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

Abstract

The application provides a SAR deception jamming method and device based on range-azimuth two-dimensional modulation, and relates to the technical field of radar signal processing. The method comprises the following steps: determining a SAR signal intercepted by a jammer according to a transmission signal of the SAR and an instantaneous slant range from the jammer to the SAR; determining a jamming signal according to a difference between instantaneous slant ranges between the jammer and a target, a distance offset in the range direction, a distance offset in the azimuth direction, and the SAR signal intercepted by the jammer, wherein the jamming signal comprises an active cancellation signal and a range-azimuth two-dimensional modulation phase; performing de-carrier frequency processing on a received echo signal of the SAR to obtain a de-carrier frequency echo signal, wherein the received echo signal of the SAR is a sum of the jamming signal and a target echo signal; and performing imaging processing on the de-carrier frequency echo signal by using a range-Doppler algorithm to obtain an imaging-processed echo signal, so that a diversified jamming effect can be achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of radar signal processing, and particularly relates to a SAR deception jamming method and device based on range-azimuth two-dimensional modulation. BACKGROUND

[0002] Due to the advantages of all-weather and all-day operation and strong information acquisition capability, synthetic aperture radar (SAR) has extremely important application value in the fields of earth observation and reconnaissance surveillance. In order to protect the target from illegal detection and reconnaissance, implementing effective deception jamming on the SAR reconnaissance system has always been a research hotspot in the field of electronic countermeasures. The deception jamming technology radiates electromagnetic waves similar to target echoes to generate false targets in the imaging results, affect the identification of real targets by the SAR reconnaissance system, and weaken the information acquisition capability thereof.

[0003] At present, a spaceborne SAR scattering wave deception jamming method based on a frequency diversity array is adopted, a small frequency increment and an additional distance dimension degree of freedom are introduced into the carrier frequency of adjacent array elements, multiple false targets in the distance dimension are generated, and the positions of the multiple false targets are determined by the frequency offset. However, in the method, the real target is not hidden, and the SAR signal intercepted is only interfered with by the frequency diversity array in the distance dimension, the interference effect is relatively single, and the false target is easily identified by the SAR. SUMMARY

[0004] The purpose of the embodiments of the present application is to provide a SAR deception jamming method and device based on range-azimuth two-dimensional modulation, and solve the problem that the interference effect is relatively single and the false target is easily identified by the SAR.

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

[0006] The first aspect of the present application 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 comprises the following steps.

[0007] Determining the SAR signal intercepted by the jammer according to the transmission signal of the SAR and the instantaneous slant range from the jammer to the SAR;

[0008] Determining the interference signal 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, the interference signal comprising an active cancellation signal and a range-azimuth two-dimensional modulation phase;

[0009] Performing de-carrier frequency processing on the echo signal received by the SAR to obtain the echo signal after de-carrier frequency processing, the echo signal received by the SAR being the sum of the interference signal and the target echo signal;

[0010] The echo signal after the de-chirp processing is processed by using a range-doppler algorithm to obtain an echo signal after imaging processing, and the echo signal after imaging processing is used to generate a plurality of false targets.

[0011] The second aspect of the present application provides a SAR deception jamming device based on range-azimuth two-dimensional modulation, which comprises:

[0012] The first determination module is configured to determine the SAR signal intercepted by the jammer according to the transmission signal of the SAR and the instantaneous slant range from the jammer to the SAR.

[0013] The second determination module is configured to determine the jamming signal according to the instantaneous slant range difference between the jammer and the target, the range distance offset, the azimuth distance offset, and the SAR signal, wherein the jamming signal comprises an active cancellation signal and a range-azimuth two-dimensional modulation phase.

[0014] The de-chirp processing module is configured to perform de-chirp processing on the echo signal received by the SAR to obtain an echo signal after de-chirp processing, wherein the echo signal received by the SAR is the sum of the jamming signal and the target echo signal.

