Synthetic aperture radar imaging method and device for spiral track gliding aircraft

Abstract

The invention discloses a synthetic aperture radar imaging method and device for a spiral track gliding aircraft. The method comprises the following steps: sequentially carrying out time domain and frequency domain compensation processing on an echo signal through a time domain compensation function and a frequency domain compensation function to obtain a two-dimensional frequency domain signal; wherein the time domain compensation function and the frequency domain compensation function are constructed according to the relation between the high-precision instantaneous slope distance of any point in the imaging scene and the instantaneous slope distance of the reference point, and the instantaneous slope distance is determined based on a spiral trajectory geometric model with fast acceleration and speed change; and performing non-uniform fast Fourier transform on the two-dimensional frequency domain signal to obtain a transformed two-dimensional frequency domain signal. The imaging precision can be improved.

Description

Technical Field

[0001] The invention belongs to the technical field of signal processing, and in particular relates to a spiral trajectory gliding aircraft synthetic aperture radar imaging method and device. Background Art

[0002] Synthetic Aperture Radar (SAR) imaging technology can achieve air-to-ground imaging of objects, terrain and oceans without being constrained by time, natural climate conditions or distance. In the past few decades, people have conducted extensive research on conventional SAR installed on airborne or satellite platforms at a certain altitude and found that it is very effective in bad weather or lighting conditions. Advanced SAR imaging technology is constantly developing rapidly. Unlike traditional SAR, glider curved SAR operates at an altitude of 20 km to 100 km and can exceed Mach 5 to fill the gap between airborne and satellite SAR. Glider curved SAR can provide a larger weather observation area than aircraft and greater flexibility than satellites. Compared with traditional SAR, it has the characteristics of high survival rate, fast response time and wide detection range. It can achieve in-depth detection of sensitive areas, all-weather environmental monitoring, positioning of important targets, etc., and plays a very important role in the field of disaster monitoring and assessment. Glider spiral trajectory SAR is a special curved trajectory SAR imaging with stronger survivability and reconnaissance capabilities, showing great development and application prospects.

[0003] The current curved trajectory SAR squint imaging method based on the slant range model starts from the motion characteristics of the curved motion trajectory platform and performs a high-order approximation of its motion equation to derive the analytical solution of the two-dimensional spectrum. This method ensures the simplicity of the spectrum and has high accuracy, and can achieve full-aperture high-resolution imaging.

[0004] However, this method still has some shortcomings. In the spiral trajectory SAR imaging of gliding aircraft, since the speed and acceleration of the aircraft in all directions are not constant, the current slant range model does not accurately express the slant range under its spiral motion trajectory; therefore, the compensation function constructed by the current slant range model has a poor compensation effect when performing spiral trajectory SAR imaging of gliding aircraft, resulting in poor SAR imaging quality. At the same time, the spiral trajectory of the gliding aircraft has a large speed and variable acceleration in direction, which causes serious phase coupling of the echo signal and large space-variant errors.

[0005] Therefore, the description accuracy of the slant range model in the current SAR squint imaging method for the spiral trajectory is still insufficient, and it cannot accurately compensate for the coupled space-variant error caused by the spiral trajectory motion, resulting in poor imaging effect. Summary of the invention

[0006] The embodiment of the present invention provides a spiral trajectory gliding aircraft synthetic aperture radar imaging method and device, which can solve the problem that the description accuracy of the slant range model for the spiral trajectory in the current SAR squint imaging method is still insufficient, and the coupled space-variant error caused by the spiral trajectory motion cannot be accurately compensated, resulting in poor imaging effect.

[0007] In a first aspect, an embodiment of the present invention provides a spiral trajectory gliding aircraft synthetic aperture radar imaging method, the method comprising:

[0008] The echo signal is compensated in the time domain and the frequency domain by using the time domain compensation function and the frequency domain compensation function to obtain a two-dimensional frequency domain signal;

[0009] The time domain compensation function and the frequency domain compensation function are constructed based on the relationship between the high-precision instantaneous slant distance of any point in the imaging scene and the instantaneous slant distance of the reference point. The instantaneous slant distance is determined based on the spiral trajectory geometric model with fast acceleration and velocity changes.

