SAR deception jamming method and device based on distance and azimuth two-dimensional modulation

Abstract

The invention provides an SAR deception jamming method and device based on distance and azimuth two-dimensional modulation, and relates to the technical field of radar signal processing. The method comprises the following steps: determining an SAR signal intercepted by a jammer according to a transmitting signal of the SAR and an instantaneous slope distance from the jammer to the SAR; an interference signal is determined according to the instantaneous slant range difference between the jammer and the target, the distance offset in the distance direction, the distance offset in the azimuth direction and the SAR signal intercepted by the jammer, and the interference signal comprises an active cancellation signal and a distance and azimuth two-dimensional modulation phase; carrier frequency removal processing is carried out on the echo signal received by the SAR, the echo signal after carrier frequency removal is obtained, and the echo signal received by the SAR is the sum of the interference signal and the target echo signal; and imaging the echo signal after carrier frequency removal by using a distance Doppler algorithm to obtain an echo signal after imaging processing, so that diversified interference effects can be achieved.

Description

Technical Field

[0001] The present invention relates to the field of radar signal processing technology, and in particular to a SAR deception jamming method and device based on range-azimuth two-dimensional modulation. Background Art

[0002] Synthetic Aperture Radar (SAR) has the advantages of working all day and all weather and having strong information acquisition capabilities, so it has extremely important application value in the field of earth observation and reconnaissance and surveillance. In order to protect targets from illegal detection and reconnaissance, implementing effective deception jamming on SAR reconnaissance systems has always been a research hotspot in the field of electronic countermeasures. Deception jamming technology generates false targets in the imaging results by radiating electromagnetic waves similar to the target echo, affecting the SAR reconnaissance system's recognition of the real target and weakening its ability to obtain information.

[0003] At present, the satellite-borne SAR scattered wave deception jamming method based on frequency diversity array is used. By introducing a small frequency increment and an additional range dimension degree of freedom in the carrier frequency of adjacent array elements, multiple false targets in the range dimension are generated, and their positions are determined by the frequency deviation. However, in this method, the real target is not hidden, and the frequency diversity array is used to interfere with the intercepted SAR signal in the range dimension. The jamming effect is relatively simple, making the false target easy to be identified by SAR. Summary of the invention

[0004] The purpose of the embodiments of the present invention is to provide a SAR deception jamming method and device based on range-azimuth two-dimensional modulation, so as to solve the problem that the jamming effect is relatively single, making it easy for false targets to be identified by SAR.

[0005] To solve the above technical problems, the embodiments of the present invention provide the following technical solutions:

[0006] A first aspect of the present invention provides a SAR deception jamming method based on range-azimuth two-dimensional modulation, and the SAR deception jamming method based on range-azimuth two-dimensional modulation includes:

[0007] Determine the SAR signal intercepted by the jammer based on the SAR transmission signal and the instantaneous slant range from the jammer to the SAR;

[0008] According to the instantaneous slant range difference between the jammer and the target, the range offset in the range direction, the range offset in the azimuth direction and the SAR signal intercepted by the jammer, the jamming signal is determined, and the jamming signal includes an active cancellation signal and a two-dimensional modulation phase of the range and azimuth;

[0009] Perform carrier frequency removal processing on the echo signal received by the SAR to obtain the echo signal after carrier frequency removal. The echo signal received by the SAR is the sum of the interference signal and the target echo signal;

[0010] The range Doppler algorithm is used to perform imaging processing on the echo signal after the carrier frequency is removed to obtain the echo signal after imaging processing. The echo signal after imaging processing is used to generate multiple false targets.

[0011] A second aspect of the present invention provides a SAR deception jamming device based on range-azimuth two-dimensional modulation, and the SAR deception jamming device based on range-azimuth two-dimensional modulation includes:

[0012] A first determination module is used to determine the SAR signal intercepted by the jammer according to the SAR transmission signal and the instantaneous slant range from the jammer to the SAR;

[0013] The second determination module is used to determine the interference signal according to the instantaneous slant range difference between the jammer and the target, the range offset in the range direction, the range offset in the azimuth direction and the SAR signal, where the interference signal includes an active cancellation signal and a range-azimuth two-dimensional modulation phase;

[0014] The carrier removal processing module is used to perform carrier removal processing on the echo signal received by the SAR to obtain the echo signal after the carrier is removed. The echo signal received by the SAR is the sum of the interference signal and the target echo signal;

[0015] The imaging processing module is used to perform imaging processing on the echo signal after carrier frequency removal by using the range Doppler algorithm to obtain the echo signal after imaging processing. The echo signal after imaging processing is used to generate multiple false targets.