[0015] The imaging processing module is configured to process the echo signal after de-chirp processing by using a range-doppler algorithm to obtain an echo signal after imaging processing, and the echo signal after imaging processing is used to generate a plurality of 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 application determine the SAR signal intercepted by the jammer according to the transmission signal of the SAR and the instantaneous slant range from the jammer to the SAR, determine the jamming signal according to the instantaneous slant range difference between the jammer and the target, the range distance offset, the azimuth distance offset, and the SAR signal intercepted by the jammer, wherein the jamming signal comprises an active cancellation signal and a range-azimuth two-dimensional modulation phase, perform de-chirp processing on the echo signal received by the SAR to obtain an echo signal after de-chirp processing, wherein the echo signal received by the SAR is the sum of the jamming signal and the target echo signal, and process the echo signal after de-chirp processing by using a range-doppler algorithm to obtain an echo signal after imaging processing, wherein the echo signal after imaging processing is used to indicate the generation of a plurality of false targets. In this way, the range-azimuth two-dimensional modulation phase is introduced, so that the echo signal after imaging processing obtained finally is used to generate a plurality of false targets in the range dimension and the azimuth dimension, the positions of the plurality of false targets can be flexibly changed and accurately controlled, and diversified jamming effects can be achieved. In addition, the echo signal received by the SAR is the sum of the jamming signal and the target echo signal, the active cancellation of the target echo signal can be realized, the real target can be hidden on the SAR image, and it is difficult for the SAR reconnaissance system to identify the real target from the plurality of false targets. Attached Figure Description

[0017] The above and other objects, features, and advantages of exemplary embodiments of the present invention will become readily apparent upon reading the following detailed description with reference to the accompanying drawings. In the drawings, several embodiments of the invention are illustrated by way of example and not limitation, with the same or corresponding reference numerals denoteing the same or corresponding parts, wherein:

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

[0019] Figure 2 A flowchart illustrating a SAR deception jamming method based on range-azimuth two-dimensional modulation is shown.

[0020] Figure 3 A schematic diagram of the target imaging results is shown.

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

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

[0023] Figure 6 A schematic diagram of a SAR deception jamming device based on range-azimuth two-dimensional modulation is shown. Detailed Implementation

[0024] Exemplary embodiments of the invention will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the invention are shown in the drawings, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the invention and to fully convey the scope of the invention to those skilled in the art.

[0025] It should be noted that, unless otherwise stated, the technical or scientific terms used in this invention should have the ordinary meaning as understood by one of ordinary skill in the art.

[0026] The methods described in the embodiments of the present invention will be explained in detail below.

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

[0028] Figure 2 The flow chart of the SAR deception jamming method based on range and azimuth two-dimensional modulation in the embodiment of the application is schematically shown, referring to Figure 2 The method can include:

[0029] S201, according to the transmitting signal of the SAR and the instantaneous slant range of the jammer to the SAR, the SAR signal intercepted by the jammer is determined.

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

[0031] According to the instantaneous slant range of the jammer to the SAR and the instantaneous slant range of the target to the SAR, the instantaneous slant range difference between the jammer and the target is determined.

[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] Wherein, ΔR(t a ) is the instantaneous slant range difference between the jammer and the target, R J (t a ) is the instantaneous slant range of the jammer to the SAR, Rp(ta) is the instantaneous slant range of the target to the SAR, t a is the slow time.

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

[0036] The reconnaissance receiver receives the transmission signals s(t r ,t a ) of the SARs in different slow times in turn r ,t a ) is expressed as:

[0037]

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

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

[0040]

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

[0042] S202, according to the instantaneous slant range difference between the jammer and the target, the range distance offset, the azimuth distance offset, and the SAR signal intercepted by the jammer, determine the jamming signal.

[0043] Where the jamming signal includes an active cancellation signal and a range-azimuth two-dimensional modulation phase.

[0044] Specifically, according to the instantaneous slant range difference between the jammer and the target, the range distance offset, the azimuth distance offset, and the SAR signal intercepted by the jammer, determine the jamming signal, including:

[0045] Step A1: 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.

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

[0047]

[0048] wherein 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 is the 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 is the range rate.

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

[0050] Step A2: constructing 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] wherein Sc(tr,ta) is the active cancellation signal, J1(tr,ta) is the delayed SAR signal, t r is the fast time, and t a is the slow time.

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

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

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

[0057]

[0058] wherein b m(t r ,t a ) is the range-doppler two-dimensional modulation phase of the mth transmit element, K r is the range frequency modulation, γ x,m is the range distance bias of the mth transmit element, c is the light speed, t r is the fast time, R J (t a ) is the instantaneous slant range 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 frequency modulation, γ y,m is the azimuth distance bias of the mth transmit element, V is the flight speed of the SAR, t a is the slow time.