[0010] Performing non-uniform fast Fourier transform on the two-dimensional frequency domain signal to obtain a transformed two-dimensional frequency domain signal;

[0011] The transformed two-dimensional frequency domain signal is inversely Fourier transformed to obtain a focused image.

[0012] In a second aspect, an embodiment of the present invention provides a spiral trajectory gliding aircraft synthetic aperture radar imaging device, comprising:

[0013] The compensation module is used to perform compensation processing in the time domain and the frequency domain on the echo signal in sequence through the time domain compensation function and the frequency domain compensation function to obtain a two-dimensional frequency domain signal;

[0014] The time domain compensation function and the frequency domain compensation function are constructed based on the relationship between the high-precision instantaneous slant distance of any point in the imaging scene and the instantaneous slant distance of the reference point. The instantaneous slant distance is determined based on the spiral trajectory geometric model with fast acceleration and velocity changes.

[0015] The Fourier transform module is used to perform non-uniform fast Fourier transform on the two-dimensional frequency domain signal to obtain the transformed two-dimensional frequency domain signal; and perform inverse Fourier transform on the transformed two-dimensional frequency domain signal to obtain the focused image of the aircraft.

[0016] In a third aspect, an embodiment of the present invention provides an electronic device, comprising a processor and a memory, wherein the memory is used to store computer programs; the processor can be used to execute the computer program (instructions) stored in the memory to implement the method of the first aspect above.

[0017] Compared with the prior art, the embodiments of the present invention have the following beneficial effects: since the high-precision instantaneous slant data and instantaneous tilt data used in the present invention are constructed based on the spiral trajectory geometric model, the speed and acceleration changes of the aircraft moving in the spiral trajectory are fully taken into account; therefore, by constructing a compensation function through high-precision instantaneous slant distance and instantaneous tilt data and compensating the echo signal through this compensation function, the compensation effect of the compensation function can be improved, thereby improving the imaging quality of the spiral trajectory; removing the coupled space-variant error in the phase through non-uniform fast Fourier transform can also improve the quality and accuracy of imaging. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 A flowchart of a method for constructing a high-precision instantaneous slant range model provided by an embodiment of the present invention;

[0019] Figure 2 A top view of a spiral trajectory motion provided by an embodiment of the present invention;

[0020] Figure 3 A schematic diagram of a spiral trajectory motion provided by an embodiment of the present invention;

[0021] Figure 4 A schematic diagram of a process flow for implementing a synthetic aperture radar imaging method for a spiral trajectory gliding aircraft provided by an embodiment of the present invention;

[0022] Figure 5 A schematic diagram of the structure of a synthetic aperture radar imaging device for a spiral trajectory gliding aircraft provided by an embodiment of the present invention;

[0023] Figure 6 A schematic diagram of SAR imaging effect of a spiral trajectory gliding aircraft provided by an embodiment of the present invention;

[0024] Figure 7 A schematic diagram of the structure of an electronic device provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0025] The present invention is further described in detail below with reference to specific embodiments, but the embodiments of the present invention are not limited thereto.

[0026] Example 1

[0027] Figure 1 The flowchart of the implementation of a method for constructing a high-precision instantaneous slant range model provided by an embodiment of the present invention is shown. As an example but not a limitation, the slant range model construction method may include steps S101-S102, and each step is described below.

[0028] S101, constructing a spiral trajectory geometric model.

[0029] In one example, a spiral trajectory geometric model can be constructed through the acceleration, velocity, position model, etc. of the aircraft when it moves in a spiral trajectory to obtain the coordinates of the aircraft in a three-dimensional coordinate system.

[0030] Exemplarily, the position model of the aircraft may be expressed as:

[0031] θ=w×η

[0032] r s =r(θ)=Ae θcotΛ

[0033] Among them, r s is the polar diameter, θ is the polar angle of response, w is the angular velocity of rotation, η is the azimuth slow time, A is the integration constant, and Λ is the angle between the component of the velocity vector in the yaw plane and the polar diameter.

[0034] For example, see Figure 2 , the platform radar mounted on the aircraft will rotate counterclockwise around the rotation axis when the aircraft makes a spiral motion.

