwidth Where arctan is the inverse tangent function.

4. The synthetic aperture radar high squint imaging method according to claim 3, wherein: 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 range 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, wherein: 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, wherein: 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, wherein: If the new distance frequency axis f in the Stolt interpolation process rdd The frequency coverage 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, configured to sequentially perform Doppler center estimation and compensation on the original echo data; a first transformation module, configured to perform a two-dimensional fast Fourier transform on the echo data after Doppler center compensation, so as to transform the data into a two-dimensional frequency domain; a compression module configured to perform reference function multiplication on the two-dimensional frequency domain to fully focus the target point at the reference slant range to achieve consistency compression; and then perform Stolt interpolation to fully focus the target point at the non-reference slant range to achieve complementary compression; The first correction module is used to compensate the overall offset along the direction position in 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 azimuth position correction to transform the data back into the two-dimensional time domain; The second correction module is used to correct the range position of the two-dimensional time domain by reconstructing the range sampling grid method to obtain a final two-dimensional focused image.

9. A storage medium, characterized in that: The computer 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 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 instructions for executing the synthetic aperture radar high squint imaging method according to any one of claims 1 to 7.

Images