[0059] The range-doppler two-dimensional modulation phase of the mth transmit element is a phase containing the range distance bias and the azimuth distance bias.

[0060] Step A4: determining the jamming signal according to the delayed SAR signal, the active cancellation signal and the range-doppler two-dimensional modulation phase of the mth transmit element.

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

[0062]

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

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

[0065] determining the target echo signal according to the instantaneous slant range R p (t a ) of the target to the SAR.

[0066]

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

[0068] S203. performing de-carrier frequency processing on the echo signal received by the SAR to obtain a de-carrier frequency processed echo signal.

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

[0070] In order to obtain the baseband signal, the de-carrier frequency processing needs to be performed on the echo signal received by the SAR to obtain a de-carrier frequency processed echo signal y J (t r ,t a ), and the expression of the de-carrier frequency processed echo signal y J (t r ,t a ) is:

[0071]

[0072] wherein 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 element, M is the number of transmitting elements, t r is the fast time, ta is the slow time, T p is the pulse width in range direction, T a is the synthetic aperture time, f0 is the carrier frequency, c is the speed of light, K r is the frequency modulation in range direction, γ x,m is the range distance bias of the mth transmitting element, γ y,m is the range distance bias of the mth transmitting element, K a is the Doppler frequency modulation, V is the flight speed of the SAR, R m (t a ) is the equivalent instantaneous slant range of 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 range of 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 of the mth transmitting element to the SAR.

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

[0074] Wherein, the echo signal after imaging processing is used to indicate that a plurality of false targets are generated.

[0075] Specifically, using a range Doppler algorithm, the echo signal after the carrier frequency is removed is processed to obtain an echo signal after imaging processing, including:

[0076] Step B1: using Fourier transform, the echo signal after the carrier frequency is removed is transformed into a range frequency domain to obtain a range frequency domain echo signal.

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

[0078]

[0079] Wherein, y J (tr,ta) is the echo signal after the carrier frequency is removed, f r is the range frequency, t r is the fast time, m is the mth transmitting element, M is the number of transmitting elements, K r is the frequency modulation in range direction, γ x,m is the range distance bias of the mth transmitting element, γy,m is the azimuth distance offset of the mth transmit 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 of the false target to the SAR, K a is the Doppler frequency rate, V is the flight speed of the SAR, B r is the range bandwidth, B r = K r T p , T p is the range pulse width.

[0080] Step B2: determining the frequency domain range compressed echo signal according to the range frequency domain echo signal and the range matched filtering reference function.

[0081] Specifically, the range matched filtering reference function H r (f r ) = exp(jπf r 2 K r ) is constructed, the range frequency domain echo signal is multiplied by the range matched filtering reference function, and a frequency domain range compressed echo signal y J,rc (f r , t a ) is obtained. An expression of the frequency domain range compressed echo signal y J,rc (f r , t a ) is as follows:

[0082]

[0083] Wherein, m is the mth transmit element, M is the number of transmit elements, f r is the range frequency, K r is the range frequency rate, c is the speed of light, γ x,m is the range distance offset of the mth transmit element, γ y,m is the azimuth distance offset of the mth transmit 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 of the false target to the SAR, K a is the Doppler frequency rate, V is the flight speed of the SAR.

[0084] Step B3: performing inverse Fourier transform on the frequency domain range compressed echo signal to obtain a time domain range compressed echo signal.

[0085] An expression of the time domain range compressed echo signal y J,rc (t r , t a ) is as follows:

[0086]

[0087] Among them, y J rc(fr,ta) is the frequency-domain distance-compressed echo signal, f r For distance frequency, t r To save time, B r For range bandwidth, Br = KrTp, where 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, and γ is the range bandwidth. x,m γ is the range offset of the m-th transmitting element. y,m T is the azimuth range offset of the m-th transmitting element. a Where f is the synthesis aperture time, f0 is the carrier frequency, and K is the number of atoms in the array. r For the range-directed modulation frequency, K a V is the Doppler frequency modulation, and V is the SAR's flight speed.

