Sea surface ship target SAR (Synthetic Aperture Radar) image rapid simulation method and device and electronic equipment

Abstract

The invention relates to a sea surface ship target SAR image rapid simulation method and device and electronic equipment. The method comprises the steps that a geometric model of a ship target and model parameters corresponding to the geometric model are acquired; constructing a geometric scene of the ship target according to the model parameters of the ship target geometric model; performing echo simulation in the geometric scene by using the incident excitation source, and calculating to obtain a transfer function of the naval vessel target; a linear frequency modulation signal frequency spectrum is obtained, and SAR frequency domain echoes of the naval vessel target are obtained in combination with the transfer function; performing inverse Fourier transform on the SAR frequency domain echo to obtain an SAR time domain echo; and processing the SAR time domain echo by adopting a distance-Doppler algorithm to obtain an SAR image of the naval vessel target. According to the method, by introducing the system transfer function, the situation that a large amount of time is spent for sampling is effectively avoided, the calculation efficiency is improved, and the simulation efficiency of the SAR image method is remarkably improved on the premise that the simulation precision is guaranteed.

Description

Technical Field

[0001] The present application relates to the field of radar signal processing technology, and in particular to a method, device and electronic equipment for rapid simulation of SAR images of surface ship targets. Background Art

[0002] Synthetic Aperture Radar (SAR) is a high-resolution earth observation system based on microwave remote sensing. Compared with traditional spectral remote sensing, it has a certain ability to penetrate the atmosphere and the surface, and can work all day and all weather. It has been widely used in resource exploration, climate observation, military monitoring and other fields. With the rapid development of artificial intelligence, the detection and recognition of sea surface ship targets based on SAR images has become a hot topic of research at home and abroad. Using electromagnetic simulation algorithms and computers to simulate the SAR images of sea surface ship targets and construct a complete SAR image data set of ship targets is an effective way to solve the problem of insufficient measured SAR image data. It will help extract target features, improve target classification and recognition accuracy, and save experimental costs. However, the existing SAR image simulation of sea surface ship targets based on the time domain bouncing ray algorithm will generate a large number of time sampling points when combined with linear frequency modulation signals for SAR echo simulation, resulting in a huge amount of calculation, increasing the simulation calculation time, and resulting in low efficiency of SAR image simulation. Summary of the invention

[0003] In order to overcome the above-mentioned deficiencies of the prior art, the present application provides a method, device and electronic equipment for rapid simulation of SAR images of sea surface ship targets, which specifically adopts the following technical solutions:

[0004] A method for rapid simulation of SAR images of sea surface ship targets, characterized by comprising the following steps:

[0005] Acquire a geometric model of the ship target and model parameters of the corresponding geometric model; the model parameters at least include sea surface length, sea surface width, wind speed, wind direction, ship target position and heading, as well as SAR antenna polarization mode, working mode, radar platform height, radar movement speed, Leda scanning strip width and radar sampling rate;

[0006] Constructing a geometric scene of the ship target according to model parameters of the ship target geometric model;

[0007] Using incident excitation source to simulate echo in geometric scene, the transfer function of ship target is calculated;

[0008] Obtain the spectrum of the linear frequency modulation signal and combine it with the transfer function to obtain the SAR frequency domain echo of the ship target;

[0009] Perform inverse Fourier transform on SAR frequency domain echo to obtain SAR time domain echo;

[0010] The range-Doppler algorithm is used to process the SAR time domain echo to obtain the SAR image of the ship target.

[0011] Optional: When using an incident excitation source to simulate echoes in a geometric scene, set the baseband signal emitted by the radar to s t (t), then the echo signal s received by the SAR after scattering r (t) is:

[0012]

[0013] Then, based on the relationship between the baseband signal received by SAR and the original signal and the antenna movement process, the antenna movement time t a As the independent variable of the signal echo, the echo signal s received by SAR is taken r (t) Convert to two-dimensional form:

[0014]

[0015] where s t (t) is the baseband signal transmitted by SAR; s r (t) is the echo signal received by SAR; s r (t,t a ) is the two-dimensional echo signal received by SAR; N represents the total number of scattering sources in the geometric scene, i is a single independent scattering source; σ i (t) is the time domain transient response of the i-th scattering source in the geometric scene; t is the baseband signal transmission time; τ(t a ) is the time delay of the baseband signal from the antenna to the return, where τ(t a )=2R(t a ) / c,R(t a ) is the distance from the antenna to a point in the geometric scene, c is the speed of light; exp[-j2πf c ·τ(t a )] is the phase shift of the carrier frequency of the transmitted signal, where f c is the center frequency of the carrier signal; j is the imaginary unit.