[0035] For example, the acceleration and velocity of the aircraft can be expressed as:

[0036]

[0037] V η =V0+a·η

[0038] V z =V η cos l sinυ

[0039] =V z0 +a z η

[0040] Where a is acceleration, D is drag, m is mass, g is gravity acceleration, l is track angle, V η is the instantaneous velocity, V0 is the initial velocity, V z Vertical speed, υ is the track deviation angle, V z0 Vertical initial velocity, a z is the vertical acceleration.

[0041] Exemplarily, the spiral trajectory geometric model obtained through the geometric relationship (i.e., the coordinates of the aircraft in the three-dimensional coordinate system) can be expressed as:

[0042]

[0043] Among them, z η 、x η ,y η are the three-dimensional coordinate values ​​of the aircraft, and H is the initial platform height.

[0044] S102, constructing a high-precision instantaneous slant range model according to the spiral trajectory geometric model.

[0045] In one possible implementation, the instantaneous slant range of a reference point in a radar imaging scene can be Taylor expanded based on a spiral trajectory geometry model to obtain the Taylor expansion coefficient of the instantaneous slant range of the reference point; the instantaneous slant range of any point A of the aircraft in the imaging scene is Taylor expanded based on the reference point, and then multiple fittings are performed to simplify the multi-dimensional Taylor coefficients of point A; the simplified instantaneous slant range of point A is reconstructed to obtain a high-precision instantaneous slant range model.

[0046] In one example, see Figure 3 , the instantaneous slant distance expression of the reference point C can be obtained according to the imaging geometry model, and then the instantaneous slant distance of the reference point can be obtained by taking the absolute value.

[0047] For example, the instantaneous slope distance of reference point C is C (η)| can satisfy the following formula:

[0048]

[0049] Exemplarily, the instantaneous slope distance expression of reference point C can be expressed as:

[0050] r C (η)=(x c -x η ,y c -y η ,z c -z η )=(x C ,y C ,z C )

[0051] Among them, r C (η) is the instantaneous vector when the platform radar reaches the reference point, x c ,y c 、z c are the coordinates of the reference point C, x η ,y η 、z η are the coordinates of the platform radar.

[0052] In one example, the high-order Taylor expansion of the instantaneous slant range of the reference point C can be expressed as:

[0053]

[0054] in, is the Taylor expansion coefficient of the instantaneous slope distance of the reference point C.

[0055] The coefficients satisfy:

[0056]

[0057]

[0058] Where w is the angular velocity of rotation.

[0059] In one example, see Figure 3 , the instantaneous slant range of any point A in the radar imaging scene can be obtained according to the geometric relationship between point A and reference point C. The Taylor expansion of point A and each Taylor expansion coefficient can be obtained by expanding the instantaneous slant range. The multidimensional Taylor expansion coefficient of the instantaneous slant range of point A can be obtained by Taylor expansion based on the reference point. The simplified expressions of the multidimensional Taylor expansion coefficients can be obtained by fitting the multidimensional Taylor expansion coefficients of the instantaneous slant range of point A respectively. The instantaneous slant range of point A can be reconstructed according to the simplified expression of the multidimensional Taylor expansion coefficient to obtain a high-precision instantaneous slant range model.

[0060] Exemplarily, the Taylor expansion of the instantaneous slope distance of point A can be expressed as:

[0061]

[0062] Among them, |r A (η)| is the instantaneous slope distance of point A, r A is the polar diameter of point A, is the Taylor expansion coefficient of the instantaneous slope distance of point A.

[0063] Exemplarily, the Taylor expansion of point A based on the reference point can be expressed as:

[0064]

[0065] Wherein, Ρ0(η), Ρ1(η), Ρ2(η), Ρ3(η), Ρ4(η) are the multidimensional Taylor expansion coefficients of the corresponding terms of point A. are the slant range dependent term and the Doppler center term respectively, These are cross-coupling terms.

[0066] Exemplarily, the simplified quartic expression of the slope range history (i.e., the expression after the multidimensional expansion coefficient is simplified) can be obtained by fitting the complex three-dimensional Taylor series through fourth-order parameters. The simplified quartic expression of the slope range history can be expressed as:

[0067]

[0068] Among them, ν n , g n , en 、m n They are the fitting coefficients of the multidimensional Taylor expansion coefficients of the 0th to 4th order terms of the instantaneous slope distance of point A.