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

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

[0090]

[0091] Among them, y J rc(tr,ta) is the echo signal after time-domain distance compression, f a For azimuth frequency, B r For the range bandwidth, B r =K r T p T p R is the distance-oriented pulse width. m (t a ) represents the equivalent instantaneous slant range from the false target to the SAR, c is the speed of light, and γ is the slant range. x,m γ is the range offset of the m-th transmitting element. y,m x is the azimuth range offset of the m-th transmitting element. p V represents the target's azimuth, V represents the SAR's flight speed, and T represents the target's position. a The synthesis aperture time is given by f0, and the carrier frequency is given by R. P0 Let d be the shortest slant range from the target to the SAR, θ be the element spacing, and K be the target's viewing angle. a To tune the 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 then perform an inverse azimuth Fourier transform on the multiplied echo signal to obtain the image-processed echo signal.

[0093] Specifically, construct the azimuth-direction matched filter reference function. and distance 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 distance migration correction phase function H rcmc (f r The two signals are multiplied, and the resulting echo signals are then subjected to an inverse Fourier transform in the azimuth direction to obtain the processed echo signal. The expression for the processed echo signal is as follows:

[0094]

[0095] Among them, y J,rcmc (t r ,t a ) represents the echo signal after imaging processing, y J,rc (t r ,f a H represents the azimuth frequency domain echo signal. a (f a H is the azimuth matched filter reference function. rcmc (f r ) represents the range migration correction phase function, t r To save time, f a f is the azimuth frequency. r For distance frequency, B r =K r T p B r For the range bandwidth, B a R is the Doppler bandwidth. P0 Let γ be the shortest slant range from the target to the SAR, c be the speed of light, and γ be the slant range. x,m For the range offset of the m-th transmitting element, t a For slow time, x p γ represents the target's location. y,m Let V be the azimuth range offset of the m-th transmitting element, V be the SAR flight velocity, f0 be the carrier frequency, m be the m-th transmitting element, d be the spacing between transmitting elements, and K be the distance between transmitting elements. a For Doppler frequency modulation, K r This is the range-directed frequency modulation.

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

[0097] The system parameters of the simulation are as follows: the SAR platform flight height is 10 km, the speed is 250 m / s, the working 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 schematic diagram is schematically shown, the horizontal coordinate is the range, and the vertical coordinate is the azimuth, and the target is located at the scene center position. 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, wherein, [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 range distance offset of the mth transmitting array element, wherein, m = 1, 2, …, M, m is the mth 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 coordinate is the range, and the vertical coordinate is the azimuth, [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, and the number of false targets is related to the number of array elements, and the distance bias γ x,m and the azimuth distance bias γ y,m determine the distance position and azimuth position of each false target in the SAR image.

[0099] Based on the above Figure 1 It can be seen that, according to the SAR transmitting signal and the instantaneous slant range of the jammer to the SAR, the SAR signal intercepted by the jammer is determined; according to the instantaneous slant range difference between the jammer and the target, the distance bias in the range direction, the distance bias in the azimuth direction, and the SAR signal intercepted by the jammer, the jamming signal is determined, the jamming signal includes an active cancellation signal and a range-azimuth two-dimensional modulation phase; the echo signal received by the SAR is subjected to de-carrier frequency processing to obtain a de-carrier frequency echo signal; the de-carrier frequency echo signal is subjected to imaging processing using a range-doppler algorithm 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 introduction of the range-azimuth two-dimensional modulation makes the finally obtained imaging-processed echo signal used to generate multiple false targets in the range dimension and the azimuth dimension, so that the positions of the multiple false targets can be flexibly changed and accurately controlled to achieve diversified jamming effects; in addition, the echo signal received by the SAR is the sum of the jamming signal and the target echo signal, so that the active cancellation of the target echo signal can be realized, the real target can be hidden on the SAR image, and it is difficult for the SAR reconnaissance system to identify the real target from the 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, the embodiment of the present application also provides a SAR deception jamming device based on range-azimuth two-dimensional modulation. Figure 6 The structural diagram of the device in the embodiment of the present application is shown in Figure 6 The device can include:

[0101] The first determination module 601 is configured to determine the SAR signal intercepted by the jammer according to the SAR transmitting signal and the instantaneous slant range of the jammer to the SAR;

[0102] The second determining module 602 is configured to determine the jamming signal according to the instantaneous slant range difference between the jammer and the target, the distance bias in the range direction, the distance bias in the azimuth direction and the SAR signal intercepted by the jammer, the jamming signal including an active cancellation signal and a range-azimuth two-dimensional modulation phase.

