A multi-mode SAR jamming method and device

Abstract

The present invention discloses a multi-mode SAR jamming method and device, belonging to the field of radar electronic countermeasures. The method comprises: in the jamming preparation phase, calculating the product matrix of each jamming mode; after entering the reconnaissance phase, intercepting the first segment of the received signal and determining whether it is a SAR signal, estimating the parameters of the SAR signal, and extracting a complete SAR pulse signal frame as a reference signal; intercepting the second segment of the received signal and determining whether to enter the jamming phase based on the PRF; after entering the jamming phase, receiving a portion of the SAR pulse signal and restoring it to a complete SAR pulse signal; multiplying the complete SAR pulse signal by the product matrix to obtain a baseband jamming signal; modulating the baseband jamming signal into a radio frequency jamming signal and transmitting the signal. The present invention can implement multiple jamming modes such as false target implantation, pseudo radio frequency jamming, and scattered wave jamming, and the jamming signal modulation complexity is low, and the jamming device has low isolation requirements for the transmitting and receiving antennas.

Description

Technical Field

[0001] The present invention relates to the field of radar electronic countermeasures, and in particular to a multi-mode SAR jamming method and device. Background Art

[0002] Synthetic aperture radar (SAR) is an imaging radar technology that can acquire high-resolution ground images under various lighting and weather conditions. It is widely used in fields such as environmental monitoring. However, electronic jamming of SAR is necessary to protect sensitive targets.

[0003] Among various jamming methods, forwarding jamming maintains coherence between the jamming signal and the SAR signal to improve the matched filter gain. Forwarding jamming requires a jammer (also known as a jammer) to first receive the SAR pulse signal, modulate it into a jamming signal, and then transmit it. Since SAR pulses are typically very long (the pulse duration of spaceborne SAR can reach tens of microseconds), the jammer may need to receive and transmit signals simultaneously. To prevent the transmitted signal from affecting the received signal, the receiving and transmitting antennas must achieve high isolation. However, the need for high isolation between the receiving and transmitting antennas hinders the development of low-cost and miniaturized jammers. Although existing jamming methods use intermittent sampling and forwarding jamming, which can time-share signal reception and transmission and eliminate the need for high isolation between the receiving and transmitting antennas, the resulting jamming patterns are highly regular and easily detected by radar detectors.

[0004] On the other hand, achieving precise deceptive jamming typically requires computationally complex frequency-domain modulation, requiring enormous amounts of computing power, which hinders the development of low-cost jammers. While time-domain modulation of jamming signals is possible, such methods can cause significant distortion at the edges of the jamming pattern, leading to false targets. Furthermore, there is currently a lack of jamming methods that utilize product modulation to achieve multiple jamming patterns. Summary of the Invention

[0005] To address the high isolation requirements for transceiver antennas and the massive computing resources required for precise deceptive interference, which makes it difficult to achieve low-cost and miniaturized jammers, the present invention provides a multi-mode SAR jamming method and device. This method reduces the high isolation requirements for transceiver antennas by first receiving partial SAR pulses and then restoring them to complete SAR pulses. An optimized product modulation method is used to achieve precise and computationally low-complexity deceptive interference (false target implantation mode). Other jamming modes (i.e., pseudo-RF interference mode and scattered wave interference mode) can also be achieved through the product modulation method. Pseudo-RF interference refers to an interference pattern in which the interference signal in the time, frequency, and image domains is similar to the characteristics of unintentional RF interference in reality. This type of interference is less likely to be identified as intentional interference, thereby reducing the probability of the jammer and the shielded target being discovered.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A multi-mode SAR jamming method, comprising:

[0008] In the jamming preparation phase, the product matrices of the false target implantation pattern, the pseudo radio frequency jamming pattern and the scattered wave jamming pattern are calculated respectively;

[0009] After entering the reconnaissance phase, intercept the first segment of the received signal;

[0010] Determine whether the first segment of the received signal is a SAR signal, estimate the parameters of the SAR signal, and extract a complete frame of the SAR pulse signal as a reference signal;

[0011] Intercept the second segment of the received signal and determine whether it has entered the interference phase based on the PRF; PRF stands for pulse repetition frequency;

[0012] After entering the jamming phase, some SAR pulse signals are received according to the timing control;

[0013] Restoring a partial SAR pulse signal to a complete SAR pulse signal;

[0014] Multiplying the complete SAR pulse signal with the product matrix of the selected false target implantation pattern, pseudo radio frequency interference pattern or scattered wave interference pattern to obtain a preliminary modulated interference signal;

[0015] Performing Doppler phase modulation and time delay modulation on the initially modulated interference signal to obtain a baseband interference signal;

[0016] The baseband interference signal is modulated into a radio frequency interference signal, and the radio frequency interference signal is transmitted to the SAR or a designated ground area within a corresponding time period.

