A method and system for realizing two-dimensional sinusoidal frequency modulation regional controllable SAR interference

Abstract

The present invention discloses a method and system for realizing two-dimensional sinusoidal frequency modulation regional controllable SAR interference, which belongs to the field of radar interference technology; the method comprises: performing down-conversion processing on the received radar signal; inputting the obtained intermediate frequency signal into the FPGA, and performing the following processing: performing ADC sampling on the intermediate frequency signal to obtain a multi-channel digital signal; performing calculation based on the multi-channel digital signal and the preset interference parameters, using the DDS IP core to generate the range and azimuth interference to generate a two-dimensional sinusoidal frequency modulation forwarding interference signal; converting the two-dimensional sinusoidal frequency modulation forwarding interference signal into an analog signal; after performing up-conversion processing on the analog signal, it is sent out through the transmitting antenna, so that the SAR receives the echo and forms a two-dimensional interference signal when the echo is coherently accumulated. The method realizes the accurate control of the interference range in the azimuth and range directions by adjusting the preset interference parameters, and solves the problem of controlling the interference intensity within the determined interference range.

Description

Technical Field

[0001] The present invention belongs to the technical field of radar jamming, and in particular relates to a method for implementing two-dimensional sinusoidal frequency modulation area controllable SAR (Synthetic Aperture Radar) jamming. Background Art

[0002] Synthetic aperture radar (SAR), with its high resolution, strong penetration, excellent anti-interference capabilities, and all-weather operation, is widely used in Earth observation, military surveillance, and intelligence gathering. SAR is playing an increasingly important role in electronic countermeasures. Interfering with SAR to protect friendly targets has become a crucial issue in modern military operations.

[0003] Interference to SAR can be categorized from different perspectives. Based on the energy source of the interference signal, it can be divided into two main types: active interference and passive interference. Active interference, with its diverse modulation methods, complex and variable interference patterns, and considerable initiative, is currently the mainstream direction of interference development. Based on the interference effect, active interference can be divided into deception and suppression. Deception aims to conceal the truth and show false information, tricking the radar into "detecting" false target information, while suppression aims to mask important target information. Based on the coherence of the interference signal with the radar signal, active interference can be divided into coherent interference, partially coherent interference, and incoherent interference. Coherent interference has a high interference energy utilization rate, but requires a high level of radar signal detection and interference signal processing. Incoherent interference generally only requires information about the radar's carrier frequency and bandwidth, requiring less processing for both detection and interference signals. Partially coherent interference has an energy utilization rate and requirements for both detection and interference signal processing that fall somewhere in between.

[0004] Currently, forward jamming is one of the most commonly used jamming methods in the field. Pulse-by-pulse forwarding creates a point target for SAR, but signal modulation is necessary to achieve large-area coverage. One-dimensional cosine phase modulation forwarding jamming can create linear decoy strings. Two-dimensional cosine phase modulation jamming, by forwarding SAR signals with modulated cosine phase, spreads the SAR echoes in pairs in the range frequency domain and the azimuth Doppler domain. After pulse compression processing, the linear frequency modulation signal can form evenly spaced targets, achieving multi-target jamming of SAR. By flexibly setting jamming modulation parameters, various jamming effects can be achieved, such as compact area decoys and grid-like decoy strings, effectively shielding distributed important targets. Two-dimensional cosine phase modulation-based effective suppression area expansion jamming, based on two-dimensional cosine phase modulation jamming, uses intermittent sampling in azimuth to extend the azimuth jamming range, while frequency shifting in range effectively expands the range jamming range. Two-dimensional cosine phase modulation-based secondary modulation jamming uses a single two-dimensional cosine phase modulation as the generated sample, which is then subjected to a second one-dimensional or two-dimensional cosine phase modulation. The size of the false target generated by this method can be set as needed, and can present different interference effects as suppression interference.

[0005] However, both the existing two-dimensional cosine phase modulation interference and the two-dimensional extended interference with effective suppression area based on two-dimensional cosine phase modulation find it difficult to control the interference intensity within a certain interference range; the interference method based on two-dimensional cosine phase modulation secondary modulation, the generated interference range can be set according to needs, but the secondary modulation based on two-dimensional interference increases the complexity of interference implementation, which is not conducive to engineering implementation. Summary of the Invention

[0006] In order to solve the above problems existing in the prior art, the present invention provides a method and system for implementing two-dimensional sinusoidal frequency modulation regional controllable SAR jamming. The technical problem to be solved by the present invention is achieved through the following technical solutions:

[0007] In a first aspect, the present invention proposes a method for implementing two-dimensional sinusoidal frequency modulation regional controllable SAR interference, comprising:

[0008] Step 1: Down-convert the received radar signal to obtain an intermediate frequency signal;

[0009] Step 2: Input the IF signal into the FPGA (Field Programmable Gate Array) for the following processing:

[0010] Perform ADC sampling on the intermediate frequency signal to obtain multiple digital signals;

[0011] Based on multiple digital signals and preset interference parameters, calculations are performed and a DDS (Direct Digital Synthesizer) IP (Intellectual Property) core is used to generate range and azimuth interference, thereby generating a two-dimensional sinusoidal frequency-modulated forwarding interference signal.