[0103] The off-carrier frequency processing module 603 is configured to perform off-carrier frequency processing on the echo signal received by the SAR to obtain an off-carrier frequency echo signal, the echo signal received by the SAR being a sum of the jamming signal and a target echo signal.

[0104] The imaging processing module 604 is configured to perform imaging processing on the off-carrier frequency echo signal by using a range-Doppler algorithm to obtain an imaging-processed echo signal, the imaging-processed echo signal being used to generate a plurality of false targets.

[0105] The apparatus further includes a third determining module configured to, before determining the SAR signal intercepted by the jammer according to the transmission signal of the SAR and the instantaneous slant range of the jammer to the SAR, determine the instantaneous slant range difference between the jammer and the target according to the instantaneous slant range of the jammer to the SAR and the instantaneous slant range of the target to the SAR.

[0106] The second determining module 602 is specifically configured to perform delay processing on the SAR signal intercepted by the jammer according to the instantaneous slant range difference between the jammer and the target to obtain a delayed SAR signal, construct an active cancellation signal according to the delayed SAR signal, construct a range-azimuth two-dimensional modulation phase of the mth transmission element according to the distance bias in the range direction and the distance bias in the azimuth direction, and determine the jamming signal according to the delayed SAR signal, the active cancellation signal and the range-azimuth two-dimensional modulation phase of the mth transmission element.

[0107] The second determining module 602 is specifically configured to perform delay processing on the SAR signal intercepted by the jammer according to the instantaneous slant range difference between the jammer and the target to obtain a delayed SAR signal, construct an active cancellation signal according to the delayed SAR signal, construct a range-azimuth two-dimensional modulation phase of the mth transmission element according to the distance bias in the range direction and the distance bias in the azimuth direction, and determine the jamming signal according to the delayed SAR signal, the active cancellation signal and the range-azimuth two-dimensional modulation phase of the mth transmission element.

[0108]

[0109] wherein J1(tr, ta) is the delayed SAR signal, Jr(tr, ta) is the SAR signal, t r is a fast time, t a is a slow time, δ is an 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 of the jammer to the SAR, T a is a synthetic aperture time, f0 is a carrier frequency, and K r is a range direction frequency modulation.

[0110] The second determining module 602 is specifically configured to perform delay processing on the SAR signal intercepted by the jammer according to the instantaneous slant range difference between the jammer and the target to obtain a delayed SAR signal, construct an active cancellation signal according to the delayed SAR signal, construct a range-azimuth two-dimensional modulation phase of the mth transmission element according to the distance bias in the range direction and the distance bias in the azimuth direction, and determine the jamming signal according to the delayed SAR signal, the active cancellation signal and the range-azimuth two-dimensional modulation phase of the mth transmission element.

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

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

[0113] The second determination module 602, the expression of the range-doppler two-dimensional modulation phase of the transmitting array element is:

[0114]

[0115] wherein b m (t r ,t a ) is the range-doppler two-dimensional modulation phase of the mth transmitting array element, K r is the range frequency modulation, γ x,m is the range distance offset of the mth transmitting array element, c is the light speed, t r is the fast time, R J (t a ) is the instantaneous slant range 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 frequency modulation, γ y,m is the azimuth distance offset of the mth transmitting array element, V is the flight speed of the SAR, t a is the slow time.

[0116] The second determination module 602, the expression of the jamming signal is:

[0117]

[0118] wherein J2(tr,ta) is the jamming signal, J1(tr,ta) is the delayed SAR signal, t r is the fast time, t a is the slow time, b m (t r ,t a ) is the range-doppler 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 range from the jammer to the SAR, ΔR(ta ) is the instantaneous slant range difference between the jammer and the target, c is the light speed, f0 is the carrier frequency, T p is the pulse width in the range direction, T a is the synthetic aperture time, K r is the frequency modulation rate in the range direction, γ x,m is the range distance offset of the mth transmitting array element, γ y,m is the range distance offset of the mth transmitting array element, K a is the Doppler frequency modulation rate, and V is the flight speed of the SAR.

