SAR deception jamming method based on mixed domain efficient track migration compensation

Abstract

The application provides a SAR deception jamming method of mixed domain efficient track deviation compensation, comprising the following steps: after a SAR radar enters a detection range of a jammer, relevant parameters of the SAR radar are acquired, and a jammer deception template is constructed according to false electromagnetic features generated in a SAR image by jamming; azimuth focusing and range migration compensation calculation are performed on the jammer deception template in an azimuth frequency domain, and then inverse Fourier transform in the azimuth direction is performed to obtain an initialization template; after the SAR radar enters a jamming area, real-time modulation is performed, track deviation compensation is performed on the initialization template after coupling term decomposition in the azimuth time domain, and a real-time SAR system correlation filter is constructed in the azimuth time domain pulse by pulse; the real-time SAR system correlation filter and the jammer correlation filter are multiplied in a range frequency domain to obtain a non-linear track jamming frequency domain response function, and convolution operation is performed on the non-linear track SAR deception jamming signal obtained after the SAR signal intercepted to obtain a non-linear track SAR deception jamming signal.

Description

Technical Field

[0001] This invention belongs to the field of synthetic aperture radar countermeasures, and in particular relates to a SAR (Synthetic Aperture Radar) deception and jamming method based on efficient track offset compensation in the hybrid domain. Background Technology

[0002] Synthetic Aperture Radar (SAR) poses a significant threat to high-value strategic targets due to its advantages such as all-weather, all-day operation, high processing gain, and strong penetration capabilities. Therefore, there is an extremely urgent practical need to find ways to jam SAR reconnaissance and effectively protect important equipment and key locations from SAR surveillance.

[0003] SAR deception jamming is a crucial component of SAR jamming technology. It involves implanting false electromagnetic features into SAR radar images to confuse target identification without alerting the enemy, offering lower power consumption and more flexible application scenarios. Traditional SAR deception jamming primarily follows the ideal straight-line trajectory of the SAR signal, modulating and retransmitting the intercepted SAR signal to create a jamming signal. However, in actual flight, due to airflow disturbances and platform instability, SAR operates on a non-linear trajectory, typically employing motion-compensated imaging methods. If the jamming signal is modulated and retransmitted according to the ideal straight-line trajectory, the false target in the SAR deception jamming will exhibit positional shifts after range compression, main lobe broadening or paired echoes after azimuth compression, or even be submerged in clutter.

[0004] Existing efficient SAR deception jamming methods are all designed for straight-line trajectories. For non-linear SAR trajectories, deception jamming can only be achieved using the point-by-point superposition direct computation (SA) jamming method. While the SA method offers high accuracy due to its point-by-point calculations and lack of approximations, its low jamming signal generation efficiency makes it difficult to apply in practical SAR countermeasure systems. To address these shortcomings, this invention proposes a SAR deception jamming method based on efficient hybrid domain (EHD) track offset compensation. This method avoids the double integral operation in the SA method through fast Fourier transform (FFT) and complex multiplication, rapidly calculating the ideal track jamming frequency domain response function of the deception jamming template in the azimuth frequency domain. By decomposing the coupling term between the trajectory offset and the ideal straight-line track jamming frequency domain response function, flexible real-time trajectory offset compensation is performed in the azimuth time domain. This significantly improves signal generation efficiency while maintaining accuracy, solving the problem that existing SAR deception jamming techniques are unsuitable for non-linear trajectories or have low jamming signal generation efficiency, making them difficult to apply in practical SAR countermeasure systems. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a SAR deception jamming method based on efficient track offset compensation in a hybrid domain. After the SAR radar enters the jammer's detection range, relevant parameters of the SAR radar are acquired. Based on the false electromagnetic features that the jammer intends to generate in the SAR image, a jammer deception template is constructed. In the azimuth frequency domain, azimuth focusing and range migration compensation calculations are performed on the jammer deception template, followed by an inverse azimuth-to-Fourier transform to obtain an initialization template. Real-time modulation is performed after the SAR radar enters the jamming area. Track offset compensation is performed on the initialization template in the azimuth time domain after coupling term decomposition. A real-time SAR system correlation filter is constructed pulse-by-pulse in the azimuth time domain. The real-time SAR system correlation filter and the jammer correlation filter are multiplied in the range frequency domain to obtain a non-linear track jamming frequency domain response function. This function is then convolved with the intercepted SAR signal to obtain a non-linear track SAR deception jamming signal, which is then forwarded.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A hybrid-domain efficient SAR deception jamming method for track offset compensation includes the following steps:

[0008] Step 1: After the SAR radar enters the jammer's detection range, acquire the relevant parameters of the SAR radar, and construct a jammer deception template based on the false electromagnetic features that the jammer intends to generate in the SAR image.