[0017] Furthermore, in the interference preparation stage, the product matrices of the false target implantation pattern, the pseudo radio frequency interference pattern, and the scattered wave interference pattern are calculated respectively, including:

[0018] Calculate the product matrix of the false target implantation pattern ;

[0019] Calculate the product matrix of the pseudo RFI pattern ;

[0020] Calculate the product matrix of the scattered wave interference pattern ;

[0021] The jammer loads the corresponding product matrix according to the jamming mode selected by the user.

[0022] Furthermore, the product matrix of the false target implantation pattern is calculated include:

[0023] Perform azimuth interpolation and zero padding on each column vector of the false target pattern matrix, and then concatenate the zero-padded column vectors to obtain the matrix ;

[0024] Pair Matrix Divide the blocks into azimuths and calculate the corresponding product matrices ,in is the serial number of the block matrix;

[0025] Accumulate the product matrices corresponding to all blocks , get the product matrix of the false target implantation pattern .

[0026] Furthermore, for the matrix Divide the blocks into azimuths and calculate the corresponding product matrices include:

[0027] Pair Matrix Perform azimuth block division to obtain the block matrix ;

[0028] The block matrix is interpolated and filled with zeros Mapped to the two-dimensional time domain, we get the matrix ;

[0029] Pair Matrix Perform inverse fast Fourier transform on each column of ;

[0030] Pair Matrix Each column of compensates the Doppler modulation frequency relative to the center of the interference pattern, and the matrix ;

[0031] Pair Matrix Perform inverse fast Fourier transform on each row of ;

[0032] Pair Matrix Compensate for the distance migration relative to the center of the interference pattern and calculate the product matrix .

[0033] Furthermore, the product matrix of the pseudo-RFI pattern is calculated include:

[0034] Calculate the time mask matrix of pseudo-RF interference ;

[0035] The time mask matrix of pseudo-RF interference Multiply the distance frequency signal and the linear frequency modulation signal to get the matrix :

[0036] ;

[0037] Among them, exp is the exponential function, j represents the imaginary unit, represents pi, is the frequency shift column vector, represents the distance-to-time row vector, is the column vector of range frequency modulation compensation, represents the Hadamard product of matrices;

[0038] The matrix Multiply the low-frequency noise in the distance direction to get the matrix :

[0039] ;

[0040] in, Indicates 1 line A matrix with all 1s in its columns, is the number of rows of the preset product matrix, is the noise row vector;

[0041] The matrix Multiplied by the azimuth low-frequency noise and linear frequency modulation signal, the product matrix is the RF interference pattern :

[0042] ;

[0043] in, is the noise column vector, which has been low-pass filtered in azimuth. Indicates 1 line A matrix with all 1s in its columns, is the number of columns of the preset product matrix, and the superscript T represents the transpose of the matrix. is the Doppler modulation frequency of the azimuth linear frequency modulation signal, is the azimuthal time column vector.

[0044] Furthermore, the time mask matrix of pseudo-RF interference is calculated include:

[0045] Generate a two-dimensional time matrix according to the following formula :

[0046] ;

[0047] The time mask matrix of pseudo-RF interference is calculated as follows The value of each element of :

[0048] ;

[0049] in, is a matrix The cth row and dth column element, mod represents the remainder function, is a matrix The element in row c and column d of is the pulse repetition period of the pseudo-RF interference, is the pulse duration of the spurious RFI.

[0050] Furthermore, the product matrix of the scattered wave interference pattern is calculated include:

[0051] Set up interference areas, including a main interference area and Additional interference areas; set the range coordinates and azimuth coordinates of the center of each interference area, and calculate the real-time distance from the center of the main interference area to the SAR based on the track or orbit parameters of the SAR platform , and the real-time distance from the center of each additional interference area to the SAR , is the serial number of the additional interference area; and Both Column vector of rows, each row corresponds to an azimuth time;

[0052] According to the real-time distance from the center of the main interference area to the SAR And the real-time distance from the center of each additional interference area to the SAR , calculate the Doppler phase difference and time delay of the additional interference area relative to the main interference area, and obtain the product matrix of the scattered wave interference pattern :

[0053] ;

[0054] in, is the speed of light, is the modulation frequency of the SAR signal, is the wavelength of SAR.

[0055] Furthermore, after entering the interference phase, receiving part of the SAR pulse signal according to the timing control includes:

[0056] Calculate the following formula The start time of the receiving window of the pulse :

[0057] ;

[0058] in, is the pulse number, It is The start time of the receiving window of a pulse, is the pulse repetition frequency, The first The frequency difference of the partial SAR pulse signal relative to the reference signal;

[0059] The electromagnetic signal within the receiving frequency band is down-converted and digitally sampled to obtain a digital signal, and the The digital signal within the time period is used as a partial SAR pulse signal, where is the receive window length.

[0060] Furthermore, modulating the baseband interference signal into a radio frequency interference signal, and transmitting the radio frequency interference signal to the SAR or a designated ground area within a corresponding time period includes:

[0061] Calculate the following formula The emission window start time of each pulse and launch window time period :

[0062] ;

[0063] ;

[0064] in, is the integer sampling point partial delay to be modulated, is the emission window length, symbol It means finding the difference between two sets;

[0065] The baseband interference signal is up-converted and converted into digital-to-analog form, modulated into a radio frequency interference signal, and then transmitted to the SAR or a designated ground area within the transmission window.