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

[0120] The imaging processing module 604, and an expression of the imaging processed echo signal is:

[0121]

[0122] Wherein, y J,rcmc (t r ,t a ) is the imaging processed echo signal, y J,rc (t r ,f a ) is the azimuth frequency domain echo signal, H a (f a ) is the azimuth direction matched filter reference function, H rcmc (f r ) is the range migration correction phase function, t r is the fast time, f a is the azimuth frequency, f r is the range frequency, B r = K r T p , B r is the range direction bandwidth, B a is the Doppler bandwidth, R P0 is the shortest slant range of the target to the SAR, c is the light speed, γ x,m is the range distance offset of the mth transmitting array element, t aslow time, x p target azimuth position, γ y,m azimuth distance offset of the mth transmit element, V is the flight speed of the SAR, f0 is the carrier frequency, m is the mth transmit element, d is the transmit element spacing, K a Doppler frequency modulation, K r range frequency modulation.

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

[0124] The above is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto, any person skilled in the art can easily think of changes or replacements within the technical scope disclosed by the present application, which should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to 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 the range-azimuth two-dimensional modulation comprises the following steps: determining the SAR signal intercepted by the jammer according to the transmission signal of the SAR and the instantaneous slant range from the jammer to the SAR; determining the jamming signal according to the instantaneous slant range difference between the jammer and the target, the range distance offset, the azimuth distance offset and the SAR signal intercepted by the jammer, wherein the jamming signal comprises an active cancellation signal and a range-azimuth two-dimensional modulation phase; performing de-carrier processing on the echo signal received by the SAR to obtain a de-carrier echo signal, wherein the echo signal received by the SAR is the sum of the jamming signal and the target echo signal; performing imaging processing on the de-carrier echo signal by using a range-Doppler algorithm to obtain an imaging-processed echo signal, wherein the imaging-processed echo signal is used to indicate a plurality of false targets; before determining the SAR signal intercepted by the jammer according to the transmission signal of the SAR and the instantaneous slant range from the jammer to the SAR, the method further comprises the following steps: determining 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; the step of determining the jamming signal according to the instantaneous slant range difference between the jammer and the target, the range distance offset, the azimuth distance offset and the SAR signal intercepted by the jammer comprises the following steps: delaying the SAR signal intercepted by the jammer according to the instantaneous slant range difference between the jammer and the target to obtain a delayed SAR signal; constructing the active cancellation signal according to the delayed SAR signal; According to the distance-to-distance bias and the azimuth-to-distance bias, a distance-azimuth two-dimensional modulation phase of the first transmitting element is constructed. ​ According to the time-delayed SAR signal, the active cancellation signal and the range-doppler two-dimensional modulation phase of the first transmitting element, the interference signal is determined. ​ 2. The method of claim 1, wherein the method is characterized by, an expression of the delayed SAR signal is as follows: ； wherein, is the delayed SAR signal, is the SAR signal intercepted by the jammer, is fast time, is slow time, is an impulse function, is the instantaneous slant range difference between the jammer and the target, is the speed of light, is the instantaneous slant range of the jammer to the SAR, is the synthetic aperture time, is the carrier frequency, is the range chirp rate, is the range pulse width.

3. The method of claim 2, wherein the method is characterized by, an expression of the active cancellation signal is as follows: ； wherein, is the active cancellation signal, is the delayed SAR signal, is the fast time, is the slow time.

4. The method of claim 1, wherein the method is characterized by, The first The expression of the distance and azimuth two-dimensional modulation phase of the first transmitting element is: ； wherein, is the distance direction modulation phase of the jthtransmit element, is the distance direction modulation phase of the jthtransmit element, is the distance direction frequency, is the distance direction distance offset of the jthtransmit element, is the distance direction distance offset of the jthtransmit element, is the speed of light, is the fast time, is the instantaneous slant range of the jammer to the SAR, is the instantaneous slant range difference between the jammer and the target, is the Doppler frequency, is the azimuth direction distance offset of the jthtransmit element, is the azimuth direction distance offset of the jthtransmit element, is the flight speed of the SAR, is the slow time.