[0016] Optional: When the SAR frequency domain echo of the ship target is obtained by combining the linear frequency modulation signal spectrum with the transfer function, the echo signal received by the SAR is first time-shifted and separated according to the characteristics of the convolution operation and the impulse response:

[0017]

[0018] Then, the echo signal separated by time offset is Fourier transformed based on the range-frequency domain pulse coherence method to obtain the frequency domain echo signal:

[0019]

[0020] where s r (f,t a ) is the SAR frequency domain echo; σ i (f) is the frequency domain transient response of the i-th scattering source in the geometric scene, i.e., the transfer function; s t (f) is the transmitted signal; f is the frequency of the baseband signal.

[0021] Optional: The transfer function σ i (f) Calculation by time-domain bouncing ray algorithm:

[0022]

[0023] where σ i (f) is the transfer function; r is the distance from the scattering source to the receiving radar; FT[] is the Fourier transform; E s (f) is the scattered field that varies with frequency; E i (f) is the incident field that varies with frequency; E s (t) is the excitation signal; E i (t) is the system response.

[0024] Optional: When calculating the transfer function of the ship target, the OpenGL algorithm and the neighborhood search algorithm are used in parallel to accelerate the calculation of the ray tracing stage in the time domain bouncing ray algorithm.

[0025] Optionally, the time-domain bouncing ray algorithm is derived based on the frequency-domain bouncing ray algorithm, wherein the frequency-domain bouncing ray algorithm is used to process the scattering field of a single facet:

[0026]

[0027] Where c is the speed of light, j is an imaginary number, S is the scattering area of ​​a single surface element, and r is the distance from the scattering source to the receiving radar; is the scattered electric field; E inc is the incident electric field intensity; ω is the unit vector of the incident wave frequency; Δt is the time delay of scattering between the surface elements at different positions, is the unit vector of the incident direction; is the unit vector of the reflected wave direction; is the position vector of the midpoint of the surface element;

[0028] in According to the electrical parameters of the panel element, it is calculated as follows:

[0029]

[0030] Where R TE is the reflection coefficient of the parallel component; R TM is the reflection coefficient of the vertical component; is the unit vector of the incident wave direction; is the unit vector parallel to the plane element direction; is the unit vector perpendicular to the plane element.

[0031] Optional: Perform an inverse Fourier transform based on the frequency domain bouncing ray algorithm and separate the time delays to obtain:

[0032]

[0033] Then, based on Radon transform, we can derive:

[0034]

[0035] Where c is the speed of light, j is an imaginary number, S is the scattering area of ​​a single surface element, and r is the distance from the scattering source to the receiving radar; is the scattered electric field; E inc is the incident electric field intensity; ΔS is the area of ​​the integral surface element; t1, t2, and t3 are the times when the electromagnetic wave irradiates the three corner points of the surface element.

[0036] Optionally: the incident excitation source uses a modulated Gaussian pulse.

[0037] Furthermore, the present application also discloses a rapid simulation device for SAR images of sea surface ship targets, the device comprising:

[0038] A parameter acquisition module is used to acquire the geometric model of the ship target and the model parameters of the corresponding geometric model; the model parameters at least include the length of the sea surface, the width of the sea surface, the wind speed, the wind direction, the position and heading of the ship target, and the polarization mode of the SAR antenna, the working mode, the radar platform height, the radar movement speed, the Leda scanning strip width and the radar sampling rate;

[0039] A scene construction module, used for constructing a geometric scene of a ship target according to model parameters of the ship target geometric model;

[0040] The echo simulation module is used to use the modulated Gaussian pulse as the incident excitation source to perform echo simulation in the geometric scene and calculate the transfer function of the ship target;

[0041] The frequency domain echo calculation module is used to obtain the linear frequency modulation signal spectrum and obtain the SAR frequency domain echo of the ship target in combination with the transfer function;

[0042] A time domain echo calculation module is used to perform inverse Fourier transform on the SAR frequency domain echo to obtain the SAR time domain echo;

[0043] The SAR image output module is used to process the SAR time domain echo using the range-Doppler algorithm to obtain the SAR image of the ship target.