[0016] Compared with the prior art, the SAR deception jamming method and device based on range-azimuth two-dimensional modulation provided by the present invention determines the SAR signal intercepted by the jammer according to the SAR transmission signal and the instantaneous slant range from the jammer to the SAR; determines the interference signal according to the instantaneous slant range difference between the jammer and the target, the range offset in the range direction, the range offset in the azimuth direction and the SAR signal intercepted by the jammer, and the interference signal includes an active cancellation signal and a range-azimuth two-dimensional modulation phase; performs carrier frequency removal processing on the echo signal received by the SAR to obtain a carrier frequency-removed echo signal, and the echo signal received by the SAR is the sum of the interference signal and the target echo signal; uses the range Doppler algorithm to perform imaging processing on the carrier frequency-removed echo signal to obtain an imaging-processed echo signal, and the imaging-processed echo signal is used to indicate the generation of multiple false targets. In this way, the two-dimensional modulation phase of range and azimuth is introduced, so that the echo signal finally obtained after imaging processing is used to generate multiple false targets in the range dimension and azimuth dimension. The positions of multiple false targets can be flexibly changed and accurately controlled to achieve diversified interference effects. In addition, the echo signal received by the SAR is the sum of the interference signal and the target echo signal, which can realize active cancellation of the target echo signal and hide the real target on the SAR image, making it difficult for the SAR reconnaissance system to identify the real target from multiple false targets. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] By reading the detailed description below with reference to the accompanying drawings, the above and other objects, features and advantages of the exemplary embodiments of the present invention will become readily understood. In the accompanying drawings, several embodiments of the present invention are shown in an exemplary and non-limiting manner, and the same or corresponding reference numerals represent the same or corresponding parts, wherein:

[0018] Figure 1 The geometric model of SAR deception jamming is schematically shown;

[0019] Figure 2 The flowchart of the SAR deception jamming method based on range-azimuth two-dimensional modulation is schematically shown;

[0020] Figure 3 A schematic diagram of target imaging results is schematically shown;

[0021] Figure 4 The interference imaging result in the case of 6 array elements is schematically shown;

[0022] Figure 5 The interference imaging result in the case of 9 array elements is schematically shown;

[0023] Figure 6 The structure of a SAR deception jammer based on range-azimuth two-dimensional modulation is schematically shown. DETAILED DESCRIPTION

[0024] The exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided in order to enable a more thorough understanding of the present invention and to fully convey the scope of the present invention to those skilled in the art.

[0025] It should be noted that, unless otherwise specified, the technical terms or scientific terms used in the present invention should have the common meanings understood by those skilled in the art to which the present invention belongs.

[0026] The method in the embodiment of the present invention is described in detail below.

[0027] Figure 1 The geometric model of SAR deception jamming is schematically shown. The geometric model includes a SAR platform and a jammer. The SAR platform moves at a uniform speed V along the y-axis direction and the height is H. According to the geometric model of SAR deception jamming, the instantaneous slant range from the jammer to the SAR is determined to be R. J (t a), the instantaneous slant range from the target to the SAR is R P (t a ), the jammer uses a uniform linear array composed of M transmitting antennas (transmitting array elements), the spacing between the transmitting array elements is d, the target viewing angle is θ, M is the number of transmitting array elements, b m (m=1,2,…,M) is the range-azimuth two-dimensional modulation phase of the mth transmitting array element, and Txm(m=1,2,…,M) is the mth transmitting array element.

[0028] Figure 2 The flowchart of the SAR deception jamming method based on range and azimuth two-dimensional modulation in the embodiment of the present invention is schematically shown. Figure 2 As shown, the method may include:

[0029] S201. Determine the SAR signal intercepted by the jammer according to the SAR transmission signal and the instantaneous slant range from the jammer to the SAR.

[0030] Before determining the SAR signal intercepted by the jammer according to the SAR transmission signal and the instantaneous slant range from the jammer to the SAR, the method further includes:

[0031] The instantaneous slant range difference between the jammer and the target is determined based on the instantaneous slant range from the jammer to the SAR and the instantaneous slant range from the target to the SAR.

[0032] The expression of the instantaneous slant range difference between the jammer and the target is:

[0033] ΔR(t a )=R p (t a )-R J (t a );

[0034] Among them, ΔR(t a ) is the instantaneous slant range difference between the jammer and the target, R J (t a ) is the instantaneous slant range from the jammer to the SAR, Rp(ta) is the instantaneous slant range from the target to the SAR, t a For slow time.

[0035] In addition, considering that the jammer uses a uniform linear array composed of M transmitting antennas, the array element spacing is d, the target viewing angle is θ, and the instantaneous slant range R from the mth transmitting array element to the SAR is established: jm (t a ) is: R jm (t a )=R J (t a )-(m-1)dsinθ.

[0036] The reconnaissance receiver receives the SAR transmission signals s(t r ,t a ), s(t r ,t a ) is expressed as:

[0037]

[0038] Among them, t r For fast time, t r For fast time, T a is the synthetic aperture time, T p is the distance pulse width, f0 is the carrier frequency, K r is the range modulation frequency, and rect(·) is the rectangular window function.

[0039] Specifically, considering the distance history of the signal in the propagation process, the SAR signal J intercepted by the jammer is determined according to the SAR transmission signal and the instantaneous slant range from the jammer to the SAR. r (t r ,t a ) is:

[0040]

[0041] Among them, s(t r ,t a ) is the SAR transmission signal, δ is the impulse function, R J (t a ) is the instantaneous slant distance from the jammer to the SAR, c is the speed of light, t r For fast time, t a For slow time.