[0009] Step 2: Perform azimuth focusing and range migration compensation calculations on the jammer deception template in the azimuth frequency domain, and then perform azimuth-to-Fourier inverse transform to obtain the initial template;

[0010] Step 3: Compensate for the track offset after decomposing the initial template in the azimuth time domain, and construct a real-time SAR radar parameter correlation filter pulse by pulse in the azimuth time domain;

[0011] Step 4: Multiply the real-time SAR radar parameter correlation filter and the jammer correlation filter in the range frequency domain to obtain the non-linear trajectory jamming frequency domain response function. Perform convolution operation with the intercepted SAR radar transmitted signal to obtain the non-linear trajectory SAR deception jamming signal, and then forward it.

[0012] Further, step one includes:

[0013] Step 1.1: Detect the relevant parameters of the SAR radar to be acquired. The relevant parameters include the following three types:

[0014] (1) Platform parameters: platform flight altitude H, platform speed v;

[0015] (2) Antenna parameters, antenna downward angle θ0, synthetic aperture length L a ;

[0016] (3) Signal parameters: signal carrier frequency f, signal bandwidth Δf, pulse duration T r and pulse repetition interval T p ;

[0017] After the SAR radar enters the detection range of the jammer, the relevant parameters of the SAR radar are initially obtained; the ideal straight track of the SAR is calculated and estimated through platform parameters and antenna parameters, and the interference frequency domain response function of the ideal straight track of the SAR is constructed through antenna parameters and signal parameters; when the jamming target is a non-straight track SAR, the non-straight track of the SAR is obtained pulse by pulse in the real-time modulation stage and the track offset is calculated for trajectory offset compensation, and the interference frequency domain response function of the actual non-straight track of the SAR is generated.

[0018] Step 1.2: Construct a jammer deception template based on the false electromagnetic features generated by the jammer in the SAR image;

[0019] The slant distance plane of the pre-interference region (x) P r P Equal-interval sampling is performed. Based on the false electromagnetic characteristics generated by the jammer in the SAR image, the radar backscattering coefficient of the false scattering center is set at each sampling location to obtain the jammer deception template σ[x]. P r P ]:

[0020] σ[x P r P ]=∑ m ∑ n σ(x P r P )·δ(x P -mΔu,r P -nΔv) (1)

[0021] Where, x P r P δ(·,·) represents the range and azimuth positions of the false point target in the pre-interference area, respectively. m and n are integers, representing the index of the false point target in the range and azimuth directions, respectively. δ(·,·) is a two-dimensional Dirac function. Δu and Δv represent the sampling intervals of the pre-interference area in the range and azimuth directions, respectively. ∑ is the summation symbol.

[0022] After detection, the SAR system correlation filter H is applied to non-linear flight paths. trans，P Generation of (x′, η); H of the traditional point-by-point superposition direct calculation method trans，P The expression for (x′, η) is:

[0023]

[0024] Where η=4πf r / c represents the spatial frequency of the range, rect(·) is the range-oriented rectangular window function, and T r Let w(·) be the signal pulse width, w(·) be the rectangular window function of the azimuth antenna pattern, and x be the signal pulse width. P r represents the azimuth position of the target point. P Let x' be the range position of the target point, x′ be the actual azimuth position of the SAR radar, j represent the imaginary unit, exp(·) is the exponential function, and c is the speed of light. L represents the distance-space bandwidth, Δf is the signal bandwidth, and L a Where λ is the synthetic aperture length and λ is the wavelength, ΔR(x′-x) P r P ) represents the azimuth spatial variation term in the ideal straight-line slant range at point P, and w(·) represents the antenna azimuth window gain;

[0025] By employing orientation-to-Fourier transform and substitution through the convolution theorem of time and frequency domain terms, FFT and complex multiplication are used to avoid the interference in the H function of the traditional frequency domain response function. trans，P The double integral operation of (x′, η) is performed; and by approximating the coupling term of the frequency domain response function of the trajectory deviation track and the ideal straight track interference through the beam center decomposition, the integral is simplified to obtain H. trans，P Efficient modulation method in the hybrid domain of (x′, η):

[0026]

[0027] Where, ψ(x′, r P ) represents the range-varying offset, and δr(x′) represents the scene-invariant track offset; G A (ξ,r P G represents the focusing depth term of the frequency domain response function to interference on an ideal straight-line trajectory. B (η) is the distance space frequency domain window function.