[0012] Converting a two-dimensional sinusoidal frequency-modulated repeater interference signal into an analog signal;

[0013] Step 3: After up-converting the analog signal, it is sent out through the transmitting antenna so that the SAR receives the echo and performs coherent accumulation to form a two-dimensional interference signal.

[0014] In a second aspect, the present invention proposes a two-dimensional sinusoidal frequency modulation regional controllable SAR interference implementation system for implementing the method proposed in the first aspect of the present invention. The system includes a receiving antenna, a microwave board, an ADC signal acquisition module, an FPGA digital signal processing board, a host computer, a DAC digital-to-analog conversion module, and a transmitting antenna; wherein,

[0015] The receiving antenna is used to receive radar signals;

[0016] The microwave board is used to down-convert the received radar signal to obtain an intermediate frequency signal;

[0017] The ADC signal acquisition module is used to perform ADC sampling on the intermediate frequency signal to obtain multiple digital signals;

[0018] The FPGA digital signal processing board is used to perform calculations based on multi-channel digital signals and preset interference parameters, and uses the DDS IP core to generate range and azimuth interference, thereby generating a two-dimensional sinusoidal frequency modulation forwarding interference signal;

[0019] The host computer is used to provide preset interference parameters to the FPGA digital signal processing board;

[0020] The DAC digital-to-analog conversion module is used to convert the two-dimensional sinusoidal frequency modulation forwarding interference signal into an analog signal;

[0021] The microwave board is also used to up-convert analog signals;

[0022] The transmitting antenna is used to transmit the signal after frequency conversion processing so that the SAR can form a two-dimensional interference signal when receiving the echo and performing coherent accumulation.

[0023] Beneficial effects of the present invention:

[0024] The present invention provides a method for implementing two-dimensional sinusoidal frequency-modulated regionally controllable SAR jamming. First, the received radar signal is down-converted. The resulting intermediate frequency signal is then input into an FPGA for the following processing: ADC sampling of the intermediate frequency signal produces a multi-channel digital signal. Based on the multi-channel digital signal and preset interference parameters, calculations are performed using a DDS IP core to generate range and azimuth interference, thereby generating a two-dimensional sinusoidal frequency-modulated forwarding jamming signal. The two-dimensional sinusoidal frequency-modulated forwarding jamming signal is converted into an analog signal. Finally, the analog signal is up-converted and transmitted through a transmitting antenna so that the coherent accumulation of SAR received echoes forms a two-dimensional jamming signal. This method accurately controls the azimuth and range interference ranges by adjusting the interference parameters input to the FPGA. This method also effectively addresses the issue of controlling the interference intensity within a defined interference range, thus achieving two-dimensional sinusoidal frequency-modulated regionally controllable SAR jamming. Furthermore, this method utilizes a multi-channel parallel DDS IP core in the FPGA to generate the jamming signal, addressing the issue of limited data generation in existing multi-channel parallel signal generation modules. This method offers greater flexibility, improved system performance and operability, and facilitates engineering implementation.

[0025] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a flow chart of a method for implementing two-dimensional sinusoidal frequency modulation regionally controllable SAR interference provided by an embodiment of the present invention;

[0027] Figure 2 This is a flow chart of another method for implementing two-dimensional sinusoidal frequency modulation regionally controllable SAR interference provided by an embodiment of the present invention;

[0028] Figure 3 This is a schematic diagram of a process for generating a two-dimensional sinusoidal frequency modulation forwarding interference signal in an FPGA according to an embodiment of the present invention;

[0029] Figure 4 This is a schematic diagram of the operating principle of an 8-channel parallel DDS IP core generating an interference signal provided by an embodiment of the present invention;

[0030] Figure 5 This is a schematic diagram of the output effect of the 8-channel parallel DDS IP core provided by an embodiment of the present invention;

[0031] Figure 6 This is an actual test diagram of the BLOCKRAM resource usage of the 8-channel parallel DDS IP core provided by an embodiment of the present invention;

[0032] Figure 7This is a structural block diagram of a two-dimensional sinusoidal frequency modulation regional controllable SAR interference implementation system provided by an embodiment of the present invention;

[0033] Figure 8 This is a hardware design diagram of a two-dimensional sinusoidal frequency modulation regional controllable SAR jamming implementation system provided by an embodiment of the present invention;

[0034] Figure 9 This is the MATLAB frequency domain diagram of the DAC output data when the range interference modulation coefficient is 4 in the simulation experiment;

[0035] Figure 10 This is the MATLAB frequency domain diagram of the DAC output data when the range interference modulation coefficient is 100 in the simulation experiment;