[0066] The present invention also provides a multi-mode SAR jammer, comprising:

[0067] A receiving antenna is used to convert the electromagnetic waves emitted by the SAR propagating in space into electromagnetic signals on the transmission line;

[0068] The transmitting antenna is used to convert the radio frequency interference signal on the transmission line into electromagnetic waves radiated in a specified direction; when the selected interference mode is the false target implantation mode or the pseudo radio frequency interference mode, the antenna points to the SAR; when the selected interference mode is the scattered wave interference mode, the antenna points to the ground scattering area;

[0069] The timing control module is used to calculate the receiving time window of the SAR signal and the transmitting time window of the interference signal, and send control instructions to the receiving module and the transmitting module;

[0070] The receiving module is used to down-convert the electromagnetic signal within the receiving frequency band and sample it to obtain a digital signal. In the reconnaissance phase, it provides the first segment of the received signal and the second segment of the received signal to the SAR signal recognition and parameter estimation module. In the interference phase, it provides part of the SAR pulse signal to the pulse recovery module.

[0071] The SAR signal identification and parameter estimation module is used to determine whether the received signal is a SAR signal and estimate the parameters of the SAR signal. It extracts a complete frame of SAR pulse signal as a reference signal, provides the PRF estimation value of the SAR signal to the timing control module, and provides the modulation frequency estimation value and reference signal of the SAR signal to the pulse recovery module. PRF stands for pulse repetition frequency.

[0072] The pulse recovery module is used to restore the partial SAR pulse signal to a complete SAR pulse signal, provide the receiving window start correction information to the timing control module, and provide the complete SAR pulse signal to the product modulation module;

[0073] A product modulation module is used to multiply the complete SAR pulse signal with the product matrix of the selected false target implantation pattern, pseudo radio frequency interference pattern or scattered wave interference pattern to obtain a preliminary modulated interference signal, and provide the preliminary modulated interference signal to the central modulation module;

[0074] The central modulation module is used to perform Doppler phase modulation and time delay modulation on the initially modulated interference signal, change the center position of the interference pattern, obtain a baseband interference signal, and provide the baseband interference signal to the transmission module;

[0075] The transmitting module is used to up-convert the baseband interference signal and perform digital-to-analog conversion to obtain the radio frequency interference signal, and output the radio frequency interference signal to the transmitting antenna.

[0076] The present invention also provides an electronic device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of the multi-mode SAR interference method when executing the program.

[0077] The present invention also provides a non-transitory computer-readable storage medium having a computer program stored thereon. When the computer program is executed by a processor, the steps of the multi-mode SAR interference method are implemented.

[0078] Beneficial effects:

[0079] On the one hand, the present invention reduces the need for high isolation between transmit and receive antennas through partial pulse reception and complete pulse recovery. In certain modes, the transmit and receive antennas can even be combined, significantly reducing the size and cost of the jammer. On the other hand, the invention employs low-computational complexity product modulation technology to implement various modes, such as decoy implantation, pseudo-RF interference, and scattered wave interference, significantly reducing the demand for computing resources and further lowering costs. Furthermore, when calculating the product matrix of the decoy implantation pattern, image domain interpolation processing, as well as compensation processing in the range-frequency domain and azimuth-time domain, effectively reduces the deformation and edge distortion of the decoy. BRIEF DESCRIPTION OF THE DRAWINGS

[0080] Figure 1 This is a structural diagram of a multi-mode SAR jammer provided by the present invention;

[0081] Figure 2 A flow chart of a multi-mode SAR jamming method provided by the present invention;

[0082] Figure 3 A SAR image of area 1 without interference provided by an embodiment of the present invention;

[0083] Figure 4 A SAR image of area 1 that is interfered with in a false target implantation mode provided by an embodiment of the present invention;

[0084] Figure 5 A SAR image of area 1 interfered with in a pseudo radio frequency interference mode provided by an embodiment of the present invention;

[0085] Figure 6 The SAR image of area 2 without interference provided by the embodiment of the present invention;

[0086] Figure 7 This is a SAR image of region 2 that is interfered with in the scattered wave interference mode provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0087] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only intended to illustrate the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0088] The present invention calculates the product matrix of different interference patterns, intercepts the received signal during the reconnaissance phase and determines whether it is a SAR signal. It then determines whether to enter the interference phase based on the pulse repetition frequency and recovers part of the SAR pulse signal. The recovered SAR pulse signal is multiplied by the interference pattern matrix, then Doppler phase modulation and time delay modulation are performed to generate a baseband interference signal, which is then modulated into a radio frequency signal for transmission.