[0044] Furthermore, the present application also discloses an electronic device, comprising a processor, a memory, and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of the above method when executing the computer program.

[0045] Beneficial Effects

[0046] The technical solution of this application has the following beneficial effects:

[0047] (1) The fast simulation method of SAR image of sea surface ship target proposed in this application can effectively avoid a large amount of time sampling caused by directly using wide pulse linear frequency modulation signal as excitation by introducing system transfer function, thereby improving calculation efficiency. And on this basis, the closed-form key integral expression of the transient scattering field of the medium target is analytically derived for SAR echo simulation of composite scene of sea surface ship target, ensuring image accuracy.

[0048] (2) The fast simulation method for SAR images of surface ship targets proposed in this application can significantly improve the simulation efficiency of the SAR image method while ensuring the simulation accuracy. Compared with the traditional method, the simulation efficiency is increased by more than 3 times, showing excellent performance in acquiring SAR images of surface ship targets. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 Schematic diagram of the process of rapid simulation method of SAR image of sea surface ship target in the embodiment of the present application.

[0050] Figure 2 This is a schematic diagram of an image obtained by performing a rapid simulation of a SAR image in an embodiment of the present application.

[0051] Figure 3 Schematic diagram of the image obtained by fast simulation of SAR images based on traditional frequency domain method.

[0052] Figure 4 Schematic diagram of the structure of the rapid simulation device for SAR image of sea surface ship target in the embodiment of the present application.

[0053] Figure 5 This is a structural diagram of an electronic device in an embodiment of the present application. DETAILED DESCRIPTION

[0054] The present application is further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application, and cannot be used to limit the scope of protection of the present application. It should be noted that the following detailed descriptions are all exemplary and are intended to provide further explanation of the present application.

[0055] Combination Figure 1 As shown, the embodiment of the present application specifically discloses a method for rapid simulation of SAR images of sea surface ship targets, which is characterized by comprising the following steps:

[0056] Step 1: Obtain the geometric model of the ship target and the model parameters of the corresponding geometric model; the model parameters at least include the length of the sea surface, the width of the sea surface, the wind speed, the wind direction, the position and heading of the ship target, and the polarization mode of the SAR antenna, the working mode, the radar platform height, the radar movement speed, the Leda scanning strip width and the radar sampling rate;

[0057] Step 2: constructing a geometric scene of the ship target according to the model parameters of the ship target geometric model;

[0058] Step 3: Use the incident excitation source to simulate the echo in the geometric scene and calculate the transfer function of the ship target;

[0059] Step 4: Obtain the spectrum of the linear frequency modulation signal and obtain the SAR frequency domain echo of the ship target in combination with the transfer function;

[0060] Step 5: Perform inverse Fourier transform on the SAR frequency domain echo to obtain the SAR time domain echo;

[0061] Step 6: Use the range-Doppler algorithm to process the SAR time domain echo to obtain the SAR image of the ship target.

[0062] In detail, in step 3 of the present application, since the SAR echo can be regarded as the convolution of the backscatter coefficient (scattering coefficient) of the entire SAR system and the point target echo in the time domain, it can be regarded as the product of the SAR system transfer function and the baseband signal spectrum in the frequency domain. Based on this principle, the embodiment of the present application uses an incident excitation source combined with a time domain SBR (Shooting and Bouncing Rays) algorithm to accelerate the calculation of the transfer function, wherein the present application preferably uses a modulated Gaussian pulse (duration in microseconds) as the excitation source. Specifically, in the present application, when using an incident excitation source to perform echo simulation in a geometric scene, the baseband signal emitted by the radar is set to s t (t), then the echo signal s received by the SAR after scattering r (t) is:

[0063]

[0064] Then, based on the relationship between the baseband signal received by SAR and the original signal and the antenna movement process, the antenna movement time t a As the independent variable of the signal echo, the echo signal s received by SAR is taken r (t) Convert to two-dimensional form:

[0065]

[0066] where s t (t) is the baseband signal transmitted by SAR; s r (t) is the echo signal received by SAR; s r (t,t a ) is the two-dimensional echo signal received by SAR; N represents the total number of scattering sources in the geometric scene, i is a single independent scattering source; σ i (t) is the time domain transient response of the i-th scattering source in the geometric scene; t is the baseband signal transmission time; τ(t a ) is the time delay of the baseband signal from the antenna to the return, where τ(t a )=2R(t a ) / c,R(t a ) is the distance from the antenna to a point in the geometric scene, c is the speed of light; exp[-j2πf c ·τ(t a )] is the phase shift of the carrier frequency of the transmitted signal, where f c is the center frequency of the carrier signal; j is the imaginary unit.