[0036] Figure 11 It is the imaging result of the original data of spaceborne SAR in the simulation experiment;

[0037] Figure 12 This is the imaging result after implementing two-dimensional sinusoidal frequency modulation regional controllable interference in the simulation experiment when the range interference modulation coefficient is 100, the range interference range is 1km, the azimuth interference modulation coefficient is 100, and the azimuth interference range is 1km;

[0038] Figure 13 This is the imaging result after implementing two-dimensional sinusoidal frequency modulation regional controllable interference in the simulation experiment when the range interference modulation coefficient is 4, the range interference range is 1km, the azimuth interference modulation coefficient is 2, and the azimuth interference range is 1km;

[0039] Figure 14 This is the imaging result after implementing two-dimensional sinusoidal frequency modulation regional controllable interference in the simulation experiment when the range interference modulation coefficient is 100, the range interference range is 5km, the azimuth interference modulation coefficient is 100, and the azimuth interference range is 10km;

[0040] Figure 15 This is the imaging result after implementing two-dimensional sinusoidal frequency modulation regional controllable interference in the simulation experiment when the range interference modulation coefficient is 4, the range interference range is 5km, the azimuth interference modulation coefficient is 2, and the azimuth interference range is 10km. DETAILED DESCRIPTION

[0041] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0042] The first aspect of the present invention provides a method for implementing two-dimensional sinusoidal frequency modulation regional controllable SAR interference. Figure 1 and Figure 2 , Figure 1 1 is a flow chart of a method for implementing two-dimensional sinusoidal frequency modulation regionally controllable SAR interference provided by an embodiment of the present invention. Figure 2 1 is a flow chart of another method for implementing two-dimensional sinusoidal frequency modulation regional controllable SAR interference provided by an embodiment of the present invention. The method for implementing two-dimensional sinusoidal frequency modulation regional controllable SAR interference provided by the present invention mainly includes the following steps:

[0043] Step 1: Down-convert the received radar signal to obtain an intermediate frequency signal.

[0044] In this embodiment, after the radar signal is received by the receiving antenna, the radar signal may be down-converted using the microwave board to obtain a radar intermediate frequency signal.

[0045] Step 2: Input the intermediate frequency signal into the FPGA and perform the following processing:

[0046] 21) Perform ADC sampling on the intermediate frequency signal to obtain multiple digital signals.

[0047] Optionally, as an implementation manner, the multi-channel digital signals obtained by ADC sampling in this embodiment can be 8-channel 12-bit digital signals, that is, 8-channel real parts of radar intermediate frequency signals.

[0048] 22) Based on the multi-channel digital signals and the preset interference parameters, the DDS IP core is used to generate the range and azimuth interference, thereby generating a two-dimensional sinusoidal frequency modulation forwarding interference signal.

[0049] 22a) Detect multiple digital signals and obtain effective radar pulse signals.

[0050] It is understandable that after the FPGA, it is necessary to first detect and process the multi-channel digital signals to obtain the signal's carrier frequency, pulse width, bandwidth and other information. At the same time, through envelope detection, the radar pulse effective signal can also be obtained. Furthermore, the radar range modulation frequency can be obtained by dividing the bandwidth by the pulse width. , using the speed of light Dividing by the carrier frequency can also give the carrier wavelength This information is then used to perform calculations to generate interference signals in range and azimuth.

[0051] 22b) Based on the radar pulse valid signal and the preset range interference parameters, the DDS IP core is used to generate the range interference signal.

[0052] Specifically, in FPGA, the rising and falling edges of the effective radar pulse signal are extracted. When the rising edge is triggered, the distance to fast time counting starts, and when the falling edge is triggered, it ends. That is, the distance to fast time records the number of sampling points in the pulse. The intermediate frequency range interference signal is expressed as:

[0053] ;

[0054] in, is the distance sinusoidal modulation frequency, is the range interference modulation coefficient, is the amplitude coefficient, is the frequency modulation of the interference signal. According to the Carson formula, the effective bandwidth of the range interference is:

[0055] .

[0056] Obviously, as the interference modulation coefficient increases, the effective interference bandwidth also increases. times, the number of false targets is According to the frequency shift principle, the distance between adjacent false targets is for:

[0057] ;

[0058] in, is the speed of light, is the radar range modulation frequency, so the range interference range is:

[0059] .

[0060] Optionally, since the ADC sampling signal in this embodiment is an 8-channel 12-bit digital signal, that is, the real part of the 8-channel radar intermediate frequency signal, the range interference signal that needs to be generated is also an 8-channel real signal. In this embodiment, a multi-channel parallel DDS IP core is used to generate the range interference signal, and the number of channels is set to 8, which can be understood as an 8-channel parallel DDS IP core signal generation module.