5. The method of claim 1, wherein the method is characterized by, an expression of the jamming signal is as follows: ； wherein, is the jammer, is the delayed SAR signal, is fast time, is slow time, is the distance- azimuth two-dimensional modulation phase of the th transmit element, is the active cancellation signal, is the number of transmit elements, is the instantaneous slant range of the jammer to the SAR, is the instantaneous slant range difference between the jammer and the target, is the speed of light, is the carrier frequency, is the range-azimuth pulse width, is the synthetic aperture time, is the range-azimuth frequency modulation rate, is the range-azimuth range offset of the th transmit element, is the azimuth-azimuth range offset of the th transmit element, is the Doppler frequency modulation rate, is the flight speed of the SAR.

6. The method of claim 1, wherein the method is characterized by, the step of performing imaging processing on the de-carrier echo signal by using a range-Doppler algorithm to obtain an imaging-processed echo signal comprises the following steps: transforming the de-carrier echo signal into a range frequency domain by using a Fourier transform to obtain a range frequency domain echo signal; determining a frequency domain range compressed echo signal according to the range frequency domain echo signal and a range matching filter reference function; performing inverse Fourier transform on the frequency domain range compressed echo signal to obtain a time domain range compressed echo signal; performing azimuth Fourier transform on the time domain range compressed echo signal to obtain an azimuth frequency domain echo signal; multiplying the azimuth frequency domain echo signal, an azimuth matching filter reference function and a range migration correction phase function, and performing azimuth inverse Fourier transform on the multiplied echo signal to obtain the imaging-processed echo signal.

7. The method of claim 6, wherein the method is characterized by, an expression of the imaging-processed echo signal is as follows: ； wherein, is the imaging processed echo signal, is the azimuth frequency domain echo signal, is the azimuth matched filter reference function, is the range migration correction phase function, is fast time, is azimuth frequency, is range frequency, , is range bandwidth, is Doppler bandwidth, is the shortest slant range of the target to the SAR, is the speed of light, is the range distance offset of the th transmit array element, is slow time, is the azimuth position of the target, is the azimuth distance offset of the th transmit array element, is the flight speed of the SAR, is the carrier frequency, is the th transmit array element, is the transmit array element spacing, is the Doppler frequency modulation, is the range frequency modulation, is the range pulse width, is the target aspect angle.

8. A SAR deception jamming device based on range-azimuth two-dimensional modulation, characterized in that, The SAR deception jamming device based on the range-azimuth two-dimensional modulation comprises the following steps: a first determining module is configured to determine the SAR signal intercepted by the jammer according to the transmission signal of the SAR and the instantaneous slant range from the jammer to the SAR; The second determining module is configured to determine an interference signal according to the instantaneous slant range difference between the jammer and the target, the distance offset, the azimuth offset, and the SAR signal intercepted by the jammer, wherein the interference signal comprises an active cancellation signal and a two-dimensional modulation phase in the range-azimuth direction. The dechirp processing module is configured to perform dechirp processing on the echo signal received by the SAR to obtain a dechirped echo signal, wherein the echo signal received by the SAR is a sum of the interference signal and a target echo signal. The imaging processing module is configured to perform imaging processing on the dechirped echo signal by using a range-Doppler algorithm to obtain an imaging-processed echo signal, wherein the imaging-processed echo signal is used to indicate a plurality of false targets. The device further comprises a third determining module configured 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 transmission signal of the SAR and the instantaneous slant range from the jammer to the SAR. The second determining module is specifically configured to perform delay processing on the SAR signal intercepted by the jammer according to an instantaneous slant range difference between the jammer and the target, to obtain a delayed SAR signal; construct the active cancellation signal according to the delayed SAR signal; construct a range-bearings two-dimensional modulation phase of a first transmitting element according to the range direction distance bias and the bearing direction distance bias; and determine the jamming signal according to the delayed SAR signal, the active cancellation signal and the range-bearings two-dimensional modulation phase of the first transmitting element. The second determining module is specifically configured to perform delay processing on the SAR signal intercepted by the jammer according to an instantaneous slant range difference between the jammer and the target, to obtain a delayed SAR signal; construct the active cancellation signal according to the delayed SAR signal; construct a range-bearings two-dimensional modulation phase of a first transmitting element according to the range direction distance bias and the bearing direction distance bias; and determine the jamming signal according to the delayed SAR signal, the active cancellation signal and the range-bearings two-dimensional modulation phase of the first transmitting element.​

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