[0067] Then, in step 3, the present application performs derivation based on the range frequency-domain pulse coherence method (RFPC) and separates the system transfer function in the RFPC calculation formula:

[0068] First, according to the characteristics of convolution operation and impulse response, the echo signal received by SAR is time-shifted and separated:

[0069]

[0070] Then, the echo signal separated by time offset is Fourier transformed based on the range-frequency domain pulse coherence method to obtain the frequency domain echo signal:

[0071]

[0072] where s r (f,t a ) is the SAR frequency domain echo; σ i (f) is the frequency domain transient response of the i-th scattering source in the geometric scene, i.e., the transfer function; s t(f) is the transmitted signal; f is the frequency of the baseband signal.

[0073] Then the transfer function of the system can be separated based on the above derivation process.

[0074] It should be noted that s t (f) is given by the LFM (Linear Frequency-Modulated) signal, but it does not participate in the time domain SBR algorithm to solve the transfer function, but only participates in simple multiplication. Therefore, in the scattered echo, it retains the advantages of high average power and long propagation distance of the linear frequency modulation function, while avoiding the large amount of computational cost caused by the LFM signal as the incident source.

[0075] Furthermore, the transfer function σ described in this application i (f) Calculation by time-domain bouncing ray algorithm:

[0076]

[0077] where σ i (f) is the transfer function; r is the distance from the scattering source to the receiving radar; FT[] is the Fourier transform; E s (f) is the scattered field that varies with frequency; E i (f) is the incident field that varies with frequency; E i (t) is the excitation signal; E s (t) is the system response. It should be noted that in this application, since the far-field RCS (Radar Cross-Section) of a specific target does not change with the signal form, it can be calculated from any excitation signal. The excitation signal E of the transfer function in this application is i (t) Selecting modulated Gaussian pulses and combining them with the time domain SBR method can efficiently calculate the system response E at this time s (t), and then calculate the transfer function σ i (f).

[0078] Furthermore, in the present application, when calculating the transfer function of the ship target, the OpenGL algorithm and the neighborhood search algorithm are used in parallel to accelerate the calculation of the ray tracing stage in the time domain bouncing ray algorithm.

[0079] Furthermore, in this application, since the time-domain bouncing ray algorithm is derived based on the frequency-domain bouncing ray algorithm, the frequency-domain bouncing ray algorithm is first used to process the scattering field of a single facet:

[0080]

[0081] Where c is the speed of light, j is an imaginary number, S is the scattering area of ​​a single surface element, and r is the distance from the scattering source to the receiving radar; is the scattered electric field; E inc is the incident electric field intensity; ω is the unit vector of the incident wave frequency; Δt is the time delay of scattering between the surface elements at different positions, is the unit vector of the incident direction; is the unit vector of the reflected wave direction; is the position vector of the midpoint of the surface element;

[0082] in Independent of the integral term, it is calculated based on the electrical parameters of the surface element (such as the reflection coefficient, the surface element normal vector, the unit vector of the incident reflected wave direction, and the unit vector of the reflected wave direction):

[0083]

[0084] Where R TE is the reflection coefficient of the parallel component; R TM is the reflection coefficient of the vertical component; is the unit vector of the incident wave direction; is the unit vector parallel to the plane element direction; is the unit vector perpendicular to the plane element.

[0085] Then, based on the frequency domain bouncing ray algorithm, the inverse Fourier transform is performed and the time delay is separated to obtain:

[0086]

[0087] It should be noted that the accuracy of the integral term in the above formula depends on the fineness of the subdivision surface element.