[0069] Exemplarily, the high-precision instantaneous slant range model can be expressed as:

[0070]

[0071] in:

[0072]

[0073] After simplification, we can get:

[0074]

[0075] Among them, |r A ′(η)| is the high-precision slope distance of point A.

[0076] It can be seen that the high-precision slant range model can decouple the quadratic terms while meeting the imaging accuracy, and the high-order terms can also be avoided, which can simplify the subsequent processing flow. Therefore, simplifying the slant range history by multiple fitting and Taylor expansion methods can effectively improve the speed and accuracy of subsequent imaging and meet the high real-time requirements of the glider platform.

[0077] The spiral trajectory gliding aircraft synthetic aperture radar imaging method provided in the embodiment of the present invention can be applied to electronic devices such as mobile terminals, personal notebook computers, supercomputers, etc. The embodiment of the present invention does not impose any restrictions on the specific type of electronic devices.

[0078] Figure 4 The following is a schematic diagram of a process flow of implementing a spiral trajectory gliding aircraft synthetic aperture radar imaging method provided by an embodiment of the present invention. As an example but not a limitation, the spiral trajectory gliding aircraft synthetic aperture radar imaging method may include steps S401-S405, which may be applied to the above electronic device, and each step is described below.

[0079] In a possible implementation, the following steps S401-S403 can be used to perform compensation processing on the echo signal in the time domain and the frequency domain based on the time domain compensation function and the frequency domain compensation function respectively to obtain a two-dimensional frequency domain signal.

[0080] S401, performing time domain consistent compensation processing on the echo signal by using a time domain compensation function to obtain a time domain compensated signal.

[0081] Exemplarily, the time domain compensation function and the frequency domain compensation function may be constructed based on the relationship between the high-precision instantaneous slant range of any point A in the radar imaging scene and the instantaneous slant range of the reference point.

[0082] In one example, the received echo signal may be first subjected to range Fourier transform and range pulse compression processing to obtain a radar signal, and then the radar signal may be subjected to consistency compensation in the azimuth time domain and the range frequency domain based on a time domain compensation function to obtain a time domain compensated signal.

[0083] Exemplarily, the echo signal may satisfy the following formula:

[0084]

[0085] Among them, s0(t r ,η) is, κ0 is the scattering coefficient, ω r is the distance window function, ω a is the azimuth window function, j is the imaginary unit, f c is the carrier frequency, c is the speed of light, γ is the modulation frequency, t r For distance fast time.

[0086] Exemplarily, the radar signal may satisfy the following formula:

[0087]

[0088] Among them, s1(f r ,η) is the radar signal, f r is the distance frequency.

[0089] Exemplarily, the time domain compensation function may satisfy the following formula:

[0090]

[0091] Among them, H0(f r ,η) is the time domain compensation function.

[0092] Exemplarily, the time domain compensation signal may satisfy the following formula:

[0093]

[0094] Among them, s2(f r ,η) is the time domain compensation signal.

[0095] S402, obtaining a two-dimensional frequency domain signal of an echo according to the time domain compensation signal based on the stationary phase principle.

[0096] Exemplarily, the echo two-dimensional frequency domain signal may satisfy the following formula:

[0097]

[0098] Among them, s3(f r ,f η ) is the echo two-dimensional frequency domain signal, fτ =(f r +f c ) / c,f η is the azimuth frequency, ζ4=γ4,γ n are the Doppler parameters of the range history and are all space-varying.

[0099] For example, the 2nd, 3rd, and 4th order coefficients ζ n Taylor series expansion yields:

[0100]

[0101] in, τ n are the expansion coefficients of different terms.

[0102] Specifically, is also an expansion coefficient.

[0103] For example, by adjusting the coefficient ζ n The phase of the two-dimensional frequency domain signal of the echo obtained by expansion and sorting can satisfy the following formula:

[0104]

[0105] Among them, Φ f is the phase of the echo two-dimensional frequency domain signal. The first term of the phase expression is the reference term that needs to be removed through subsequent compensation, the second term is the distance term, and the third term is the azimuth term.

[0106] S403, performing consistency compensation on the echo two-dimensional frequency domain signal in the two-dimensional frequency domain by using a frequency domain compensation function to obtain a two-dimensional frequency domain signal.