[0042] S202: Determine a jamming signal according to the instantaneous slant range difference between the jammer and the target, the range offset in the range direction, the range offset in the azimuth direction, and the SAR signal intercepted by the jammer.

[0043] The interference signal includes an active cancellation signal and a range-azimuth two-dimensional modulation phase.

[0044] Specifically, the jammer signal is determined based on the instantaneous slant range difference between the jammer and the target, the range offset in the range direction, the range offset in the azimuth direction, and the SAR signal intercepted by the jammer, including:

[0045] Step A1: According to the instantaneous slant range difference between the jammer and the target, the SAR signal intercepted by the jammer is delayed to obtain a delayed SAR signal.

[0046] Specifically, the expression of the delayed SAR signal is:

[0047]

[0048] Among them, J1(t r ,t a ) is the delayed SAR signal, J r (t r ,t a ) is the SAR signal intercepted by the jammer, t r For fast time, t a is the slow time, δ is the impulse function, ΔR(t a ) is the instantaneous slant range difference between the jammer and the target, c is the speed of light, R J (t a ) is the instantaneous slant range from the jammer to the SAR, T a is the synthetic aperture time, f0 is the carrier frequency, K r The frequency is modulated in the distance direction.

[0049] The range-azimuth two-dimensional modulation of the SAR signal intercepted by the jammer refers to the range modulation and azimuth modulation of the SAR signal.

[0050] Step A2: construct an active cancellation signal according to the delayed SAR signal.

[0051] Specifically, the expression of the active cancellation signal is:

[0052] S c (t r ,t a )=-J1(t r ,t a );

[0053] Among them, Sc(tr,ta) is the active cancellation signal, J1(tr,ta) is the delayed SAR signal, t r For fast time, t a For slow time.

[0054] The active cancellation signal is a cancellation signal with the same amplitude, delay and frequency as the target echo signal, but opposite phase.

[0055] Step A3: construct the range-azimuth two-dimensional modulation phase of the mth transmitting array element according to the range offset in the range direction and the range offset in the azimuth direction.

[0056] Specifically, by introducing the range-azimuth two-dimensional modulation phase between adjacent transmitting array elements, the range-azimuth two-dimensional modulation phase of the mth transmitting array element is expressed as:

[0057]

[0058] Among them, b m(t r ,t a ) is the distance-azimuth two-dimensional modulation phase of the mth transmitting array element, K r is the range modulation frequency, γ x,m is the distance bias of the mth transmitting array element, c is the speed of light, t r For fast time, R J (t a ) is the instantaneous slant distance from the jammer to the SAR, ΔR(t a ) is the instantaneous slant range difference between the jammer and the target, K a is the Doppler modulation frequency, γ y,m is the azimuth range offset of the mth transmitting array element, V is the flight speed of SAR, t a For slow time.

[0059] The range-azimuth two-dimensional modulation phase of the mth transmitting array element is a phase including a range offset in the range direction and a range offset in the azimuth direction.

[0060] Step A4: Determine the interference signal according to the delayed SAR signal, the active cancellation signal and the range-azimuth two-dimensional modulation phase of the mth transmitting array element.

[0061] Specifically, the expression of the interference signal is:

[0062]

[0063] Among them, J2(tr,ta) is the interference signal, J1(tr,ta) is the delayed SAR signal, t r For fast time, t a is slow time, b m (t r ,t a ) is the range-azimuth two-dimensional modulation phase of the mth transmitting array element, S c (t r ,t a ) is the active cancellation signal, M is the number of transmitting array elements, R J (t a ) is the instantaneous slant distance from the jammer to the SAR, ΔR(t a ) is the instantaneous slant range difference between the jammer and the target, c is the speed of light, f0 is the carrier frequency, T p is the distance pulse width, T a is the synthetic aperture time, K r is the range modulation frequency, γ x,m is the distance bias of the mth transmitting array element, γ y,m is the azimuth distance offset of the mth transmitting array element, K a is the Doppler modulation frequency, and V is the flight speed of SAR.

[0064] After determining the interference signal according to the delayed SAR signal, the active cancellation signal and the range-azimuth two-dimensional modulation phase of the mth transmitting array element, the method further includes:

[0065] According to the instantaneous slant range R from the target to the SAR p (t a ), determine the target echo signal as:

[0066]

[0067] Among them, S p (t r ,t a ) is the target echo signal, m is the mth transmitting array element, M is the number of transmitting array elements, t r For fast time, t a is the slow time, R p (t a ) is the instantaneous slant distance from the target to the SAR, T p is the distance pulse width, T a is the synthetic aperture time, f0 is the carrier frequency, c is the speed of light, K r is the range modulation frequency, γ x,m is the distance bias of the mth transmitting array element, γ y,m is the azimuth distance offset of the mth transmitting array element, K a is the Doppler modulation frequency, and V is the flight speed of SAR.