[0089] like Figure 1 As shown, an embodiment of the present invention provides a multi-mode SAR jamming device, which includes:

[0090] A receiving antenna is used to convert the electromagnetic waves emitted by the SAR propagating in space into electromagnetic signals on the transmission line;

[0091] The transmitting antenna is used to convert the radio frequency interference signal on the transmission line into electromagnetic waves radiated in a specified direction. When the selected interference mode is the false target implantation mode or the pseudo radio frequency interference mode, the antenna points to the SAR; when the selected interference mode is the scattered wave interference mode, the antenna points to the ground scattering area;

[0092] The timing control module is used to calculate the receiving time window of the SAR signal and the transmitting time window of the interference signal, and send control instructions to the receiving module and the transmitting module;

[0093] The receiving module is used to down-convert the electromagnetic signal within the receiving frequency band and sample it to obtain a digital signal. In the reconnaissance phase, it provides the first segment of the received signal and the second segment of the received signal to the SAR signal recognition and parameter estimation module. In the interference phase, it provides part of the SAR pulse signal to the pulse recovery module.

[0094] SAR signal identification and parameter estimation module, used to determine whether the received signal is a SAR signal, estimate the parameters of the SAR signal, extract a complete frame of SAR pulse signal as a reference signal, provide the PRF estimation value of the SAR signal to the timing control module, and provide the SAR signal frequency modulation estimation value and reference signal to the pulse recovery module;

[0095] The pulse recovery module is used to restore the partial SAR pulse signal to a complete SAR pulse signal, provide the receiving window start correction information to the timing control module, and provide the complete SAR pulse signal to the product modulation module;

[0096] The product modulation module is used to multiply the complete SAR pulse signal with the product matrix to obtain a preliminary modulated interference signal, and provide the preliminary modulated interference signal to the central modulation module;

[0097] The central modulation module is used to perform Doppler phase modulation and time delay modulation on the initially modulated interference signal, change the center position of the interference pattern, obtain a baseband interference signal, and provide the baseband interference signal to the transmission module;

[0098] The transmitting module is used to up-convert the baseband interference signal and perform digital-to-analog conversion to obtain the radio frequency interference signal, and output the radio frequency interference signal to the transmitting antenna.

[0099] In the false target implantation mode and pseudo radio frequency interference mode, the receiving antenna and the transmitting antenna can be combined into one antenna, which is connected to the receiving module and the transmitting module at the same time, and the antenna is controlled by the timing control module to complete the receiving or transmitting function.

[0100] like Figure 2 As shown, an embodiment of the present invention provides a multi-mode SAR jamming method, comprising the following steps:

[0101] Step 1: In the jamming preparation phase, the product matrices of the false target implantation mode, pseudo radio frequency jamming mode, and scattered wave jamming mode are calculated respectively. The jammer loads the corresponding product matrix according to the selected jamming mode, including:

[0102] Step 1.1. Calculate the product matrix of the false target implantation pattern.

[0103] Step 1.1.1. Perform azimuth interpolation on the false target pattern matrix to correct for interference pattern deformation caused by spatial variation of azimuth modulation frequency.

[0104] Assume that the false target pattern to be implanted by the jammer is the matrix ,matrix is a OK Matrix of columns, matrix The azimuth width of the corresponding false target is meters, and the width in the distance is The row direction (horizontal) of the matrix is the distance direction, and the column direction (vertical) is the azimuth direction.

[0105] Step 1.1.1.1, matrix Each column of is interpolated in azimuth direction, and we get Column vector of rows ,in is a matrix The column index of , Calculated by the following formula:

[0106] ;

[0107] in, is the rounding function, is the shortest distance from the jammer to the SAR.

[0108] Step 1.1.1.2: For all column vectors Fill the head and tail with zeros to get the number of rows Column vector of rows ,in .

[0109] Step 1.1.1.3. Set all column vectors Splicing in the distance direction, we get the matrix ,Right now:

[0110] ;

[0111] Step 1.1.2, matrix Divide the blocks into azimuths and calculate the corresponding product matrices respectively.

[0112] Step 1.1.2.1, matrix Perform azimuth block division to obtain the block matrix ,in is the sequence number of the block matrix, , is the number of blocks.

[0113] Block Matrix It can be obtained by the following formula:

[0114] ;

[0115] in, is a mask vector, which is a The row vector of the column, its Elements Expressed as:

[0116] ;

[0117] in, is the number of block rows.

[0118] Step 1.1.2.2, the matrix Interpolation is OK Column matrix ,in and It can be obtained by the following formula:

[0119] ;

[0120] ;

[0121] in, is the azimuth modulation frequency of the SAR signal, is the equivalent radar speed, is the speed of light, is the jammer sampling rate, is the pulse repetition frequency (PRF), is the modulation frequency of the SAR signal, is the preset number of rows of the product matrix, is the preset number of columns in the product matrix.

[0122] Step 1.1.2.3, matrix Fill the four sides of , and we get OK Column matrix .

[0123] Step 1.1.2.4, matrix Perform inverse fast Fourier transform (IFFT) on each column of .