[0107] In an example, the frequency domain compensation function may also be a time domain compensation function constructed according to the relationship between the high-precision instantaneous slant distance of point A and the instantaneous slant distance of the reference point.

[0108] Exemplarily, the frequency domain compensation function may satisfy the following formula:

[0109]

[0110] Among them, H1(f r ,f η ) is the frequency domain compensation function.

[0111] In one example, the two-dimensional frequency domain signal may satisfy the following formula:

[0112]

[0113] Among them, s4(fr ,f η ) is a two-dimensional frequency domain signal. Compared with the echo two-dimensional frequency domain signal, the reference item is removed from the two-dimensional frequency domain signal. The two-dimensional frequency domain signal can be focused and imaged at the reference point in the imaging scene, but due to the large coupling space variation therein, the edge point of the imaging has a poor focusing effect at this time. Therefore, step S404 is required to remove the remaining coupling space variation in the phase.

[0114] S404, performing non-uniform fast Fourier transform on the two-dimensional frequency domain signal to obtain a transformed two-dimensional frequency domain signal.

[0115] In one example, the coupled spatial variation in the two-dimensional frequency domain signal can be removed by non-uniform fast Fourier transform to obtain a transformed two-dimensional frequency domain signal.

[0116] Exemplarily, the process of non-uniform fast Fourier transform can be expressed as:

[0117]

[0118] Among them, s5(p,q) is the transformed two-dimensional frequency domain signal, s4(f r ,f η ) is a two-dimensional frequency domain signal, and the 0th expansion coefficient based on the reference point satisfies: The 1st expansion coefficient satisfies: The first frequency domain expansion coefficient satisfies: The second frequency domain expansion coefficient satisfies: M and N are the number of sampling points in the range frequency domain and the azimuth frequency domain, respectively. <M / 2,-N / 2￡q<N / 2。

[0119] Exemplarily, the simplified transformed two-dimensional frequency domain signal may satisfy the following formula:

[0120]

[0121] Among them, B(m,n) is the conversion signal of the two-dimensional frequency domain signal about m and n, Ψ m,n ,Λ m,n is two expansion factors.

[0122] S405, performing inverse Fourier transform on the transformed two-dimensional frequency domain signal to obtain a focused image.

[0123] In one example, a two-dimensional fast Fourier transform may be performed on the transformed two-dimensional frequency domain signal, and then SAR imaging may be performed to obtain a focused image of the aircraft.

[0124] Since the high-precision instantaneous slant range model provided by the present invention is constructed based on the spiral trajectory geometric model, the speed and acceleration changes of the aircraft moving in the spiral trajectory are fully considered; therefore, the compensation function is constructed by the high-precision instantaneous slant range of the aircraft and the echo signal is compensated by this compensation function, which can improve the compensation effect of the compensation function and thus improve the imaging quality of the spiral trajectory; the coupled space-variant error in the phase is removed by non-uniform fast Fourier transform, which can also improve the quality and accuracy of imaging. Furthermore, the high-precision instantaneous slant range model obtained by Taylor expansion and multiple fitting simplification is used to determine the high-precision instantaneous slant range of the object to be observed, which can reduce the amount of calculation and enhance real-time performance.

[0125] Figure 5 The structure diagram of a spiral trajectory gliding aircraft synthetic aperture radar imaging device provided by an embodiment of the present invention is shown. As an example but not a limitation, the device 500 may include a compensation module 510 and a Fourier transform module 520.

[0126] The compensation module 510 is used to perform compensation processing in the time domain and the frequency domain on the echo signal in sequence through the time domain compensation function and the frequency domain compensation function to obtain a two-dimensional frequency domain signal;

[0127] The time domain compensation function and the frequency domain compensation function are constructed based on the relationship between the high-precision instantaneous slant distance of any point in the imaging scene and the instantaneous slant distance of the reference point. The instantaneous slant distance is determined based on the spiral trajectory geometric model with fast acceleration and velocity changes.

[0128] The Fourier transform module 520 is used to perform non-uniform fast Fourier transform on the two-dimensional frequency domain signal to obtain a transformed two-dimensional frequency domain signal; and perform inverse Fourier transform on the transformed two-dimensional frequency domain signal to obtain a focused image of the aircraft.