[0061] For details, see Figure 3 , Figure 3 This is a flow chart of generating a two-dimensional sinusoidal frequency modulation forwarding interference signal in an FPGA according to an embodiment of the present invention, wherein the specific method of generating the range interference signal is shown in the following steps S101-S103.

[0062] S101, according to the preset distance to the interference range and range interference modulation coefficient , use the FPGA internal divider IP core and multiplier IP core to calculate the distance to the adjacent false target interval and range modulation frequency , the calculation formula is:

[0063] ;

[0064] The preset parameters can be configured from the host computer to the FPGA and can be adjusted according to actual needs.

[0065] S102, modulate frequency according to distance and range interference modulation coefficient , calculate the range frequency control word.

[0066] As can be seen from the previous text, the expression of the intermediate frequency range interference signal is:

[0067] ;

[0068] Then the phase function of the intermediate frequency range interference signal can be obtained as:

[0069] ;

[0070] The frequency function can be obtained by differentiating the phase function:

[0071] .

[0072] It is understandable that if 8-way IF range interference real signals are obtained through the 8-channel parallel DDS IP core signal generation module, the IF range interference signal frequency control word must be obtained. The expected output signal frequency of the 8-channel parallel DDS IP core signal generation module is:

[0073] ;

[0074] DDS IP core frequency control word and output frequency The relationship is:

[0075] ;

[0076] in, Input control word width for DDS IP core, It is the working clock of DDS IP core. is the output signal frequency.

[0077] The frequency control word of the intermediate frequency range interference signal can be designed as:

[0078] ;

[0079] in, This is the frequency control word width of the DDS IP core in the 8-channel parallel DDS IP core signal generation module.

[0080] Furthermore, to calculate in FPGA First, you need to instantiate a single DDS IP core to generate Cosine signal, the expected frequency of the cosine signal output by a single DDS IP core is Similarly, based on the relationship between the DDS IP core frequency control word and the output frequency, the frequency control word of a single DDS IP core is designed:

[0081] ;

[0082] That is, the distance frequency control word of a single DDS IP core is:

[0083] ;

[0084] in Input control word width for a single DDS IP core, It is the working clock of DDS IP core. is the frequency of the output signal in the distance direction. After getting a single DDS IP core, you can get Cosine signal.

[0085] Get the cosine signal Then, use the Multiplier IP core three times to achieve Multiply by the range modulation frequency , then multiplied by the range modulation coefficient , and finally multiply by , we can get the frequency control word of the intermediate frequency range interference signal .

[0086] S103 , inputting the range frequency control word into the multi-channel parallel DDS IP core to generate multi-channel parallel range interference signals.

[0087] Specifically, based on the relationship between the frequency control word and the phase control word of the DDS IP core and the signal generation principle of the DDS IP core, a multi-channel parallel DDS IP core is designed in this embodiment to generate an interference signal, which is expressed as:

[0088] ;

[0089] Where, Indicates channel The azimuth interference signal generated, Indicates the channel number; Indicates the total number of channels.

[0090] Optional, take 8 channels as an example, see Figure 4 , Figure 4 This is a schematic diagram of the operating principle of the 8-channel parallel DDS IP core provided by the embodiment of the present invention. Among them, the frequency control words of the 8 instantiated DDS IP cores are the same; the phase control word uses a differential input method that increases step by step, that is, the phase control word is Increment to , the phase control word step is The multi-channel parallel signal generation module outputs 8 real signals, namely 8 cosine signals:

[0091] .

[0092] Further, Figure 5 The output effect diagram of the 8-channel parallel DDS IP core is shown. Assume that the frequency of the signal generated by the input 8-channel parallel DDS IP core is , output 8 real signals, The serial arrangement outputs a frequency of The cosine signal.

[0093] In existing multi-channel parallel signal generation modules, a DDS IP core is instantiated once to generate a single signal. This signal is then converted into multiple signals using a channel conversion module. Although the DDS IP core is only used once, the channel conversion module requires a large amount of RAM for storage and read operations. Converting one signal into eight signals requires instantiation of 16 RAM IP cores. The more signal conversion channels there are, the more RAM IP cores need to be instantiated, increasing the FPGA's block RAM resource utilization. Furthermore, RAM storage depth is limited, so the amount of data generated by channel conversion to generate multiple parallel signals is also limited by the RAM storage depth.

[0094] The present invention is designed as Figure 4 The 8-channel parallel DDS IP core shown generates interference signals and does not use data storage and reading IP cores such as RAM. There is no limit on the amount of data generated, and the BLOCKRAM occupancy rate is low. Figure 6This test diagram shows the actual BLOCKRAM resource usage of the 8-channel parallel DDS IP core. The signal generation module instance of the 8-channel parallel DDS IP core, named Distance_SIGNAL, uses 16 blocks of RAM, while each DDS IP core channel uses only 2 blocks of RAM. For radar signals with large pulse widths and a large number of ADC sampling points, the 8-channel parallel DDS IP core demonstrates lower resource utilization, providing greater applicability and flexibility.