[0088] Therefore, the present application further derives a closed-form analytical solution based on Radon transform, so that the calculation accuracy of the integral term is independent of frequency and is applicable to the scattering results of triangular facets of any size. Then, the closed-form analytical solution is substituted into the above formula to obtain:

[0089]

[0090] Where c is the speed of light, j is an imaginary number, S is the scattering area of ​​a single surface element, and r is the distance from the scattering source to the receiving radar; is the scattered electric field; E inc is the incident electric field intensity; ΔS is the area of ​​the integrated surface element; t1, t2, and t3 are the times when the electromagnetic wave irradiates the three corner points of the surface element. It should be noted that the unit vectors of the three corner points of the surface element are set as Then the time it takes for the electromagnetic wave to irradiate the three corner points of the surface element can be expressed as:

[0091]

[0092] in is the unit vector of the incident direction; is the unit vector of the reflected wave direction; c is the speed of light.

[0093] In addition, the present application also compares the SAR imaging results by using the method proposed in the present application and the traditional frequency domain-based method, and the specific parameters are shown in Table 1.

[0094] Table 1

[0095]

[0096] from Figure 2 and Figure 3 It can be seen from the results that the imaging results obtained by the simulation based on the method of this application well reflect the scattering structure of the ship. At the same time, the calculation time of the two methods is counted: the simulation time of the method of this application is 9.1 minutes, and the simulation time of the traditional method based on the frequency domain is 28.66 minutes, and the acceleration ratio is 3.1, which shows that the method proposed in this application is obviously more efficient than the traditional simulation method based on the frequency domain method.

[0097] Further, combined with Figure 4 As shown, the present application also discloses a rapid simulation device for SAR images of sea surface ship targets, the device comprising:

[0098] A parameter acquisition module is used to acquire the geometric model of the ship target and the model parameters of the corresponding geometric model; the model parameters at least include the length of the sea surface, the width of the sea surface, the wind speed, the wind direction, the position and heading of the ship target, and the polarization mode of the SAR antenna, the working mode, the radar platform height, the radar movement speed, the Leda scanning strip width and the radar sampling rate;

[0099] A scene construction module, used for constructing a geometric scene of a ship target according to model parameters of the ship target geometric model;

[0100] The echo simulation module is used to use the modulated Gaussian pulse as the incident excitation source to perform echo simulation in the geometric scene and calculate the transfer function of the ship target;

[0101] The frequency domain echo calculation module is used to obtain the linear frequency modulation signal spectrum and obtain the SAR frequency domain echo of the ship target in combination with the transfer function;

[0102] A time domain echo calculation module is used to perform inverse Fourier transform on the SAR frequency domain echo to obtain the SAR time domain echo;

[0103] The SAR image output module is used to process the SAR time domain echo using the range-Doppler algorithm to obtain the SAR image of the ship target.

[0104] The device provided in the embodiment of the present application can achieve Figure 1 To avoid repetition, the various processes implemented by the method embodiment will not be described again here.

[0105] like Figure 5 As shown, the embodiment of the present application also provides an electronic device, including a processor 701, a memory 702 and a bus 703, wherein the processor 701 and the memory 702 communicate with each other through the bus 703; and a program or instruction stored in the memory 702 and executable on the processor 701, which is executed by the processor 701 to implement the following Figure 1 The various processes of the method embodiment shown in the figure can achieve the same technical effect. To avoid repetition, they will not be described again here.

[0106] The embodiment of the present application also provides a readable storage medium on which a program or instruction is stored. When the program or instruction is executed by a processor, the above Figure 1 The various processes of the method embodiments described above can achieve the same technical effect, and will not be described again here to avoid repetition.

[0107] The present application also provides a computer program product, including computer instructions, which, when executed by a processor, implement the above Figure 1 The various processes of the method embodiments described above can achieve the same technical effect, and will not be described again here to avoid repetition.

[0108] It should be understood that "one embodiment" or "an embodiment" mentioned throughout the specification means that specific features, structures or characteristics related to the embodiment are included in at least one embodiment of the present application. Therefore, "in one embodiment" or "in an embodiment" appearing throughout the specification does not necessarily refer to the same embodiment. In addition, these specific features, structures or characteristics can be combined in one or more embodiments in any suitable manner. It should be understood that in various embodiments of the present application, the size of the sequence number of the above-mentioned processes does not mean the order of execution, and 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 embodiments of the present application. The above-mentioned sequence numbers of the embodiments of the present application are only for description and do not represent the advantages and disadvantages of the embodiments.