[0028] Furthermore, step two includes calculating the deception template azimuth frequency domain filter H after azimuth focusing and range migration compensation in the azimuth frequency domain. diff (ξ,r P Then, an inverse Fourier transform of the orientation is performed to obtain the initialization template H. ini (x′,r P );include:

[0029] Step 2.1, perform slant range and phase compensation on the deception template using an ideal straight-line trajectory:

[0030]

[0031] Among them, h P (x P r P This is a deception jamming template with ideal straight-line track slant range phase;

[0032] Step 2.2: Perform azimuth focusing and range migration compensation in the azimuth frequency domain to obtain the azimuth frequency domain expression of the interference frequency domain response function of the ideal straight-line track:

[0033] H diff (ξ,r P ) = G A (ξ,r P FT x (h P (x P r P (5)

[0034] Among them, G A (ξ,r P The focus depth term is represented by the following formula:

[0035]

[0036] Where j is the imaginary unit, ξ is the azimuth spatial frequency, and ξ = 2πf a / v, where f a Ω represents the azimuth frequency. x For azimuth space bandwidth, R0 is the slant distance from the scene center;

[0037] Step 2.3: Calculate the initialization template H using the inverse Fourier transform in the orientation direction. ini (x′,r P ):

[0038] H ini (x′,r P ) = IFT ξ [H diff (ξ,r P (7)

[0039] Among them, IFT ξ This is the inverse Fourier transform of the azimuth to the frequency domain.

[0040] Furthermore, step three includes: performing real-time modulation after the SAR radar enters the interference area, and performing range-space-variable offset ψ(x′, r) after decomposing the initial template coupling term in the azimuth time domain. P Compensation is performed on the scene-invariant track offset δr(x′), thereby constructing a real-time SAR system correlation filter H pulse-by-pulse in the azimuth time domain. trans，P (x′, η); including:

[0041] Step 3.1: Real-time detection of SAR track offset vector d(x′) and offset angle β(x′), and calculation of range spatially varying offset ψ(x′, r) at the current SAR position x′. P The calculation formulas for the scene-invariant track offset δr(x′) and the scene-invariant track offset are as follows:

[0042]

[0043]

[0044] Where θ0 is the antenna-down view of the scene center point, and Δr is the ground distance offset from the scene center point to the position of any false point target P in the pre-deception interference area.

[0045] Step 3.2, initialize template H at the current SAR location x′. ini (x′,r P ) Perform distance spatial offset ψ(x′, r P Compensation modulation, constructing the SAR system correlation filter H trans，P (x′, η), whose modulation formula is as follows:

[0046]

[0047]

[0048] Among them, GB (η) is the frequency domain window function of the distance space. This function is used to perform amplitude weighting in the frequency domain of the distance space. Its mathematical expression is:

[0049]

[0050] Furthermore, step four includes: applying the correlation filter H of the real-time SAR system. trans，P (x′, η) and the jammer-related filter H jamfilter Multiplying (x′, η) in the distance frequency domain yields the jammer's frequency domain response function H. jammer，P (x′, η), after convolution with the intercepted SAR radar transmission signal, is used to forward the non-linear SAR deception jamming signal; including:

[0051] Step 4.1, apply the correlation filter H of the real-time SAR system. trans，P (x′, η) and the jammer-related filter H jamfilter Multiplying (x′, η) in the distance frequency domain yields the jammer's frequency domain response function H. jammer，P (x′, η), the modulation operation expression is as follows:

[0052] H jammer，P (x′,η)=H trans，P (x′,η)·H jamfilter (x′,η) (12)

[0053] Among them, the jammer-related filter H jamfilter The formula for calculating (x′,η) is as follows:

[0054]

[0055] Where, x J r represents the azimuth position of the jammer. J Let x be the range position of the jammer. J R′ represents the azimuth position of the jammer. J The actual non-linear track slant distance of the jammer's location;

[0056] Step 4.2: Perform a frequency domain convolution operation between the intercepted SAR signal and the jammer's frequency domain response function to obtain the forwarding jamming signal.

[0057] S jammer，P (x P r P |x′)=IFT η {FT r [S jammer (x′|x J r J )]·H jammer，P(x′,η)} (14)

[0058] Among them, S jammer，P (x P r P |x′) represents the deception jamming signal targeted by jammer J in the pre-deception jamming area under SAR non-linear trajectory conditions, S jammer (x′|x J r J The ) represents the non-linear SAR signal intercepted by jammer J, IFT η For the inverse Fourier transform of the range to the frequency domain, FT r This is the Fourier transform from the distance domain to the time domain.

[0059] The main beneficial effects of this invention include:

[0060] First, this invention can effectively deceive and interfere with non-linear SAR tracks by compensating for track offsets in the azimuth and time domains, and the modulation calculation is flexible and simple.

[0061] Second, it has high computational efficiency. The calculations mainly include fast Fourier transform and complex multiplication. The computational load can meet the requirements for high-efficiency deception and interference modulation calculations in the initialization stage, real-time modulation stage, and interference signal forwarding stage.