[0095] 22c) Based on the radar pulse valid signal and the preset azimuth interference parameters, the DDS IP core is used to generate the azimuth interference signal.

[0096] In FPGA, the rising edge of the pulse valid enable signal is extracted, and the azimuth slow time counting starts when the rising edge arrives, that is, the azimuth slow time records the number of pulses The expression of the intermediate frequency azimuth interference signal is:

[0097] ;

[0098] Where, is the azimuth sinusoidal frequency, is the azimuth modulation coefficient. According to the Carson formula, the effective bandwidth of the azimuth interference is:

[0099] ;

[0100] Forwarding interference signal spectrum times, the number of false targets formed is According to the frequency shift principle, the interval between adjacent false targets in azimuth is for:

[0101] ;

[0102] in, represents the carrier wavelength, Indicates the center slope distance, represents the flight speed of the SAR platform, so the interference range in azimuth is:

[0103] .

[0104] Similarly, since the ADC sampling signal is 8-channel 12-bit digital signals, the azimuth interference signal only needs to generate 8-channel real signals.

[0105] Please continue to see Figure 3 , the specific method of generating the azimuth interference signal refers to the following steps S201-S203.

[0106] S201, according to the preset azimuth interference range and azimuth interference modulation coefficient , use the FPGA internal divider IP core and multiplier IP core to calculate the azimuth interval between adjacent false targets and azimuth modulation frequency , the calculation formula is as follows:

[0107] ;

[0108] Where, Indicates the flight speed of the SAR platform; Indicates the carrier wavelength; Indicates the center slant distance. These parameters can be configured from the host computer to the FPGA and can be adjusted according to actual conditions.

[0109] S202, modulate frequency according to azimuth , SAR platform flight speed and center slope distance Calculate the azimuth frequency control word.

[0110] As we can see from the previous text, the expression of the intermediate frequency azimuth interference signal is:

[0111] ;

[0112] Then the phase function of the intermediate frequency azimuth interference signal can be obtained as:

[0113] ;

[0114] The frequency function can be obtained by differentiating the phase function:

[0115] ;

[0116] Where, is the radar signal pulse width, is the radar signal pulse repetition period, the distance to fast time Record the number of sampling points in the pulse and the azimuth slow time Record the number of pulses, Count from 0 to , Each count is increased by 1, and the count relationship is mapped to the timing of the interference signal. The number of digital signal points generating distance interference is At this time, only one interference digital signal is generated in the azimuth direction.

[0117] Using the rising edge trigger of the radar pulse valid signal as the valid condition of the DDS IP core control word input, the generated one-way azimuth interference signal is copied into eight parallel signals, which can meet the timing and number requirements of the azimuth interference signal.

[0118] Specifically, a single DDS IP core is instantiated to generate a single intermediate frequency azimuth interference signal. The expected output signal frequency is:

[0119] ;

[0120] The relationship between the DDS IP core frequency control word and output frequency is:

[0121] ;

[0122] in, Input control word width for DDS IP core, It is the working clock of DDS IP core. is the output signal frequency.

[0123] The frequency control word of the intermediate frequency azimuth interference signal can be designed as:

[0124] ;

[0125] in, The frequency control word width of a single DDS IP core.

[0126] Furthermore, to calculate in FPGA First, you need to instantiate a single DDS IP core to generate Cosine signal, the expected frequency of the cosine signal output by a single DDS IP core is Similarly, based on the relationship between the DDS IP core frequency control word and the output frequency, the frequency control word of a single DDS IP core is designed:

[0127] ;

[0128] That is, the azimuth frequency control word of a single DDS IP core is:

[0129] ;

[0130] in, Input control word width for a single DDS IP core, It is the working clock of DDS IP core. is the azimuth output signal frequency. Input After getting a single DDS IP core, you can get Cosine signal.

[0131] Get the cosine signal Then, use the Multiplier IP core three times to achieve Multiply by the range modulation frequency , then multiplied by the range modulation coefficient , and finally multiply by , we can get the frequency control word of the intermediate frequency azimuth interference signal .

[0132] S203 , inputting the azimuth frequency control word into a single DDS IP core to generate one azimuth interference signal, and duplicating it into multiple parallel signals to obtain multiple parallel azimuth interference signals.

[0133] Specifically, the azimuth frequency control word is used as the frequency control word of a single DDS, and the rising edge trigger of the radar pulse valid signal is used as the valid condition of the DDS IP core control word input. An azimuth interference signal is generated and copied into 8 parallel signals to obtain 8 parallel azimuth interference signals.

[0134] 22d) Multiplying the range interference signal, the azimuth interference signal, and the multi-channel digital signal to generate a two-dimensional sinusoidal frequency modulation forwarding interference signal.