[0109] It should be noted that, in this article, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the sentence "comprises a ..." does not exclude the existence of other identical elements in the process, method, article or device including the element.

[0110] In the several embodiments provided in the present application, it should be understood that the disclosed devices and methods can be implemented in other ways. The device embodiments described above are only schematic. For example, the division of the units is only a logical function division. There may be other division methods in actual implementation, such as: multiple units or components can be combined, or can be integrated into another device, or some features can be ignored or not executed. In addition, the coupling, direct coupling, or communication connection between the components shown or discussed can be through some interfaces, and the indirect coupling or communication connection of the devices or units can be electrical, mechanical or other forms.

[0111] The units described above as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units; they may be located in one place or distributed on multiple network units; some or all of the units may be selected according to actual needs to achieve the purpose of the present embodiment.

[0112] In addition, all functional units in the embodiments of the present application may be integrated into one processing unit, or each unit may be a separate unit, or two or more units may be integrated into one unit; the above-mentioned integrated units may be implemented in the form of hardware or in the form of hardware plus software functional units.

[0113] A person skilled in the art can understand that all or part of the steps of implementing the above method embodiment can be completed by hardware related to program instructions, and the aforementioned program can be stored in a computer-readable storage medium. When the program is executed, it executes the steps of the above method embodiment; and the aforementioned storage medium includes: mobile storage devices, read-only memories (ROM), magnetic disks or optical disks, etc., various media that can store program codes.

[0114] Alternatively, if the above-mentioned integrated unit of the present application is implemented in the form of a software function module and sold or used as an independent product, it can also be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the embodiment of the present application can essentially or in other words, the part that contributes to the prior art can be embodied in the form of a software product, which is stored in a storage medium and includes several instructions for a device (which can be a terminal or a platform, etc.) to execute all or part of the methods described in each embodiment of the present application. The aforementioned storage medium includes: various media that can store program codes, such as mobile storage devices, ROMs, magnetic disks, or optical disks.

[0115] The above is only a preferred implementation of the present application. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present application. These improvements and modifications should also be regarded as the scope of protection of the present application.

Claims

1. A method for rapid simulation of SAR images of sea surface ship targets, characterized in that: The steps include: Acquire a geometric model of the ship target and model parameters of the corresponding geometric model; the model parameters at least include sea surface length, sea surface width, wind speed, wind direction, ship target position and heading, as well as SAR antenna polarization mode, working mode, radar platform height, radar movement speed, Leda scanning strip width and radar sampling rate; Constructing a geometric scene of the ship target according to model parameters of the ship target geometric model; Using incident excitation source to simulate echo in geometric scene, the transfer function of ship target is calculated; Obtain the spectrum of the linear frequency modulation signal and combine it with the transfer function to obtain the SAR frequency domain echo of the ship target; Perform inverse Fourier transform on SAR frequency domain echo to obtain SAR time domain echo; The range-Doppler algorithm is used to process the SAR time domain echo to obtain the SAR image of the ship target.

2. The method for rapid simulation of SAR images of sea surface ship targets according to claim 1 is characterized in that: When using the incident excitation source to simulate the echo in a geometric scene, the baseband signal emitted by the radar is set to s t (t), then the echo signal s received by the SAR after scattering r (t) is: Then, based on the relationship between the baseband signal received by SAR and the original signal and the antenna movement process, the antenna movement time t a As the independent variable of the signal echo, the echo signal s received by SAR is taken r (t) Convert to two-dimensional form: where s t (t) is the baseband signal transmitted by SAR; s r (t) is the echo signal received by SAR; s r (t,t a ) is the two-dimensional echo signal received by SAR; N represents the total number of scattering sources in the geometric scene, i is a single independent scattering source; σ i (t) is the time domain transient response of the i-th scattering source in the geometric scene; t is the baseband signal transmission time; τ(t a ) is the time delay of the baseband signal from the antenna to the return, where τ(t a )=2R(t a ) / c,R(t a ) is the distance from the antenna to a point in the geometric scene, c is the speed of light; exp[-j2πf c ·τ(t a )] is the phase shift of the carrier frequency of the transmitted signal, where f c is the center frequency of the carrier signal; j is the imaginary unit.