[0124] Step 1.1.2.5: Matrix Each column of compensates the Doppler modulation frequency relative to the center of the interference pattern to solve the problem of azimuth defocusing, that is, the matrix is calculated by the following formula :

[0125] ;

[0126] ;

[0127] Among them, the symbol represents the Hadamard product of the matrix, exp represents the exponential function, j represents the imaginary unit, π represents the circumference of a circle, is the azimuthal time column vector, is the distance to position row vector, is the Doppler frequency modulation compensation row vector, is the wavelength of SAR, the superscript denotes the Hadamard power, i.e. the superscript It means to find the reciprocal of each element of the matrix.

[0128] Step 1.1.2.6, matrix Perform IFFT on each row of .

[0129] Step 1.1.2.7, matrix Compensate for the distance migration relative to the center of the interference pattern, that is, calculate the product matrix by the following formula :

[0130] ;

[0131] ;

[0132] in, It represents the frequency shift corresponding to the distance migration difference between the center of the block matrix and the center of the interference pattern, which is a column vector. represents the distance-time row vector.

[0133] Step 1.1.3: Accumulate the product matrix of all blocks , get the product matrix of the false target implantation pattern ,Right now:

[0134] ;

[0135] Step 1.2: Calculate the product matrix of the pseudo RFI pattern.

[0136] Step 1.2.1. Calculate the time mask matrix of pseudo-RF interference ,include:

[0137] Step 1.2.1.1. Generate a two-dimensional time matrix according to the following formula :

[0138] ;

[0139] in, Indicates 1 line A matrix with all 1s in its columns, Indicates 1 line A matrix with all 1s in its columns. The superscript T indicates the transpose of the matrix.

[0140] Step 1.2.1.2. Calculate the matrix according to the following formula The value of each element of :

[0141] ;

[0142] in, is a matrix The cth row and dth column element, mod represents the remainder function, is a matrix The element in row c and column d of is the pulse repetition period of the pseudo-RF interference, is the pulse duration of the spurious RFI.

[0143] Step 1.2.2, the matrix Multiply the distance frequency signal and the linear frequency modulation signal to get the matrix :

[0144] ;

[0145] in, is the frequency shift column vector, is the column vector of range frequency modulation compensation.

[0146] Step 1.2.3, matrix Multiply the low-frequency noise in the distance direction to get the matrix :

[0147] ;

[0148] in, is the noise row vector, which has been low-pass filtered in the range direction.

[0149] Step 1.2.4, the matrix Multiplied by the azimuth low-frequency noise and linear frequency modulation signal, the product matrix is the RF interference pattern :

[0150] ;

[0151] in, is the noise column vector, which has been low-pass filtered in the azimuth direction. is the Doppler modulation frequency of the azimuth linear frequency modulation signal.

[0152] Step 1.3: Calculate the product matrix of the scattered wave interference pattern.

[0153] Step 1.3.1. Set up the interference area, including a main interference area and Set the range and azimuth coordinates of the center of each interference area, and calculate the real-time distance from the center of the main interference area to the SAR based on the track or orbit parameters of the SAR platform. , and the real-time distance from the center of each additional interference area to the SAR , is the serial number of the additional interference area. and All A column vector of rows, each row corresponds to an azimuth time.

[0154] Step 1.3.2: Based on the real-time distance from the center of each interference area to the SAR, calculate the Doppler phase difference and time delay of the additional interference area relative to the main interference area, and then obtain the product matrix of the scattered wave interference pattern. , the specific calculation method is given by the following formula:

[0155] ;

[0156] Step 1.4, the jammer loads the corresponding product matrix according to the jamming mode selected by the user, with the matrix Represents the loaded product matrix, that is, if the selected interference mode is the false target implantation mode, then the loaded product matrix , and order ; If the selected interference mode is pseudo-RF interference mode, then load the product matrix , and order ; If the selected interference mode is the radio interference mode, then load the product matrix , and order .

[0157] Step 2: The jammer enters the reconnaissance phase. The receiving module down-converts the electromagnetic signal within the receiving frequency band and samples it to obtain a digital signal. The amplitude of the digital signal is used to trigger and intercept the first segment of the received signal.

[0158] Step 3: The SAR signal recognition and parameter estimation module determines whether the first segment of the received signal is a SAR signal, estimates the parameters of the SAR signal, including the modulation frequency and pulse repetition frequency (PRF), and extracts a complete frame of the SAR pulse signal as a reference signal.

[0159] Step 4: The receiving module down-converts the electromagnetic signal within the receiving frequency band and samples it to obtain a digital signal. The amplitude of the digital signal is used to trigger and intercept the second segment of the received signal. The difference between the PRF of the second segment of the received signal and the PRF of the first segment of the received signal is calculated to determine whether the interference phase has begun.