[0135] Specifically, according to the generation process of the range interference signal in S101-S103 and the azimuth interference signal in S201-S203, the two exist independently and do not affect each other. Suppose the radar signal sampled by the ADC is , then the two-dimensional sinusoidal FM forwarding interference signal is:

[0136] ;

[0137] Finally, the 8-way ADC samples the signal 8-way distance interference signal 8-way azimuth interference signals to generate interference signals.

[0138] Since the interference pattern implemented in this embodiment is two-dimensional coherent interference, the interference signal can obtain a processing gain equivalent to that of the transmitted signal, so the interference power required is smaller than that of the traditional FPGA-based interference suppression.

[0139] 23) Convert the two-dimensional sinusoidal FM repeater interference signal into an analog signal.

[0140] Specifically, the generated two-dimensional sinusoidal frequency modulation forwarding interference signal is converted into an analog signal output through an 8-channel DAC.

[0141] Step 3: After up-converting the analog signal, it is sent out through the transmitting antenna so that a two-dimensional interference signal is formed when the SAR receives the echo and performs coherent accumulation.

[0142] Specifically, the analog signal can be up-converted using a microwave board and then transmitted through a transmitting antenna, so that a two-dimensional interference signal can be formed when the SAR receives the echo and performs coherent accumulation.

[0143] The present invention provides a method for implementing two-dimensional sinusoidal frequency-modulated regionally controllable SAR jamming. First, the received radar signal is down-converted. The resulting intermediate frequency signal is then input into an FPGA for the following processing: ADC sampling of the intermediate frequency signal produces a multi-channel digital signal. Based on the multi-channel digital signal and preset interference parameters, calculations are performed using a DDS IP core to generate range and azimuth interference, thereby generating a two-dimensional sinusoidal frequency-modulated forwarding jamming signal. The two-dimensional sinusoidal frequency-modulated forwarding jamming signal is converted into an analog signal. Finally, the analog signal is up-converted and transmitted through a transmitting antenna so that the coherent accumulation of SAR received echoes forms a two-dimensional jamming signal. This method accurately controls the azimuth and range interference ranges by adjusting the interference parameters input to the FPGA. This method also effectively addresses the issue of controlling the interference intensity within a defined interference range, thus achieving two-dimensional sinusoidal frequency-modulated regionally controllable SAR jamming. Furthermore, this method utilizes a multi-channel parallel DDS IP core in the FPGA to generate the jamming signal, addressing the issue of limited data generation in existing multi-channel parallel signal generation modules. This method offers greater flexibility, improved system performance and operability, and facilitates engineering implementation.

[0144] Based on the same inventive concept, the second aspect of the present invention provides a two-dimensional sinusoidal frequency modulation regional controllable SAR interference implementation system. Figure 7 , Figure 7 This is a block diagram of a two-dimensional sinusoidal frequency modulation regional controllable SAR jamming implementation system provided by an embodiment of the present invention. The system includes: a receiving antenna, a microwave board, an ADC signal acquisition module, an FPGA digital signal processing board, a host computer, a DAC digital-to-analog conversion module, and a transmitting antenna; wherein,

[0145] The receiving antenna is used to receive radar signals;

[0146] The microwave board is used to down-convert the received radar signal to obtain an intermediate frequency signal;

[0147] The ADC signal acquisition module is used to perform ADC sampling on the intermediate frequency signal to obtain multiple digital signals;

[0148] The FPGA digital signal processing board is used to perform calculations based on multi-channel digital signals and preset interference parameters, and uses the DDS IP core to generate range and azimuth interference, thereby generating a two-dimensional sinusoidal frequency modulation forwarding interference signal;

[0149] The host computer is used to provide preset interference parameters to the FPGA digital signal processing board;

[0150] The DAC digital-to-analog conversion module is used to convert the two-dimensional sinusoidal frequency modulation forwarding interference signal into an analog signal;

[0151] The microwave board is also used to up-convert analog signals;

[0152] The transmitting antenna is used to transmit the signal after frequency conversion processing so that the SAR can form a two-dimensional interference signal when receiving the echo and performing coherent accumulation.

[0153] Optionally, as an implementation, Figure 8 This is a hardware design diagram for a two-dimensional sinusoidal frequency-modulated regionally controllable SAR jammer implementation system provided by an embodiment of the present invention. In this embodiment, the ADC signal acquisition module can be implemented using the ADC12DJ3200, the FPGA digital signal processing board can be implemented using the XCU13P-2FHGB2104I, and the DAC digital-to-analog conversion module can be implemented using the AD9164.

[0154] It is understandable that the system provided in this embodiment further includes a high-speed interface module and a power module, wherein the high-speed interface module is used to implement data transmission between modules, and the power module is used to supply power to the entire system.

[0155] The system provided in this embodiment can be used to implement the method proposed in the first aspect above. Since it is basically similar to the method embodiment, the description is relatively simple. For relevant details, please refer to the partial description of the method embodiment. Therefore, the system also has the same or similar beneficial effects as the above method.