[0068] S203: Perform carrier frequency removal processing on the echo signal received by the SAR to obtain a carrier frequency removed echo signal.

[0069] Among them, the echo signal received by SAR is the sum of the interference signal and the target echo signal.

[0070] In order to obtain the baseband signal, it is necessary to remove the carrier frequency of the echo signal received by the SAR to obtain the echo signal after the carrier frequency is removed. J (t r ,t a ) is:

[0071]

[0072] Among them, J2(t r ,t a ) is the interference signal, S p (t r ,t a ) is the target echo signal, m is the mth transmitting array element, M is the number of transmitting array elements, t r For fast time, ta is the slow time, T p is the distance pulse width, T a is the synthetic aperture time, f0 is the carrier frequency, c is the speed of light, K r is the range modulation frequency, γ x,m is the distance bias of the mth transmitting array element, γ y,m is the azimuth distance offset of the mth transmitting array element, K a is the Doppler modulation frequency, V is the flight speed of SAR, R m (t a ) is the equivalent instantaneous slant range from the false target to the SAR, R m (t a )=R J (t a )+R jm (t a )+2ΔR(t a ), R J (t a ) is the instantaneous slant distance from the jammer to the SAR, ΔR(t a ) is the instantaneous slant range difference between the jammer and the target, R jm (t a ) is the instantaneous slant range from the mth transmitting array element to the SAR.

[0073] S204 , using a range Doppler algorithm, performing imaging processing on the echo signal after the carrier frequency is removed to obtain an echo signal after imaging processing.

[0074] The echo signal after imaging processing is used to indicate the generation of multiple false targets.

[0075] Specifically, the range Doppler algorithm is used to perform imaging processing on the echo signal after the carrier frequency is removed to obtain the echo signal after imaging processing, including:

[0076] Step B1: Using Fourier transform, transform the carrier-removed echo signal into the range frequency domain to obtain a range frequency domain echo signal.

[0077] The expression of the range frequency domain echo signal is:

[0078]

[0079] Among them, y J (tr,ta) is the echo signal after removing the carrier frequency, f r is the distance frequency, t r is the fast time, m is the mth transmitting array element, M is the number of transmitting array elements, K r is the range modulation frequency, γ x,m is the distance bias of the mth transmitting array element, γy,m is the azimuth distance offset of the mth transmitting array element, c is the speed of light, t a is the slow time, T a is the synthetic aperture time, f0 is the carrier frequency, R m (t a ) is the equivalent instantaneous slant range from the false target to the SAR, K a is the Doppler modulation frequency, V is the flight speed of SAR, B r is the distance bandwidth, B r =K r T p , T p is the distance pulse width.

[0080] Step B2: Determine the echo signal after frequency domain range compression according to the range frequency domain echo signal and the range matched filter reference function.

[0081] Specifically, construct the distance matched filter reference function H r (f r )=exp(jπf r 2 K r ), multiply the distance frequency domain echo signal and the distance matched filter reference function to obtain the echo signal after frequency domain distance compression, the echo signal after frequency domain distance compression y J,rc (f r ,t a ) is:

[0082]

[0083] Where m is the mth transmitting array element, M is the number of transmitting array elements, and f r is the distance frequency, K r is the distance modulation frequency, c is the speed of light, γ x,m is the distance bias of the mth transmitting array element, γ y,m is the azimuth distance offset of the mth transmitting array element, t a is the slow time, T a is the synthetic aperture time, f0 is the carrier frequency, Rm(ta) is the equivalent instantaneous slant range from the false target to the SAR, K a is the Doppler modulation frequency, and V is the flight speed of SAR.

[0084] Step B3: Perform inverse Fourier transform on the echo signal after frequency domain distance compression to obtain the echo signal after time domain distance compression.

[0085] Echo signal y after time domain distance compression J,rc (t r ,t a ) is:

[0086]

[0087] Among them, y J , rc(fr,ta) is the echo signal after frequency domain distance compression, f r is the distance frequency, t r For fast time, B r is the range bandwidth, Br = KrTp, Tp is the range pulse width, Rm(ta) is the equivalent instantaneous slant range from the false target to the SAR, c is the speed of light, γ x,m is the distance bias of the mth transmitting array element, γ y,m is the azimuth distance offset of the mth transmitting array element, T a is the synthetic aperture time, f0 is the carrier frequency, K r is the range modulation frequency, K a is the Doppler modulation frequency, and V is the flight speed of SAR.

[0088] Step B4: Perform azimuth Fourier transform on the echo signal after time-domain range compression to obtain an azimuth frequency-domain echo signal.

[0089] Azimuth frequency domain echo signal y J,rc (t r ,f a ) is:

[0090]

[0091] Among them, y J , rc(tr,ta) is the echo signal after time domain distance compression, f a is the azimuth frequency, B r is the distance bandwidth, B r =K r T p , T p is the distance pulse width, R m (t a ) is the equivalent instantaneous slant range from the false target to the SAR, c is the speed of light, γ x,m is the distance bias of the mth transmitting array element, γ y,m is the azimuth distance offset of the mth transmitting array element, x p is the target’s azimuth position, V is the SAR’s flight speed, T a is the synthetic aperture time, f0 is the carrier frequency, R P0 is the shortest slant distance from the target to the SAR, d is the array element spacing, θ is the target viewing angle, K a Tune frequency for Doppler.