[0062] Third, the interference signal has a good focusing effect, and the interference signal can achieve good focusing of false targets in a large scene area.

[0063] In summary, this invention is applicable to countering non-linear SAR, enabling deception and interference with large-area false scenes or scattered false targets. Attached Figure Description

[0064] Figure 1 This is a 3D view of a non-linear SAR spatial geometry model.

[0065] Figure 2 This is a 2D range profile view of a non-linear SAR spatial geometry model.

[0066] Figure 3 This is a flowchart of a SAR deception jamming method based on efficient track offset compensation in the hybrid domain;

[0067] Figure 4 This is a diagram showing the vertical and horizontal components of the SAR track offset for non-linear tracks.

[0068] Figure 5 This is a close-up image of the false target point P1;

[0069] Figure 6a This is the distance profile of the false target point P1;

[0070] Figure 6b This is the azimuth profile of the false target point P1;

[0071] Figure 7 This is a close-up image of the false target point P2;

[0072] Figure 8a This is the distance profile of the false target point P2;

[0073] Figure 8b This is the azimuth profile of the false target point P2;

[0074] Figure 9 This is a close-up image of the P3 false target point;

[0075] Figure 10a This is the distance profile of the P3 false target point;

[0076] Figure 10b This is the azimuth profile of the false target point P3;

[0077] Figure 11 It is a deceptive template using fake scenarios;

[0078] Figure 12a This is a magnified view of a fake scene deception template;

[0079] Figure 12b This is a magnified view of a false scene in a SAR radar image generated by the method of this invention. Detailed Implementation

[0080] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0081] like Figure 3 As shown, the present invention provides a hybrid domain efficient track offset compensation method for SAR deception and jamming, which mainly includes the following steps:

[0082] Step 1: Detection. After the SAR radar enters the jammer's detection range, the relevant parameters of the SAR radar are obtained. Based on the false electromagnetic features that the jammer intends to generate in the SAR image, a jammer deception template is constructed.

[0083] Step 2: Initialization. In the azimuth frequency domain, the jammer deception template is subjected to azimuth focusing and range migration compensation calculations, and then an inverse azimuth-to-Fourier transform is performed to obtain the initialization template.

[0084] Step 3: Real-time modulation after the SAR radar enters the interference area, track offset compensation after coupling term decomposition of the initial template in the azimuth time domain, and pulse-by-pulse construction of real-time SAR radar parameter correlation filter in the azimuth time domain.

[0085] Step 4: Forwarding the jamming signal. The real-time SAR radar parameter correlation filter and the jammer's correlation filter are multiplied in the range-frequency domain to obtain the non-linear trajectory jamming frequency domain response function. The intercepted SAR radar transmitted signal is converted into a SAR baseband digital signal through gain control, down-conversion, and analog-to-digital conversion. This signal is then convolved with the non-linear trajectory jamming frequency domain response function using Fourier transform to obtain the non-linear trajectory SAR deception jamming signal. Finally, after digital-to-analog conversion, up-conversion, and gain control, the jamming radio frequency signal is forwarded via the jammer's transmitting antenna.

[0086] The invention will be further explained below with reference to the accompanying drawings. Taking a front-looking SAR as an example, when a jammer interferes with a nonlinear trajectory SAR system, the geometric relationship between the SAR, the jammer, and the deception interference area is as follows: Figure 1 and Figure 2 As shown. The origin O of the spatial coordinate system is located at the flight start point of the SAR radar, and X′ is the position of the SAR radar. The x-axis points in the range direction, the y-axis points in the azimuth direction, and the z-axis points in the altitude direction. Vector d(x′) represents the offset vector of the non-linear trajectory relative to the ideal linear trajectory. The y and z components of vector d(x′) represent the horizontal and vertical offsets of the SAR flight platform relative to the ideal linear trajectory. β represents the angle of the flight trajectory offset relative to the ideal linear trajectory. The jammer is placed at J(x′). J r J θ J ), P(x P r P θ P Let be any false point target in the area to be deceived and interfered with, and let its scattering coefficient be σ(x). P r P ), where θ0 is the viewpoint from the SAR antenna at the center of the scene, θ P and θ J This is the local perspective of points P and J. R′ P (x′,x P r P ) and R P (x′,x P r P R′ represents the slant range from target P to the antenna in SAR radar positions for non-linear and nominal tracks, respectively. J (x′,x J r J ) represents the slant range from the jammer to the antenna for the SAR radar position on a non-linear trajectory, where δxr For target point P d The difference between the actual non-linear trajectory and the ideal straight trajectory, P d The slant range of the ideal straight-line track is equal to the shortest slant range of the ideal straight-line track at target point P. Here, H is the platform's flight altitude; θ0 is the antenna's downward angle of view.