[0156] The beneficial effects of the present invention are verified and explained through simulation experiments below.

[0157] 1. Experimental conditions

[0158] This experiment focuses on SAR jamming technology. The DDR (MT40A512M16L) module is used to store and read the DAC output signal. Data analysis is performed in MATLAB to verify the correctness of the intermediate frequency interference signal generated by the FPGA signal processing board. Finally, the data after two-dimensional sinusoidal frequency modulation regional controllable interference is imaged on the spaceborne SAR to verify the correctness and engineering practicality of the invention.

[0159] The experimental parameters are: spaceborne SAR carrier frequency , intermediate frequency carrier frequency , pulse width ,bandwidth , initial center slope distance 、SAR platform flight speed .

[0160] 2. Experimental content and results analysis

[0161] See Figure 9-10 , Figure 9 This is the MATLAB frequency domain diagram of the DAC output data when the range interference modulation coefficient is 4 in the simulation experiment; , forwarding interference signal spectrum times, the theoretical number of false targets generated is As you can see, Figure 9 There are 11 frequency components in it, which is consistent with the theoretical number of frequency components.

[0162] Figure 10 This is the MATLAB frequency domain diagram of the DAC output data when the range interference modulation coefficient is 100 in the simulation experiment; , forwarding interference signal spectrum times, the theoretical number of false targets generated is ,observe Figure 11 The number of frequency components is large and densely distributed, which is basically consistent with the theoretical expectation of the number of frequency components.

[0163] See Figure 11 , Figure 11 This is the imaging result of the original data of spaceborne SAR in the simulation experiment. The data after the spaceborne SAR is subjected to two-dimensional sinusoidal frequency modulation regional controllable interference is imaged. The results are as follows Figure 12-15 As shown, Figure 12 This is the imaging result after implementing two-dimensional sinusoidal frequency modulation regional controllable interference in the simulation experiment when the range interference modulation coefficient is 100, the range interference range is 1km, the azimuth interference modulation coefficient is 100, and the azimuth interference range is 1km; Figure 13 This is the imaging result after implementing two-dimensional sinusoidal frequency modulation regional controllable interference in the simulation experiment when the range interference modulation coefficient is 4, the range interference range is 1km, the azimuth interference modulation coefficient is 2, and the azimuth interference range is 1km; Figure 14 This is the imaging result after implementing two-dimensional sinusoidal frequency modulation regional controllable interference in the simulation experiment when the range interference modulation coefficient is 100, the range interference range is 5km, the azimuth interference modulation coefficient is 100, and the azimuth interference range is 10km; Figure 15 This is the imaging result after implementing two-dimensional sinusoidal frequency modulation regional controllable interference in the simulation experiment when the range interference modulation coefficient is 4, the range interference range is 5km, the azimuth interference modulation coefficient is 2, and the azimuth interference range is 10km.

[0164] The interference ranges in the range and azimuth directions controlled by this experiment are and ,according to Figure 14 and Figure 15 The imaging results show that the present invention achieves accurate control of the interference range. This experiment controls the interference modulation coefficient to be the same as the control interference range. and According to the imaging results, the present invention not only realizes accurate control of the interference range, but also realizes accurate control of the interference intensity within the determined interference range.

[0165] The above is a further detailed description of the present invention in conjunction with specific preferred embodiments, and the specific implementation of the present invention should not be considered to be limited to these descriptions. For those skilled in the art of the present invention, without departing from the concept of the present invention, several simple deductions or substitutions can be made, which should be considered to fall within the scope of protection of the present invention.

Claims

1. A two-dimensional sinusoidal frequency modulation regional controllable SAR interference implementation method, characterized in that: include: Step 1: Down-convert the received radar signal to obtain an intermediate frequency signal; Step 2: Input the intermediate frequency signal into the FPGA and perform the following processing: Performing ADC sampling on the intermediate frequency signal to obtain multiple digital signals; Calculation is performed based on the multi-channel digital signals and preset interference parameters, and the DDS IP core is used to generate interference in the range and azimuth directions, thereby generating a two-dimensional sinusoidal frequency modulation forwarding interference signal; Converting the two-dimensional sinusoidal frequency modulation forwarding interference signal into an analog signal; Step 3: After up-converting the analog signal, the analog signal is sent out through a transmitting antenna so that a two-dimensional interference signal is formed when the SAR receives the echo and performs coherent accumulation; Wherein, in step 2, calculation is performed based on the multi-channel digital signals and preset interference parameters, and the DDSIP core is used to generate interference in the range and azimuth directions, thereby generating a two-dimensional sinusoidal frequency modulation forwarding interference signal, including: Conducting reconnaissance on the multiple digital signals to obtain effective radar pulse signals; Based on the radar pulse effective signal and the preset range interference parameters, a range interference signal is generated using the DDS IP core; Based on the radar pulse effective signal and the preset azimuth interference parameters, the DDS IP core is used to generate an azimuth interference signal; The distance interference signal, the azimuth interference signal and the multi-channel digital signal are multiplied to generate a two-dimensional sinusoidal frequency modulation forwarding interference signal.