[0092] Step B5: multiply the azimuth frequency domain echo signal, the azimuth matched filter reference function and the range migration correction phase function, and perform azimuth inverse Fourier transform on the multiplied echo signal to obtain the echo signal after imaging processing.

[0093] Specifically, construct the azimuth matched filter reference function and the range migration correction phase function The azimuth frequency domain echo signal y J,rc (t r ,f a ), azimuth matched filter reference function H a (f a ) and the range migration correction phase function H rcmc (f r ) and perform azimuth inverse Fourier transform on the echo signal after multiplication to obtain the echo signal after imaging processing. The expression of the echo signal after imaging processing is:

[0094]

[0095] Among them, y J,rcmc (t r ,t a ) is the echo signal after imaging processing, y J,rc (t r ,f a ) is the azimuth frequency domain echo signal, H a (f a ) is the azimuth matched filter reference function, H rcmc (f r ) is the range migration correction phase function, t r For fast time, f a is the azimuth frequency, f r is the distance frequency, B r =K r T p , B r is the distance bandwidth, B a is the Doppler bandwidth, R P0 is the shortest slant distance from the target to the SAR, c is the speed of light, γ x,m is the distance offset of the mth transmitting array element, t a is the slow time, x p is the target’s position, γ y,m is the azimuth distance offset of the mth transmitting array element, V is the flight speed of SAR, f0 is the carrier frequency, m is the mth transmitting array element, d is the transmitting array element spacing, K a is the Doppler modulation frequency, K r The frequency is modulated in the distance direction.

[0096] The echo signal after imaging processing generates multiple false targets in the range dimension and azimuth dimension. The number of multiple false targets is related to the number of array elements. The positions of multiple false targets are offset from range to range γ. x,m and the azimuth range bias γ y,m Decide.

[0097] The system parameters of the simulation of the present invention are set as follows: the flight altitude of the SAR platform is 10 km, the speed is 250 m / s, the operating carrier frequency is 9.4 GHz, the pulse repetition frequency is 500 Hz, the pulse width is 10 μs, the range bandwidth is 100 MHz, the scene center slant range is 30 km, and the array element spacing is 0.016 m.

[0098] Figure 3 The target imaging result diagram is schematically shown, with the horizontal axis being the distance direction and the vertical axis being the azimuth direction, and the target being located at the center of the scene. Figure 4 The interference imaging result under the condition of 6 array elements is schematically shown, that is, the interference imaging result corresponding to the echo signal after imaging processing under the condition of 6 array elements, where [γ y,1 ,γ y,2 ,γ y,3 ,γ y,4 ,γ y,5 ,γ y,6 ]=[-30,30,-20,20,-10,10]m,[γ x,1 ,γ x,2 ,γ x,3 ,γ x,4 ,γ x,5 ,γ x,6 ]=[-40,40,-80,80,-160,160]m, γ y,m is the azimuth distance offset of the mth transmitting array element, γ x,m is the distance offset of the m-th transmitting array element, where m=1,2,…,M, m is the m-th transmitting array element, and M=6 is the number of transmitting antennas. Figure 5 The interference imaging result under the condition of 9 array elements is schematically shown, that is, the interference imaging result corresponding to the echo signal after imaging processing under the condition of 9 array elements, the horizontal axis is the range direction, the vertical axis is the azimuth direction, [γ y,1 ,γ y,2 ,γ y,3 ,γ y,4 ,γ y,5 ,γ y,6 ,γ y,7 ,γ y,8 ,γ y,9 ]=[40,20,0,-20,-40,-20,0,20,40]m,[γ x,1 ,γ x,2 ,γx,3 ,γ x,4 ,γ x,5 ,γ x,6 ,γ x,7 ,γ x,8 ,γ x,9 ]=[-320,-240,-160,-80,0,80,160,240,320]m, see Figures 3 to 5 , it can be seen that the real target is eliminated, the number of false targets is related to the number of array elements, and the distance of the mth transmitting array element is offset to the distance γ x,m and the azimuth range bias γ y,m The distance position and azimuth position of each false target in the SAR image are determined.

[0099] Based on the above Figure 1 It can be seen from the implementation method that the embodiment of the present invention determines the SAR signal intercepted by the jammer according to the SAR transmission signal and the instantaneous slant range from the jammer to the SAR; determines the interference signal according to the instantaneous slant range difference between the jammer and the target, the range offset in the range direction, the range offset in the azimuth direction and the SAR signal intercepted by the jammer, and the interference signal includes an active cancellation signal and a range-azimuth two-dimensional modulation phase; performs carrier removal processing on the echo signal received by the SAR to obtain a carrier-removed echo signal; uses the range Doppler algorithm to perform imaging processing on the carrier-removed echo signal to obtain an imaging-processed echo signal, and the imaging-processed echo signal is used to indicate the generation of multiple false targets. In this way, two-dimensional modulation of range and azimuth is introduced, so that the echo signal finally obtained after imaging processing is used to generate multiple false targets in the range dimension and azimuth dimension. The positions of multiple false targets can be flexibly changed and accurately controlled to achieve diversified interference effects. In addition, the echo signal received by the SAR is the sum of the interference signal and the target echo signal, which can realize active cancellation of the target echo signal and hide the real target on the SAR image, making it difficult for the SAR reconnaissance system to identify the real target from multiple false targets.