[0129] In order to better illustrate the beneficial effects of the present invention, the following simulation experiments were carried out:

[0130] For example, the following parameters in Table 1 can be used to perform simulation experiments to obtain Figure 6 The imaging scene diagram shown.

[0131] Table 1

[0132]

[0133]

[0134] For example, Figure 6 The ordinate is the azimuth dimension, and the abscissa is the distance dimension. Figure 6 The imaging image shown in (a) and Figure 6From the point target interpolation diagram shown in (b), it can be seen that the nine target points at different positions in the imaging scene can be clearly distinguished.

[0135] Therefore, since the high-precision instantaneous slant range model provided by the present invention is constructed based on the spiral trajectory geometric model, the speed and acceleration changes of the aircraft moving on a spiral trajectory are fully taken into account; therefore, a compensation function is constructed through the high-precision instantaneous slant range of the aircraft and the echo signal is compensated by this compensation function, which can improve the compensation effect of the compensation function and thus improve the imaging quality of the spiral trajectory; removing the coupled space-varying error in the phase by non-uniform fast Fourier transform can also improve the quality and accuracy of imaging.

[0136] Figure 7 FIG. 1 is a schematic diagram of the structure of an electronic device provided by an embodiment of the present invention. Figure 7 The electronic device 700 shown may include: at least one processor 710 ( Figure 7 Only one processor is shown in the figure), a memory 720, and a computer program 730 stored in the memory 720 and executable on the at least one processor 710, wherein the processor 710 implements the steps of any of the above-mentioned method embodiments when executing the computer program 730.

[0137] The electronic device 700 may be a processing device such as a robot that can implement the above method. The embodiment of the present invention does not impose any limitation on the specific type of the electronic device.

[0138] Those skilled in the art will understand that Figure 7 The electronic device 700 is merely an example and does not constitute a limitation on the electronic device. The electronic device 700 may include more or fewer components than shown in the figure, or may combine certain components, or may include different components. For example, the electronic device 700 may also include an input and output interface.

[0139] The processor 710 may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASTC), field programmable gate arrays (FPGA) or other programmable logic devices, discrete gates or transistor logic devices, discrete hardware components, etc. A general-purpose processor may be a microprocessor or any conventional processor, etc.

[0140] The memory 720 may be an internal storage unit in some embodiments, such as a hard disk or a memory. The memory 720 may also be an external storage device in other embodiments, such as a plug-in hard disk, a smart memory card (SmartMemory Card, SMC), a secure digital (Secure Digital, SD) card, a flash card (Flash Card), etc. Further, the memory 720 may also include both an internal storage unit and an external storage device. The memory 720 is used to store an operating system, an application program, a boot loader (Boot Loader), data, and other programs, such as the program code of the computer program, etc. The memory 720 may also be used to temporarily store data that has been output or is to be output.

[0141] It should be understood that the order of execution of the steps in the above embodiment does not necessarily mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiment of the present invention.

[0142] Those skilled in the art can clearly understand that for the convenience and simplicity of description, only the division of the above-mentioned functional units and modules is used as an example for illustration. In practical applications, the above-mentioned function allocation can be completed by different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above. The functional units and modules in the embodiment can be integrated into a processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The above-mentioned integrated unit can be implemented in the form of hardware or in the form of software functional units. In addition, the specific names of the functional units and modules are only for the convenience of distinguishing each other, and are not used to limit the scope of protection of the present invention. The specific working process of the units and modules in the above-mentioned system can refer to the corresponding process in the aforementioned method embodiment, which will not be repeated here.

[0143] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described or recorded in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0144] Those skilled in the art will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the present invention.

Claims

1. A spiral trajectory gliding aircraft synthetic aperture radar imaging method, characterized in that: include: The echo signal is compensated in the time domain and the frequency domain by using the time domain compensation function and the frequency domain compensation function to obtain a two-dimensional frequency domain signal; The time domain compensation function and the frequency domain compensation function are constructed based on the relationship between the high-precision instantaneous slant distance of any point in the imaging scene and the instantaneous slant distance of the reference point, and the instantaneous slant distance is determined based on a spiral trajectory geometric model with fast acceleration and velocity changes; Performing non-uniform fast Fourier transform on the two-dimensional frequency domain signal to obtain a transformed two-dimensional frequency domain signal; The transformed two-dimensional frequency domain signal is subjected to inverse Fourier transform to obtain a focused image.