2. A two-dimensional sinusoidal frequency modulation regional controllable SAR interference implementation method according to claim 1, characterized in that: Based on the radar pulse effective signal and the preset range interference parameters, the DDS IP core is used to generate a range interference signal, including: According to the preset range interference range and range interference modulation coefficient, the FPGA internal divider IP core and multiplier IP core are used to calculate the interval between adjacent false targets and the range modulation frequency. Calculating a range frequency control word according to the range modulation frequency and the range interference modulation coefficient; The range frequency control word is input into a multi-channel parallel DDS IP core to generate a multi-channel parallel range interference signal.

3. A two-dimensional sinusoidal frequency modulation regional controllable SAR interference implementation method according to claim 2, characterized in that: The calculation formulas for the interval between adjacent false targets in the range direction and the modulation frequency in the range direction are: ； In the formula, Indicates the distance to adjacent false targets; Indicates the interference range in distance direction; represents the interference modulation coefficient in the range direction; represents the range modulation frequency; represents the range modulation frequency, which is obtained by dividing the bandwidth of the effective radar pulse signal by the pulse width; Represents the speed of light.

4. A two-dimensional sinusoidal frequency modulation regional controllable SAR interference implementation method according to claim 3, characterized in that: The calculation formula of the distance frequency control word is: ； In the formula, Indicates the range frequency control word; Indicates distance to fast time; Indicates the distance frequency control word width of the multi-channel parallel DDS IP core; Indicates the working clock of the DDS IP core.

5. A two-dimensional sinusoidal frequency modulation regional controllable SAR interference implementation method according to claim 4, characterized in that: The multi-path parallel range interference signal is expressed as: ； In the formula, Indicates channel The distance interference signal generated is Indicates the channel number; Indicates the total number of channels.

6. A two-dimensional sinusoidal frequency modulation regional controllable SAR interference implementation method according to claim 1, characterized in that: Based on the radar pulse effective signal and the preset azimuth interference parameters, the DDS IP core is used to generate an azimuth interference signal, including: According to the preset azimuth interference range and azimuth interference modulation coefficient, the azimuth modulation frequency of the interval between adjacent false targets in azimuth is calculated using the internal FPGA divider IP core and multiplier IP core. Calculate the azimuth frequency control word according to the azimuth modulation frequency, the flight speed of the SAR platform and the center slant range; The azimuth frequency control word is input into a single DDS IP core to generate one azimuth interference signal, and the one azimuth interference signal is copied into multiple parallel signals to obtain multiple parallel azimuth interference signals.

7. A two-dimensional sinusoidal frequency modulation regional controllable SAR interference implementation method according to claim 6, characterized in that: The calculation formula of the adjacent false target interval in the azimuth direction and the modulation frequency in the azimuth direction is: ； In the formula, Indicates the interval between adjacent false targets in azimuth; Indicates the interference range in azimuth; Indicates the interference modulation coefficient in azimuth; Indicates the azimuth modulation frequency; Indicates the flight speed of the SAR platform; Indicates the carrier wavelength; Indicates the center slope distance.

8. A two-dimensional sinusoidal frequency modulation regional controllable SAR interference implementation method according to claim 7, characterized in that: The calculation formula of the azimuth frequency control word is: ； In the formula, Indicates the azimuth frequency control word; Indicates azimuth slow time; Indicates the azimuth frequency control word width of the DDS IP core; Indicates the working clock of the DDS IP core.

9. A two-dimensional sinusoidal frequency modulation regional controllable SAR interference implementation system, used to implement the method described in any one of claims 1 to 8, characterized in that: The system includes a receiving antenna, a microwave board, an ADC signal acquisition module, an FPGA digital signal processing board, a host computer, a DAC digital-to-analog conversion module and a transmitting antenna; The receiving antenna is used to receive radar signals; The microwave board is used to perform down-conversion processing on the received radar signal to obtain an intermediate frequency signal; The ADC signal acquisition module is used to perform ADC sampling on the intermediate frequency signal to obtain multiple digital signals; The FPGA digital signal processing board is used to perform calculations based on the multi-channel digital signals and preset interference parameters, and use the DDS IP core to generate interference in the range and azimuth directions, thereby generating a two-dimensional sinusoidal frequency modulation forwarding interference signal; The host computer is used to provide preset interference parameters to the FPGA digital signal processing board; The DAC digital-to-analog conversion module is used to convert the two-dimensional sinusoidal frequency modulation forwarding interference signal into an analog signal; The microwave board is also used to perform up-conversion processing on the analog signal; The transmitting antenna is used to transmit the signal after the frequency conversion processing, so that the SAR receives the echo and performs coherent accumulation to form a two-dimensional interference signal.

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