[0100] Based on the same inventive concept, as an implementation of the above-mentioned SAR deception jamming method based on range-azimuth two-dimensional modulation, an embodiment of the present invention further provides a SAR deception jamming device based on range-azimuth two-dimensional modulation. Figure 6 is a structural diagram of the device in the embodiment of the present invention, see Figure 6 As shown, the device may include:

[0101] A first determination module 601 is used to determine the SAR signal intercepted by the jammer according to the SAR transmission signal and the instantaneous slant range from the jammer to the SAR;

[0102] The second determination module 602 is used to determine the interference signal according to the instantaneous slant range difference between the jammer and the target, the range offset in the range direction, the range offset in the azimuth direction and the SAR signal intercepted by the jammer, where the interference signal includes an active cancellation signal and a range-azimuth two-dimensional modulation phase;

[0103] The carrier removal processing module 603 is used to perform carrier removal processing on the echo signal received by the SAR to obtain the echo signal after the carrier is removed. The echo signal received by the SAR is the sum of the interference signal and the target echo signal;

[0104] The imaging processing module 604 is used to perform imaging processing on the carrier-removed echo signal using a range Doppler algorithm to obtain an imaging-processed echo signal, and the imaging-processed echo signal is used to generate multiple false targets.

[0105] The device also includes: a third determination module, which is used to determine the instantaneous slant range difference between the jammer and the target according to the instantaneous slant range from the jammer to the SAR and the instantaneous slant range from the target to the SAR before determining the SAR signal intercepted by the jammer according to the SAR transmission signal and the instantaneous slant range from the jammer to the SAR.

[0106] The second determination module 602 is specifically used to delay the SAR signal intercepted by the jammer according to the instantaneous slant range difference between the jammer and the target to obtain the delayed SAR signal; construct an active cancellation signal according to the delayed SAR signal; construct the range-azimuth two-dimensional modulation phase of the mth transmitting array element according to the range offset in the range direction and the range offset in the azimuth direction; and determine the interference signal according to the delayed SAR signal, the active cancellation signal and the range-azimuth two-dimensional modulation phase of the mth transmitting array element.

[0107] In the second determination module 602, the expression of the delayed SAR signal is:

[0108]

[0109] Among them, J1(tr,ta) is the delayed SAR signal, Jr(tr,ta) is the SAR signal, t r For fast time, t a is the slow time, δ is the impulse function, ΔR(t a ) is the instantaneous slant range difference between the jammer and the target, c is the speed of light, R J (t a ) is the instantaneous slant range from the jammer to the SAR, T a is the synthetic aperture time, f0 is the carrier frequency, K r The frequency is modulated in the distance direction.

[0110] In the second determination module 602, the expression of the active cancellation signal is:

[0111] S c (t r ,t a )=-J1(t r ,t a );

[0112] Among them, Sc(tr,ta) is the active cancellation signal, J1(tr,ta) is the delayed SAR signal, t r For fast time, t a For slow time.

[0113] In the second determination module 602, the expression of the two-dimensional modulation phase of the transmitting array element distance azimuth is:

[0114]

[0115] Among them, b m (t r ,t a ) is the two-dimensional modulation phase of the mth transmitting array element in range and azimuth, K r is the range modulation frequency, γ x,m is the distance bias of the mth transmitting array element, c is the speed of light, t r For fast time, R J (t a ) is the instantaneous slant distance from the jammer to the SAR, ΔR(t a ) is the instantaneous slant range difference between the jammer and the target, K a is the Doppler modulation frequency, γ y,m is the azimuth range offset of the mth transmitting array element, V is the flight speed of SAR, t a For slow time.

[0116] In the second determination module 602, the expression of the interference signal is:

[0117]

[0118] Among them, J2(tr,ta) is the interference signal, J1(tr,ta) is the delayed SAR signal, t r For fast time, t a is slow time, b m (t r ,t a ) is the range-azimuth two-dimensional modulation phase of the mth transmitting array element, S c (t r ,t a ) is the active cancellation signal, M is the number of transmitting array elements, R J (t a ) is the instantaneous slant distance from the jammer to the SAR, ΔR(ta ) is the instantaneous slant range difference between the jammer and the target, c is the speed of light, f0 is the carrier frequency, T p is the distance pulse width, T a is the synthetic aperture time, K r is the range modulation frequency, γ x,m is the distance bias of the mth transmitting array element, γ y,m is the azimuth distance offset of the mth transmitting array element, K a is the Doppler modulation frequency, and V is the flight speed of SAR.