[0087] Specifically, step one includes detection: after the SAR radar enters the detection range, relevant parameters of the SAR radar are acquired, and based on the false electromagnetic features that the jammer is intended to generate in the SAR image, a jammer deception template σ[x] is constructed. P r P ];

[0088] Step 1.1, the relevant parameters of the SAR radar to be acquired mainly include the following three types:

[0089] (1) Platform parameters: platform flight altitude H, platform speed v;

[0090] (2) Antenna parameters, antenna downward angle θ0, synthetic aperture length L a ;

[0091] (3) Signal parameters: signal carrier frequency f, signal bandwidth Δf, pulse duration T r and pulse repetition interval T p ;

[0092] After the SAR radar enters the jammer's detection range, its relevant parameters are initially acquired. The ideal straight-line trajectory of the SAR is calculated and predicted using platform and antenna parameters. The interference frequency domain response function for the ideal straight-line trajectory is then constructed using antenna and signal parameters. When the jamming target is a non-straight-line SAR, the non-straight-line trajectory needs to be acquired pulse-by-pulse during the real-time modulation stage, and the trajectory offset needs to be calculated for trajectory offset compensation, generating the interference frequency domain response function for the actual non-straight-line trajectory of the SAR.

[0093] Step 1.2: Construct a jammer deception template based on the false electromagnetic features generated by the jammer in the SAR image;

[0094] The slant distance plane of the pre-interference region (x) P r P Equal-interval sampling is performed. Based on the false electromagnetic characteristics generated by the jammer in the SAR image, the radar backscattering coefficient of the false scattering center is set at each sampling location to obtain the jammer deception template σ[x]. P r P ]:

[0095] σ[x P r P ]=∑ m ∑n σ(x P r P )·δ(x P -mΔu,r P -nΔv) (1)

[0096] Where, x P r P δ(·,·) represents the range and azimuth positions of the false point target in the pre-interference area, respectively. m and n are integers, representing the index of the false point target in the range and azimuth directions, respectively. δ(·,·) is a two-dimensional Dirac function. Δu and Δv represent the sampling intervals of the pre-interference area in the range and azimuth directions, respectively. Σ is the summation symbol.

[0097] After detection, the main focus is on the correlation filter H of the non-linear SAR system. trans，P Generation of (x′, η). The traditional point-by-point stacking direct computation (SA) method for H... trans，P The expression for (x′, η) is:

[0098]

[0099] Where η=4πf r / c represents the spatial frequency of the range, rect(·) is the range-oriented rectangular window function, and T r Let w(·) be the signal pulse width, w(·) be the rectangular window function of the antenna pattern, and x be the signal pulse width. P r represents the azimuth position of the target point. P Let x' be the range position of the target point, x′ be the actual azimuth position of the SAR radar, j be the imaginary unit, exp(·) be the exponential function, and c be the speed of light. L represents the distance-space bandwidth, Δf is the signal bandwidth, and L a Where λ is the synthetic aperture length and λ is the wavelength, ΔR(x′-x) P r P ) represents the azimuth spatial variation term in the slant range at point P, and w(·) represents the antenna azimuth window gain.

[0100] This invention utilizes orientation-to-Fourier transform and, through convolution theorem substitution of time and frequency domain terms, employs FFT and complex multiplication to avoid the interference in the H function of the traditional frequency domain response function. trans，P The double integral operation of (x′, η) is performed. Then, by approximating the coupling term of the frequency domain response function of the trajectory deviation track and the ideal straight track interference through the beam center decomposition, and after simplification and integration, H can be obtained. trans，P Efficient modulation method in the hybrid domain of (x′, η):

[0101]

[0102] Where, ψ(x′, rP ) represents the range-varying offset, and δr(x′) represents the scene-invariant track offset. G A (ξ,r P G represents the focusing depth term of the frequency domain response function to interference on an ideal straight-line trajectory. B (η) is the distance space frequency domain window function.

[0103] H can be obtained through equation (3). trans，P The calculation method for (x′, η) consists of two steps: initialization and real-time modulation. Initialization involves rapidly calculating the ideal straight-line trajectory interference frequency domain response function of the deception jamming template in the azimuth frequency domain. Real-time modulation performs flexible real-time trajectory offset compensation in the azimuth time domain, as shown in steps two and three below.

[0104] Step 2: Initialization, calculate the deception template azimuth frequency domain filter H after azimuth focusing and range migration compensation in the azimuth frequency domain. diff (ξ,r P Then, an inverse Fourier transform of the orientation is performed to obtain the initialization template H. ini (x′,r P This step avoids the double integral operation of the SAR system correlation filter in the traditional interference frequency domain response function by using FFT and complex multiplication.