[0160] Step 5: The jammer enters the jamming phase. The receiving module receives part of the SAR pulse signal within the corresponding time period according to the instruction of the timing control module, including:

[0161] Step 5.1, the timing control module calculates the The start time of the receiving window of the pulse :

[0162] ;

[0163] in, is the pulse number, It is The start time of the receiving window of a pulse, The first The frequency difference of the partial SAR pulse signal relative to the reference signal.

[0164] Step 5.2: The receiving module down-converts and digitally samples the electromagnetic signal within the receiving frequency band to obtain a digital signal, and intercepts The digital signal within the time period is used as a partial SAR pulse signal, where: is the receive window length.

[0165] Step 6: The pulse recovery module will intercept The SAR pulse signal within the time period is restored to a complete SAR pulse signal, including:

[0166] Step 6.1, intercept The SAR pulse signal within the time period is multiplied by the conjugate of the reference signal to estimate the frequency difference and Doppler phase difference between the two.

[0167] Step 6.2, using the intercepted The estimated values of the frequency difference and Doppler phase difference between the SAR pulse signal and the reference signal within the time period are used to reconstruct a single frequency signal whose length is greater than the SAR pulse width.

[0168] Step 6.3: Multiply the single-frequency signal whose length is greater than the SAR pulse width by the reference signal to obtain the complete SAR pulse signal. , which is a Row vector of columns.

[0169] Step 7: The product modulation module converts the complete SAR pulse signal Multiplying the product matrix of the selected interference pattern to obtain the preliminary modulated interference signal, including:

[0170] Step 7.1, from the product matrix Take out the Rows get row vectors The row vector is calculated according to the following formula Time shift points :

[0171] ;

[0172] in, The first The frequency difference of the partial SAR pulse signal relative to the reference signal. Then, the row vector Time Shift sampling points, and get the row vector .

[0173] Step 7.2: Complete SAR pulse signal With row vector Multiply to get the initial modulated interference signal :

[0174] ;

[0175] Step 8: The central modulation module performs Doppler phase modulation and time delay modulation on the initially modulated interference signal to obtain a baseband interference signal, including:

[0176] Step 8.1. Set the range and azimuth coordinates of the interference pattern center and calculate the real-time distance from the interference pattern center to the SAR based on the track or orbit parameters of the SAR platform. Real-time distance from the jammer to the SAR .

[0177] Step 8.2: Preliminary modulated interference signal Perform Doppler phase modulation to obtain the row vector :

[0178] ;

[0179] Step 8.3: Calculate the partial delay of the integer sampling point to be modulated and fractional sampling point delay , and by modulating the row vector obtained in the previous step Multiply the single frequency signal to complete the partial delay modulation of the fractional sampling point to obtain the baseband interference signal :

[0180] ;

[0181] ;

[0182] ;

[0183] Step 9: The transmitting module modulates the baseband interference signal into a radio frequency interference signal, and transmits the radio frequency interference signal to the SAR or a designated ground area within a corresponding time period according to the instruction of the timing control module, including:

[0184] Step 9.1, the timing control module calculates the The emission window start time of each pulse and launch window time period :

[0185] ;

[0186] ;

[0187] in, is the emission window length, symbol It means finding the difference of two sets.

[0188] Step 9.2, the transmitter module transmits the baseband interference signal Up-convert and perform digital-to-analog conversion, modulate into RF interference signal, and transmit in the transmission window time period Transmit radio frequency interference signals into SAR or designated ground areas.

[0189] It should be noted that steps 5 to 9 are executed once for each frame of SAR signal, and are executed cyclically until the interference stops (the cycle stops when the number of cycles reaches a preset value).

[0190] Example:

[0191] The embodiment of the present invention provides an example of a SAR image obtained by jamming an airborne SAR using the method and jammer provided by the present invention. For comparison purposes, the embodiment of the present invention also provides a SAR image of the same area before the jamming.

[0192] Figure 3 is the SAR image of area 1 acquired by the airborne SAR before the interference. Figure 4 The method and jammer provided by the present invention are used to jam airborne SAR in a false target implantation mode to obtain a SAR image of area one. Figure 5 The method and jammer provided by the present invention are used to jam an airborne SAR in a pseudo radio frequency jamming mode to obtain a SAR image of area one. Figure 6 This is the SAR image of area 2 acquired by the airborne SAR before the interference. Figure 7 In order to obtain the SAR image of area 2 after interfering with the airborne SAR in the scattered wave interference mode using the method and jammer provided by the present invention, the scattering area in this experiment is the three trees in the center of area 2.

[0193] like Figure 3 As shown in Figure 1, before the interference, the ground objects in the SAR image of area 1 are clearly visible. Figure 4 As shown in the figure, after being interfered by the false target implantation, a false target in the shape of a crosshair appeared in area 1 ( Figure 4 In the example above, the white circle is part of the crosshairs, which is also part of the false target. The false target (crosshairs) is the circle and the cross with scale inside it. Figure 5 As shown in the figure, after being subjected to pseudo-RF interference, a large area of interference similar to unintentional RF interference appeared in area 1, and the ground objects covered by the interference were no longer clear (became Figure 5 striped image). Figure 6 As shown in Figure 2, before the interference, the ground objects in the SAR image of area 2 are clearly visible. Figure 7 As shown in Figure 1, after being disturbed by the scattered waves, the ghost images of the three trees in the scattering area appear in area 2.