3. The method for rapid simulation of SAR images of sea surface ship targets according to claim 2 is characterized in that: When combining the linear frequency modulation signal spectrum with the transfer function to obtain the SAR frequency domain echo of the ship target, firstly, the echo signal received by the SAR is time-shifted and separated according to the characteristics of the convolution operation and the impulse response: Then, the echo signal separated by time offset is Fourier transformed based on the range-frequency domain pulse coherence method to obtain the frequency domain echo signal: where s r (f,t a ) is the SAR frequency domain echo; σ i (f) is the frequency domain transient response of the i-th scattering source in the geometric scene, i.e., the transfer function; s t (f) is the transmitted signal; f is the frequency of the baseband signal.

4. The method for rapid simulation of SAR images of sea surface ship targets according to claim 3 is characterized in that: The transfer function σ i (f) Calculation by time-domain bouncing ray algorithm: where σ i (f) is the transfer function; r is the distance from the scattering source to the receiving radar; FT[] is the Fourier transform; E s (f) is the scattered field that varies with frequency; E i (f) is the incident field that varies with frequency; E s (t) is the excitation signal; E i (t) is the system response.

5. The method for rapid simulation of SAR images of sea surface ship targets according to claim 4 is characterized in that: When calculating the transfer function of the ship target, the OpenGL algorithm and the neighborhood search algorithm are used in parallel to accelerate the calculation of the ray tracing stage in the time domain bouncing ray algorithm.

6. The method for rapid simulation of SAR images of sea surface ship targets according to claim 5 is characterized in that: The time domain bouncing ray algorithm is derived based on the frequency domain bouncing ray algorithm, where the frequency domain bouncing ray algorithm is used to process the scattering field of a single surface element: Where c is the speed of light, j is an imaginary number, S is the scattering area of ​​a single surface element, and r is the distance from the scattering source to the receiving radar; is the scattered electric field; E inc is the incident electric field intensity; ω is the unit vector of the incident wave frequency; Δt is the time delay of scattering between the surface elements at different positions, is the unit vector of the incident direction; is the unit vector of the reflected wave direction; is the position vector of the midpoint of the surface element; in Calculated according to the electrical parameters of the panel element: Where R TE is the reflection coefficient of the parallel component; R TM is the reflection coefficient of the vertical component; is the unit vector of the incident wave direction; is the unit vector parallel to the plane element direction; is the unit vector perpendicular to the plane element.

7. The method for rapid simulation of SAR images of sea surface ship targets according to claim 6 is characterized in that: Based on the frequency domain bouncing ray algorithm, the inverse Fourier transform is performed and the time delay is separated to obtain: Then based on Radon transform, we can derive: Where c is the speed of light, j is an imaginary number, S is the scattering area of ​​a single surface element, and r is the distance from the scattering source to the receiving radar; is the scattered electric field; E inc is the incident electric field intensity; ΔS is the area of ​​the integral surface element; t1, t2, and t3 are the times when the electromagnetic wave irradiates the three corner points of the surface element.

8. The method for rapid simulation of SAR images of sea surface ship targets according to claim 1 is characterized in that: The incident excitation source is a modulated Gaussian pulse.

9. A rapid simulation device for SAR images of sea surface ship targets, characterized in that: The device comprises: A parameter acquisition module is used to acquire the geometric model of the ship target and the model parameters of the corresponding geometric model; the model parameters at least include the length of the sea surface, the width of the sea surface, the wind speed, the wind direction, the position and heading of the ship target, and the polarization mode of the SAR antenna, the working mode, the radar platform height, the radar movement speed, the Leda scanning strip width and the radar sampling rate; A scene construction module, used for constructing a geometric scene of a ship target according to model parameters of the ship target geometric model; The echo simulation module is used to use the modulated Gaussian pulse as the incident excitation source to perform echo simulation in the geometric scene and calculate the transfer function of the ship target; The frequency domain echo calculation module is used to obtain the linear frequency modulation signal spectrum and obtain the SAR frequency domain echo of the ship target in combination with the transfer function; A time domain echo calculation module is used to perform inverse Fourier transform on the SAR frequency domain echo to obtain the SAR time domain echo; The SAR image output module is used to process the SAR time domain echo using the range-Doppler algorithm to obtain the SAR image of the ship target.

10. An electronic device comprising a processor, a memory, and a computer program stored in the memory and executable on the processor, wherein: When the processor executes the computer program, the steps of the method according to any one of claims 1 to 8 are implemented.

Images