[0119] The imaging processing module 604 is specifically used to transform the carrier-removed echo signal into the range frequency domain by using Fourier transform to obtain the range frequency domain echo signal; determine the echo signal after frequency domain range compression according to the range frequency domain echo signal and the range matching filter reference function; perform inverse Fourier transform on the echo signal after frequency domain range compression to obtain the echo signal after time domain range compression; perform azimuth Fourier transform on the echo signal after time domain range compression to obtain the azimuth frequency domain echo signal; multiply the azimuth frequency domain echo signal, the azimuth matching filter reference function and the range migration correction phase function, and perform azimuth inverse Fourier transform on the multiplied echo signal to obtain the echo signal after imaging processing.

[0120] Imaging processing module 604, the expression of the echo signal after imaging processing is:

[0121]

[0122] Among them, y J,rcmc (t r ,t a ) is the echo signal after imaging processing, y J,rc (t r ,f a ) is the azimuth frequency domain echo signal, H a (f a ) is the azimuth matched filter reference function, H rcmc (f r ) is the range migration correction phase function, t r For fast time, f a is the azimuth frequency, f r is the distance frequency, B r =K r T p , B r is the distance bandwidth, B a is the Doppler bandwidth, R P0 is the shortest slant distance from the target to the SAR, c is the speed of light, γ x,m is the distance offset of the mth transmitting array element, t ais the slow time, x p is the target’s position, γ y,m is the azimuth distance offset of the mth transmitting array element, V is the flight speed of SAR, f0 is the carrier frequency, m is the mth transmitting array element, d is the transmitting array element spacing, K a is the Doppler modulation frequency, K r The frequency is modulated in the distance direction.

[0123] It should be pointed out here that: the above description of the embodiment of the SAR deception jamming device based on range-azimuth two-dimensional modulation is similar to the description of the embodiment of the SAR deception jamming method based on range-azimuth two-dimensional modulation, and has similar beneficial effects as the embodiment of the SAR deception jamming method based on range-azimuth two-dimensional modulation. For technical details not disclosed in the embodiment of the SAR deception jamming device based on range-azimuth two-dimensional modulation of the embodiment of the present invention, please refer to the description of the embodiment of the SAR deception jamming method based on range-azimuth two-dimensional modulation of the present invention for understanding.

[0124] The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art who is familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A SAR deception jamming method based on range-azimuth two-dimensional modulation, characterized in that: The SAR deception jamming method based on range-azimuth two-dimensional modulation includes: Determine the SAR signal intercepted by the jammer based on the SAR transmission signal and the instantaneous slant range from the jammer to the SAR; Determine an interference signal according to the instantaneous slant range difference between the jammer and the target, the range offset in the range direction, the range offset in the azimuth direction, and the SAR signal intercepted by the jammer, wherein the interference signal includes an active cancellation signal and a range-azimuth two-dimensional modulation phase; Performing carrier frequency removal processing on the echo signal received by the SAR to obtain a carrier frequency removed echo signal, wherein the echo signal received by the SAR is the sum of the interference signal and the target echo signal; The range Doppler algorithm is used to perform imaging processing on the carrier-removed echo signal to obtain an imaging-processed echo signal, and the imaging-processed echo signal is used to indicate the generation of multiple false targets.

2. The SAR deception jamming method based on range-azimuth two-dimensional modulation according to claim 1 is characterized in that: Before determining the SAR signal intercepted by the jammer according to the SAR transmission signal and the instantaneous slant range from the jammer to the SAR, the method further includes: The instantaneous slant range difference between the jammer and the target is determined according to the instantaneous slant range from the jammer to the SAR and the instantaneous slant range from the target to the SAR.

3. The SAR deception jamming method based on range-azimuth two-dimensional modulation according to claim 2 is characterized in that: Determining the interference signal according to the instantaneous slant range difference between the jammer and the target, the range offset in the range direction, the range offset in the azimuth direction, and the SAR signal intercepted by the jammer includes: According to the instantaneous slant range difference between the jammer and the target, delay processing is performed on the SAR signal intercepted by the jammer to obtain a delayed SAR signal; Constructing the active cancellation signal according to the delayed SAR signal; Constructing a range-azimuth two-dimensional modulation phase of the mth transmitting array element according to the range offset in the range direction and the range offset in the azimuth direction; The interference signal is determined according to the delayed SAR signal, the active cancellation signal and the range-azimuth two-dimensional modulation phase of the mth transmitting array element.

4. The SAR deception jamming method based on range-azimuth two-dimensional modulation according to claim 3 is characterized in that: The expression of the delayed SAR signal is: Among them, J1(t r ,t a ) is the delayed SAR signal, J r (t r ,t a ) is the SAR signal intercepted by the jammer, t r For fast time, t a is the slow time, δ is the impulse function, ΔR(t a ) is the instantaneous slant range difference between the jammer and the target, c is the speed of light, R J (t a ) is the instantaneous slant distance from the jammer to the SAR, T a is the synthetic aperture time, f0 is the carrier frequency, K r The frequency is modulated in the distance direction.