[0194] The present invention also provides an electronic device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of the multi-mode SAR interference method when executing the program.

[0195] The present invention also provides a non-transitory computer-readable storage medium having a computer program stored thereon. When the computer program is executed by a processor, the steps of the multi-mode SAR interference method are implemented.

[0196] Those skilled in the art will appreciate that embodiments of the present invention may be provided as methods, systems, or computer program products. Thus, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk drives, CD-ROMs, optical storage devices, etc.) containing computer-usable program code. The solutions in the embodiments of the present invention may be implemented using various computer languages, such as the object-oriented programming language Java and the interpreted scripting language JavaScript.

[0197] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowcharts and / or block diagrams, as well as combinations of processes and / or blocks in the flowcharts and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowcharts and / or block diagrams. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0198] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0199] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0200] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0201] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.

Claims

1. A multi-mode SAR jamming method, characterized in that: include: In the jamming preparation phase, the product matrices of the false target implantation pattern, the pseudo radio frequency jamming pattern and the scattered wave jamming pattern are calculated respectively; After entering the reconnaissance phase, intercept the first segment of the received signal; Determine whether the first segment of the received signal is a SAR signal, estimate the parameters of the SAR signal, and extract a complete frame of the SAR pulse signal as a reference signal; Intercept the second segment of the received signal and determine whether it has entered the interference stage based on the PRF; PRF denotes pulse repetition frequency; After entering the jamming phase, some SAR pulse signals are received according to the timing control; Restoring a partial SAR pulse signal to a complete SAR pulse signal; Multiplying the complete SAR pulse signal with the product matrix of the selected false target implantation pattern, pseudo radio frequency interference pattern or scattered wave interference pattern to obtain a preliminary modulated interference signal; Performing Doppler phase modulation and time delay modulation on the initially modulated interference signal to obtain a baseband interference signal; The baseband interference signal is modulated into a radio frequency interference signal, and the radio frequency interference signal is transmitted to the SAR or a designated ground area within a corresponding time period.

2. A multi-mode SAR jamming method according to claim 1, characterized in that: In the jamming preparation phase, the product matrices of the false target implantation pattern, pseudo RF jamming pattern, and scattered wave jamming pattern are calculated respectively, including: Calculate the product matrix of the false target implantation pattern ; Calculate the product matrix of the pseudo RFI pattern ; Calculate the product matrix of the scattered wave interference pattern ; The jammer loads the corresponding product matrix according to the jamming mode selected by the user.

3. A multi-mode SAR jamming method according to claim 2, characterized in that: Calculate the product matrix of the false target implantation pattern include: Perform azimuth interpolation and zero padding on each column vector of the false target pattern matrix, and then concatenate the zero-padded column vectors to obtain the matrix ; Pair Matrix Divide the blocks into azimuths and calculate the corresponding product matrices ,in is the serial number of the block matrix; Accumulate the product matrices corresponding to all blocks , get the product matrix of the false target implantation pattern .

4. A multi-mode SAR jamming method according to claim 3, characterized in that: Pair Matrix Divide the blocks into azimuths and calculate the corresponding product matrices include: Pair Matrix Perform azimuth block division to obtain the block matrix ; The block matrix is interpolated and filled with zeros Mapped to the two-dimensional time domain, we get the matrix ; Pair Matrix Perform inverse fast Fourier transform on each column of ; Pair Matrix Each column of compensates the Doppler modulation frequency relative to the center of the interference pattern, and the matrix ; Pair Matrix Perform inverse fast Fourier transform on each row of ; Pair Matrix Compensate for the distance migration relative to the center of the interference pattern and calculate the product matrix .

5. A multi-mode SAR jamming method according to claim 4, characterized in that: Calculate the product matrix of the pseudo RFI pattern include: Calculate the time mask matrix of pseudo-RF interference ; The time mask matrix of pseudo-RF interference Multiply the distance frequency signal and the linear frequency modulation signal to get the matrix : ； Among them, exp is the exponential function, j represents the imaginary unit, represents pi, is the frequency shift column vector, represents the distance-to-time row vector, is the column vector of range frequency modulation compensation, represents the Hadamard product of matrices; The matrix Multiply the low-frequency noise in the distance direction to get the matrix : ； in, Indicates 1 line A matrix with all 1s in its columns, is the number of rows of the preset product matrix, is the noise row vector; The matrix Multiplied by the azimuth low-frequency noise and linear frequency modulation signal, the product matrix is the RF interference pattern : ； in, is the noise column vector, which has been low-pass filtered in azimuth. Indicates 1 line A matrix with all 1s in its columns, is the number of columns of the preset product matrix, and the superscript T represents the transpose of the matrix. is the Doppler modulation frequency of the azimuth linear frequency modulation signal, is the azimuthal time column vector.