[0105] Step 2.1, perform slant range and phase compensation on the deception template using an ideal straight-line trajectory:

[0106]

[0107] Among them, h P (x P r P () is a deception jamming template with ideal straight-line track slant range phase.

[0108] Step 2.2: Perform azimuth focusing and range migration compensation in the azimuth frequency domain to obtain the azimuth frequency domain expression of the interference frequency domain response function of the ideal straight-line track:

[0109] H diff (ξ,r P ) = G A (ξ,r P FT x (h P (x P r P (5)

[0110] Among them, G A (ξ,r P The focus depth term is represented by the following formula:

[0111]

[0112] Where j is the imaginary unit, ξ is the azimuth spatial frequency, and ξ = 2πf a / v, where f a This represents the azimuth frequency. Ω x For azimuth space bandwidth, R0 is the slant distance from the scene center.

[0113] Step 2.3: Calculate the initialization template H using the inverse Fourier transform in the orientation direction. ini (x′,r P ):

[0114] H ini (x′,r P ) = IFT ξ [H diff (ξ,r P (7)

[0115] Among them, IFT ξ This is the inverse Fourier transform of the azimuth to the frequency domain.

[0116] Step 3: Real-time modulation after the SAR radar enters the interference area, and range-space-variable offset ψ(x′, r) after decomposition of the initial template coupling term in the azimuth time domain. P Compensation is performed on the scene-invariant track offset δr(x′), thereby enabling the construction of a real-time SAR system correlation filter H pulse-by-pulse in the azimuth and time domain. trans，P (x′,η);

[0117] Step 3.1: Real-time detection of SAR track offset vector d(x′) and offset angle β(x′), and calculation of range spatially varying offset ψ(x′, r) at the current SAR position x′. P The calculation formulas for the scene-invariant track offset δr(x′) and the scene-invariant track offset are as follows:

[0118]

[0119]

[0120] Where θ0 is the antenna-down view of the scene center point, and Δr is the ground distance offset from the scene center point to the position of any false point target P in the pre-deception interference area.

[0121] Step 3.2, initialize template H at the current SAR location x′. ini (x′,r P ) Perform distance spatial offset ψ(x′, r P Compensation modulation, constructing the SAR system correlation filter H trans， P(x′,η), its modulation formula is as follows:

[0122]

[0123] Among them, G B (η) is the frequency domain window function of the distance space. This function is used to perform amplitude weighting in the frequency domain of the distance space. Its mathematical expression is:

[0124]

[0125] Step 4: Forwarding the interference signal, and using the real-time SAR system's correlation filter H trans，P (x′, η) and the jammer-related filter H jamfilter Multiplying (X′, η) in the distance frequency domain yields the jammer's frequency domain response function H. jammer，P (x′,η) is convolved with the intercepted SAR signal and then used to forward the non-linear SAR deception jamming signal.

[0126] Step 4.1, apply the correlation filter H of the real-time SAR system. trans，P (x′, η) and the jammer-related filter H jamfilter Multiplying (x′, η) in the distance frequency domain yields the jammer's frequency domain response function H. jammer，P (x′, η), the modulation operation expression is as follows:

[0127] H jammer，P (x′,η)=H trans，P (x′,η)·H jamfilter (x′,η) (12)

[0128] Among them, the jammer-related filter H jamfilter The formula for calculating (x′,η) is as follows:

[0129]

[0130] Where, x J r represents the azimuth position of the jammer. J Let x be the range position of the jammer. J R′ represents the azimuth position of the jammer. J This represents the slant range of the actual non-linear flight path of the jamming aircraft.

[0131] Step 4.2: Perform a frequency domain convolution operation between the intercepted SAR radar transmitted signal and the jammer's frequency domain response function to obtain the forwarding jamming signal.

[0132] S jammer，P (x P r P |x′)=IFT η {FT r [S jammer(x′|x J r J )]·H jammer，P (x′,η)) (14)

[0133] Among them, S jammer，P (x P r P |x′) represents the deception jamming signal targeted by jammer J in the pre-deception jamming area under SAR non-linear trajectory conditions, S jammer (x′|x J r J ) represents the non-linear SAR signal intercepted by jammer J. Where, IFT η For the inverse Fourier transform of the range to the frequency domain, FT r This is the Fourier transform from the distance domain to the time domain.

[0134] To verify the effectiveness of this invention, the following simulation was performed. It is assumed that the SAR radar track has offsets in both the horizontal and vertical tracks, such as... Figure 4 The horizontal track offset function is y(x) = 0.2sin(pi / 200x) + 0.2cos(pi / 600x) + 0.1rand, and the vertical track offset function is y(x) = 0.225sin(pi / 200x) + 0.225cos(pi / 600x) + 0.1rand. The SAR parameters are set as shown in Table 1.