2. The method according to claim 1, characterized in that The high-precision instantaneous slant range is determined according to a high-precision instantaneous slant range model, and the high-precision instantaneous slant range model is obtained by fitting and simplifying the multi-dimensional Taylor expansion coefficients of the instantaneous slant range.

3. The method according to claim 2, characterized in that The high-precision instantaneous slant range model satisfies the following formula: |r A ′(η)| is the high-precision instantaneous slant distance of any point A in the imaging scene, |r C (η)| is the instantaneous slant distance of the reference point C, and η is the azimuth slow time; in: ν n , g n , e n 、m n are the fitting coefficients of the multidimensional Taylor expansion coefficients of the 0th to 4th order terms of the instantaneous slope distance of the point A, is the Taylor expansion coefficient of the instantaneous slope distance of the reference point C, is the Taylor expansion coefficient of the instantaneous slant distance of the point A, wherein the multidimensional Taylor expansion coefficient is obtained by performing Taylor expansion based on the reference point.

4. The method according to claim 3, characterized in that The simplified multidimensional Taylor expansion coefficients satisfy the following formula: Among them, n (η)(n=0,1,2,3,4) is the multi-dimensional Taylor expansion coefficient of the point A.

5. The method according to claim 3, characterized in that: The method of performing compensation processing in the time domain and the frequency domain on the echo signal in sequence by using the time domain compensation function and the frequency domain compensation function to obtain a two-dimensional frequency domain signal includes: Performing time domain consistent compensation processing on the echo signal by using the time domain compensation function to obtain a time domain compensated signal; Based on the stationary phase principle, the echo two-dimensional frequency domain signal is obtained according to the time domain compensation signal; The two-dimensional frequency domain signal is obtained by performing frequency domain consistency compensation processing on the echo two-dimensional frequency domain signal in the two-dimensional frequency domain through the frequency domain compensation function.

6. The method according to claim 5, characterized in that The time domain compensation function satisfies the following formula: Among them, H0(f r ,η) is the time domain compensation function, j is the imaginary unit, f c is the carrier frequency, f r is the distance frequency, c represents the speed of light; The time domain compensation signal satisfies the following formula: Among them, s2(f r ,η) is the time domain compensation signal, κ0 is the scattering coefficient, ω r is the distance window function, ω a is the azimuth window function.

7. The method according to claim 6, characterized in that The frequency domain compensation function satisfies the following formula: Among them, H1(f r ,f η ) is the frequency domain compensation function, f τ =(f r +f c ) / c,f η is the azimuth frequency, is the expansion coefficient.

8. The method according to claim 7, characterized in that The process of the non-uniform fast Fourier transform is expressed as: Among them, s5(p,q) is the two-dimensional frequency domain signal after the transformation, s4(f r ,f η ) is the two-dimensional frequency domain signal, is the first frequency domain expansion coefficient, Δζ0 is the 0th expansion coefficient based on the reference point, is the second frequency domain expansion coefficient, and Δζ is the first-order expansion coefficient based on the reference point.

9. A spiral trajectory gliding aircraft synthetic aperture radar imaging device, characterized in that: include: A compensation module, wherein the compensation module is used to perform compensation processing in the time domain and the frequency domain on the echo signal in sequence through a time domain compensation function and a frequency domain compensation function to obtain a two-dimensional frequency domain signal; The time domain compensation function and the frequency domain compensation function are constructed based on the relationship between the high-precision instantaneous slant distance of any point in the imaging scene and the instantaneous slant distance of the reference point, and the instantaneous slant distance is determined based on a spiral trajectory geometric model with fast acceleration and velocity changes; A Fourier transform module is used to perform a non-uniform fast Fourier transform on the two-dimensional frequency domain signal to obtain a transformed two-dimensional frequency domain signal; and perform an inverse Fourier transform on the transformed two-dimensional frequency domain signal to obtain a focused image of the aircraft.

10. An electronic device comprising a memory, a processor and a computer program stored in the memory, characterized in that: When the processor executes the computer program, the method according to any one of claims 1 to 8 is implemented.

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