6. A multi-mode SAR jamming method according to claim 5, characterized in that: Calculate the time mask matrix of pseudo-RF interference include: Generate a two-dimensional time matrix according to the following formula : ； The time mask matrix of pseudo-RF interference is calculated as follows The value of each element of : ； in, is a matrix The cth row and dth column element, mod represents the remainder function, is a matrix The element in row c and column d of is the pulse repetition period of the pseudo-RF interference, is the pulse duration of the spurious RFI.

7. A multi-mode SAR jamming method according to claim 6, characterized in that: Calculate the product matrix of the scattered wave interference pattern include: Set up interference areas, including a main interference area and Additional interference areas; set the range coordinates and azimuth coordinates of the center of each interference area, and calculate the real-time distance from the center of the main interference area to the SAR based on the track or orbit parameters of the SAR platform , and the real-time distance from the center of each additional interference area to the SAR , is the serial number of the additional interference area; and Both Column vector of rows, each row corresponds to an azimuth time; According to the real-time distance from the center of the main interference area to the SAR And the real-time distance from the center of each additional interference area to the SAR , calculate the Doppler phase difference and time delay of the additional interference area relative to the main interference area, and obtain the product matrix of the scattered wave interference pattern : ； in, is the speed of light, is the modulation frequency of the SAR signal, is the wavelength of SAR.

8. The multi-mode SAR jamming method according to claim 1, wherein: After entering the jamming phase, the following steps are performed to receive part of the SAR pulse signal according to the timing control: Calculate the following formula The start time of the receiving window of the pulse : ； in, is the pulse number, It is The start time of the receiving window of a pulse, is the pulse repetition frequency, The first The frequency difference of the partial SAR pulse signal relative to the reference signal; The electromagnetic signal within the receiving frequency band is down-converted and digitally sampled to obtain a digital signal, and the The digital signal within the time period is used as a partial SAR pulse signal, where is the receive window length.

9. The multi-mode SAR jamming method according to claim 8, characterized in that: Modulating the baseband interference signal into a radio frequency interference signal and transmitting the radio frequency interference signal to the SAR or a designated ground area within a corresponding time period includes: Calculate the following formula The emission window start time of each pulse and launch window time period : ； ； in, is the integer sampling point partial delay to be modulated, is the emission window length, symbol It means finding the difference between two sets; The baseband interference signal is up-converted and converted into digital-to-analog form, modulated into a radio frequency interference signal, and then transmitted to the SAR or a designated ground area within the transmission window.

10. A multi-mode SAR jammer, characterized in that: include: A receiving antenna is used to convert the electromagnetic waves emitted by the SAR propagating in space into electromagnetic signals on the transmission line; The transmitting antenna is used to convert the radio frequency interference signal on the transmission line into an electromagnetic wave radiated in a specified direction; when the selected interference mode is the false target implantation mode or the pseudo radio frequency interference mode, the antenna points to the SAR; When the selected interference mode is the scattered wave interference mode, the antenna points to the ground scattering area; The timing control module is used to calculate the receiving time window of the SAR signal and the transmitting time window of the interference signal, and send control instructions to the receiving module and the transmitting module; The receiving module is used to down-convert the electromagnetic signal within the receiving frequency band and sample it to obtain a digital signal. In the reconnaissance phase, it provides the first segment of the received signal and the second segment of the received signal to the SAR signal recognition and parameter estimation module. In the interference phase, it provides part of the SAR pulse signal to the pulse recovery module. The SAR signal identification and parameter estimation module is used to determine whether the received signal is a SAR signal and estimate the parameters of the SAR signal. It extracts a complete frame of SAR pulse signal as a reference signal, provides the PRF estimation value of the SAR signal to the timing control module, and provides the modulation frequency estimation value and reference signal of the SAR signal to the pulse recovery module. PRF stands for pulse repetition frequency. The pulse recovery module is used to restore the partial SAR pulse signal to a complete SAR pulse signal, provide the receiving window start correction information to the timing control module, and provide the complete SAR pulse signal to the product modulation module; A product modulation module is used to multiply the complete SAR pulse signal with the product matrix of the selected false target implantation pattern, pseudo radio frequency interference pattern or scattered wave interference pattern to obtain a preliminary modulated interference signal, and provide the preliminary modulated interference signal to the central modulation module; The central modulation module is used to perform Doppler phase modulation and time delay modulation on the initially modulated interference signal, change the center position of the interference pattern, obtain a baseband interference signal, and provide the baseband interference signal to the transmission module; The transmitting module is used to up-convert the baseband interference signal and perform digital-to-analog conversion to obtain the radio frequency interference signal, and output the radio frequency interference signal to the transmitting antenna.

11. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein: When the processor executes the program, the steps of the multi-mode SAR interference method according to any one of claims 1 to 9 are implemented.

12. A non-transitory computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the multi-mode SAR interference method according to any one of claims 1 to 9 are implemented.

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