[0135] Table 1

[0136]

[0137] The first set of simulation experiments uses the method of this invention to generate interference signals for a single false point target, where the coordinates of the point target in the simulated deception interference area are P1(x). P r P )=(-1.5km,-1.5km),P2(x) P r P )=(0km,0km),P3(x P r P = (1.5km, 1.5km). Figure 5 , Figure 6a , Figure 6b , Figure 7 , Figure 8a , Figure 8b , Figure 9 , Figure 10a , Figure 10bThe invention presents close-up images, range profiles, and azimuth profiles of point targets after the interference signal is imaged in SAR radar using the method of this invention. The false point targets generated by this invention are compared and analyzed with the real SAR scattering point targets (RS) and SAR point-by-point superposition direct calculation (SA) indicators, including 3dB impulse response width (IRW), peak sidelobe ratio (PSLR), and integral sidelobe ratio (ISLR), as shown in Table 2.

[0138] Table 2

[0139]

[0140]

[0141] The last two columns of Table 2 list the statistical indices for all three scattering points, including the mean and standard deviation (STD). Theoretical and simulation results show that the deceptive jamming signal generated by this invention realistically reproduces the echo characteristics of non-linear SAR radar, and its imaging results can approach the target resolution of the true scattering point of SAR radar even in a large scene interference range.

[0142] The second set of simulation experiments uses the method of this invention to generate a fake scenario, wherein the deception template of the fake scenario is as follows: Figure 11 As shown. Figure 12a , Figure 12b The image shown is a partial image of the jamming signal implemented by the method of this invention after imaging in a SAR radar. It can be seen that the deceptive jamming signal generated by this invention can effectively preserve the deceptive electromagnetic features of the false scene, such as points, lines, surfaces, and brightness, when countering non-linear SAR tracks, achieving a realistic deception effect. We used MATLAB on a computer with 256GB of RAM and an AMD Ryzen Threadripper PRO 5975WX CPU to simulate the aforementioned false scene. We compared the modulation computation efficiency using RS, SA, and EHD methods, and the time consumed by each method is shown in Table 3. It can be found that the EHD method requires the shortest modulation time.

[0143] Table 3

[0144]

[0145] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A SAR deception jamming method of hybrid domain high-efficiency track migration compensation, characterized in that, Comprise the following steps: Step one: after the SAR radar into the jammer reconnaissance range, obtain the relevant parameters of SAR radar, according to the false electromagnetic features produced in SAR image by jamming, build the jammer deception template, including: Step 1.1, reconnaissance need to obtain the relevant parameters of SAR radar, the relevant parameters include the following three kinds: (1) platform parameters, platform flight altitude , platform speed ; (2) Antenna parameters, antenna down-look angle , synthetic aperture length ; (3) signal parameters, signal carrier frequency , signal bandwidth , pulse duration and pulse repetition interval ; After the SAR radar into the reconnaissance range of jammer, the relevant parameters of SAR radar are obtained initially; the ideal straight track of SAR is calculated and estimated through platform parameters and antenna parameters, the jamming frequency domain response function of ideal straight track of SAR is constructed through antenna parameters and signal parameters; when the jamming object is non straight track SAR, the non straight track of SAR is obtained pulse by pulse in real-time modulation stage and the track offset is calculated, which is used for trajectory offset compensation, and the jamming frequency domain response function of SAR actual non straight track is generated; Step 1.2, according to the false electromagnetic features produced in SAR image by jamming, build the jammer deception template; Obtaining pre-interference region slant range plane Equal interval sampling is performed, and according to false electromagnetic characteristics which are to be generated in the SAR image by the jammer, radar backscattering coefficients of false scattering centers at each sampling position are set to obtain a jammer deception template : （1） in, , These represent the range and azimuth positions of the false point target within the pre-interference area, respectively, where m and n are integers representing the index of the false point target in the range and azimuth directions, respectively. For two-dimensional Dirac functions, , These represent the sampling intervals in the range and azimuth directions of the pre-interference region, respectively. The summation symbol; Generation of correlation filters for SAR systems with non-linear trajectories after interception ; direct calculation method of traditional point-by-point superposition The expression is: （2） wherein, represents the distance spatial frequency, is a distance-wise rectangular window function, is a signal pulse width, is an azimuth-wise antenna pattern rectangular window function, is an azimuth-wise position of the target point, is a distance-wise position of the target point, is an actual azimuth-wise position of the SAR radar, denotes an imaginary unit, is an exponential function, is the speed of light, represents the distance spatial bandwidth, is a signal bandwidth, is a synthetic aperture length, is a wavelength, is an azimuth-wise space variant term in the ideal straight line slant range of the P point, is an antenna azimuth window gain; By azimuth Fourier transform, and by convolution theorem substitution of time domain term and frequency domain term, FFT and complex multiplication are adopted to avoid double integral operation in traditional interference frequency domain response function ; and by beam center approximate decomposition, the coupling term of trajectory offset trajectory and ideal straight line trajectory interference frequency domain response function is decomposed, and after integration, the mixed domain efficient modulation method is obtained : （3） wherein, is a range-dependent bias, is a scene-independent track bias is a focusing depth term of the ideal linear track jamming frequency domain response function, is a range-space frequency domain window function; Step two: azimuth focusing and range migration compensation calculation are carried out on the jammer deception template in azimuth frequency domain, and then inverse Fourier transform in azimuth direction is carried out to obtain the initialization template; Step three: the track offset compensation after coupling item decomposition is carried out on the initialization template in azimuth time domain, and the real-time SAR radar parameter related filter is constructed pulse by pulse in azimuth time domain; Step four: the real-time SAR radar parameter related filter and the jammer related filter are multiplied in distance frequency domain, the non straight track jamming frequency domain response function is obtained, the non straight track SAR deception jamming signal is obtained after convolution operation of intercepted SAR radar transmitting signal, and then the signal is forwarded.