5. The SAR deception jamming method based on range-azimuth two-dimensional modulation according to claim 4 is characterized in that: The expression of the active cancellation signal is: S c (t r ,t a )=-J1(t r ,t a ); Among them, S c (t r ,t a ) is the active cancellation signal, J1(t r ,t a ) is the delayed SAR signal, t r is the fast time, t a This is the slow time.

6. The SAR deception jamming method based on range-azimuth two-dimensional modulation according to claim 3 is characterized in that: The expression of the range-azimuth two-dimensional modulation phase of the mth transmitting array element is: Among them, b m (t r ,t a ) is the distance-azimuth two-dimensional modulation phase of the mth transmitting array element, K r is the range modulation frequency, γ x,m is the distance offset of the mth transmitting array element, c is the speed of light, t r For fast time, R J (t a ) is the instantaneous slant distance from the jammer to the SAR, ΔR(t a ) is the instantaneous slant range difference between the jammer and the target, K a is the Doppler modulation frequency, γ y,m is the azimuth distance offset of the mth transmitting array element, V is the flight speed of the SAR, t a For slow time.

7. The SAR deception jamming method based on range-azimuth two-dimensional modulation according to claim 3 is characterized in that: The expression of the interference signal is: Wherein, J2(tr,ta) is the interference signal, J1(tr,ta) is the delayed SAR signal, t r For fast time, t a is slow time, b m (t r ,t a ) is the range-azimuth two-dimensional modulation phase of the mth transmitting array element, S c (t r ,t a ) is the active cancellation signal, M is the number of transmitting array elements, R J (t a ) is the instantaneous slant distance from the jammer to the SAR, ΔR(t a ) is the instantaneous slant range difference between the jammer and the target, c is the speed of light, f0 is the carrier frequency, T p is the distance pulse width, T a is the synthetic aperture time, K r is the range modulation frequency, γ x,m is the distance offset of the mth transmitting array element, γ y,m is the azimuth distance offset of the mth transmitting array element, K a is the Doppler modulation frequency, and V is the flight speed of SAR.

8. The SAR deception jamming method based on range-azimuth two-dimensional modulation according to claim 1 is characterized in that: The method of performing imaging processing on the echo signal after carrier frequency removal by using a range Doppler algorithm to obtain the echo signal after imaging processing includes: Using Fourier transform, the carrier-removed echo signal is transformed into a range frequency domain to obtain a range frequency domain echo signal; Determine the echo signal after frequency domain range compression according to the range frequency domain echo signal and the range matched filter reference function; Performing inverse Fourier transform on the echo signal after frequency domain distance compression to obtain an echo signal after time domain distance compression; Performing azimuth Fourier transform on the echo signal after time-domain distance compression to obtain an azimuth frequency-domain echo signal; The azimuth frequency domain echo signal, the azimuth matched filter reference function and the range migration correction phase function are multiplied, and the multiplied echo signal is subjected to azimuth inverse Fourier transform to obtain the echo signal after imaging processing.

9. The SAR deception jamming method based on range-azimuth two-dimensional modulation according to claim 8 is characterized in that: The expression of the echo signal after the imaging process is: Among them, y J,rcmc (t r ,t a ) is the echo signal after the imaging process, y J,rc (t r ,f a ) is the azimuth frequency domain echo signal, H a (f a ) is the azimuth matched filter reference function, H rcmc (f r ) is the range migration correction phase function, t r For fast time, f a is the azimuth frequency, f r is the distance frequency, B r =K r T p , B r is the distance bandwidth, B a is the Doppler bandwidth, R P0 is the shortest slant distance from the target to the SAR, c is the speed of light, γ x,m is the distance offset of the mth transmitting array element, t a is the slow time, x p is the target’s position, γ y,m is the azimuth distance offset of the mth transmitting array element, V is the flight speed of SAR, f0 is the carrier frequency, m is the mth transmitting array element, d is the transmitting array element spacing, K a is the Doppler modulation frequency, K r The frequency is modulated in the distance direction.

10. A SAR deception jamming device based on range-azimuth two-dimensional modulation, characterized in that: The SAR deception jamming device based on range-azimuth two-dimensional modulation comprises: A first determination module is used to determine the SAR signal intercepted by the jammer according to the SAR transmission signal and the instantaneous slant range from the jammer to the SAR; A second determination module is used to determine an interference signal according to an instantaneous slant range difference between the jammer and the target, a range offset in the range direction, a range offset in the azimuth direction, and a SAR signal intercepted by the jammer, wherein the interference signal includes an active cancellation signal and a range-azimuth two-dimensional modulation phase; A carrier frequency removal processing module is used to perform carrier frequency removal processing on the echo signal received by the SAR to obtain the echo signal after the carrier frequency is removed, and the echo signal received by the SAR is the sum of the interference signal and the target echo signal; The imaging processing module is used to perform imaging processing on the echo signal after the carrier frequency is removed by using a range Doppler algorithm to obtain an echo signal after imaging processing, and the echo signal after imaging processing is used to indicate the generation of multiple false targets.

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