2. The SAR deception jamming method of claim 1, wherein The step two comprises azimuth focusing and distance migration compensation after azimuth frequency domain filtering of the deception template Then, inverse azimuth Fourier transform is performed to obtain the initialized template ; Comprise: Step 2.1, the slant range phase compensation of ideal straight track is carried out on the deception template: （4） wherein, is a deception jamming template with ideal straight-line track slant range phase; Step 2.2, azimuth focusing and range migration compensation are carried out in azimuth frequency domain, and the azimuth frequency domain expression of ideal straight track jamming frequency domain response function is obtained: （5） wherein represents the focusing depth term, which is calculated as follows: （6） wherein is the imaginary unit, is the azimuth spatial frequency, wherein is the azimuth frequency; is the azimuth spatial bandwidth, , is the scene center slant range; Step 2.

3. Compute the initial template by an inverse Fourier transform in the orientation direction : （7） wherein is the inverse Fourier transform in the azimuthal frequency domain.

3. The SAR deception jamming method of claim 2, wherein, The step three comprises: real-time modulation after the SAR radar enters the interference area, and the distance direction of the initialized template coupling item is decomposed in the azimuth time domain And the scene invariant track offset Compensation is carried out, so as to construct the real-time SAR system correlation filter pulse by pulse in the azimuth time domain ; comprising: Step 3.1, Real-time detection of SAR track offset vectors and offset angle Calculate the current SAR position Distance at the location of the spatial offset Scene-invariant track offset The calculation formula is as follows: （8） （9） wherein, is the antenna down view angle of the scene center point, is set to the distance from the scene center point to the ground plane offset distance of the arbitrary false point target in the pre-deception jamming region, is set to the distance from the scene center point to the ground plane offset distance of the arbitrary false point target in the pre-deception jamming region, Step 3.2, distance range migration is performed on the initialized template at the current SAR position Step 3.3, the range migration compensated template is modulated to construct the SAR system correlation filter Step 3.4, the SAR system correlation filter is convolved with the range compressed signal to obtain the SAR image Step 3.5, the SAR image is deconvolved with the SAR system correlation filter to obtain the final SAR image The modulation formula is as follows: （10） wherein is a range-space frequency domain window function by which the range-space frequency domain amplitude is weighted, the mathematical expression of which is （11）。 4. The SAR deception jamming method of claim 3, wherein, The step four comprises: multiplying the real-time SAR system correlation filter The jammer correlation filter The jammer frequency domain response function is obtained by multiplying the distance frequency domain After the convolution operation with the intercepted SAR radar transmitting signal, the retransmission of the non-linear track SAR deception jamming signal is carried out. Step 4.1, Real-time SAR system correlation filter Jammer correlation filter Jammer frequency domain response function by multiplying in range frequency domain The modulation operation expression is as follows: （12） wherein the jammer correlation filter The calculation formula is as follows: （13） wherein, the azimuth position of the jammer, the range position of the jammer, the azimuth position of the jammer, the actual non-straight track slant range of the position where the jammer is located; Step 4.2, frequency domain convolution operation is carried out between intercepted SAR signal and jammer frequency domain response function to obtain the forwarding jamming signal: （14） wherein, represent the deception jammer deception jamming signals aiming at the pre-deception jamming region of the represent the deception jammer intercepted non-straight track SAR signals, is the inverse Fourier transform of the frequency domain in the range direction, is the Fourier transform of the time domain in the range direction.

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