SAR two-dimensional interference method and device based on four-phase coding period modulation

Abstract

The invention discloses an SAR two-dimensional interference method and device based on four-phase coding period modulation, and belongs to the technical field of radar countermeasure. According to the method, by combining distance direction frequency shift modulation, distance direction four-phase coding period modulation, azimuth direction frequency shift modulation and azimuth direction four-phase coding period modulation, 196 different types of two-dimensional interference effects, including symmetrically and asymmetrically distributed false targets, can be flexibly generated. According to the method, a unified modulation theory model is adopted, the generation process of the interference signal is simplified, the operation complexity is reduced, meanwhile, the center position of the interference result can be accurately controlled, and the two-dimensional interference effect of different types with the symmetrical distribution state and the asymmetrical distribution state of false targets of all orders is flexibly achieved.

Description

Technical Field

[0001] This invention belongs to the field of radar countermeasures technology, specifically relating to a SAR two-dimensional jamming method and apparatus based on four-phase coded periodic modulation. Background Technology

[0002] Synthetic Aperture Radar (SAR) is an active microwave imaging radar system characterized by all-weather, all-day, long-range, and high-resolution imaging capabilities. It is widely used in resource exploration, environmental monitoring, land surveying, and military reconnaissance. With the rapid development of SAR technology, its imaging capabilities are constantly improving, which also places higher demands on radar countermeasures. Traditional SAR jamming methods are mainly divided into two categories: suppression jamming and deception jamming.

[0003] Suppression jamming attempts to overwhelm or obscure the true echo signal of a target area by transmitting high-power incoherent noise signals. However, since suppression jamming is difficult to achieve with the processing gain of a SAR system, the jammer needs to have extremely high transmit power, which poses a significant challenge in engineering implementation.

[0004] Deception jamming generates false target or scene interference signals by accurately estimating the parameters and modulating the intercepted SAR signals in multiple dimensions. Deception jamming has advantages such as rich patterns, flexible control, and low power requirements, but its system design is complex and it has extremely high requirements for parameter detection accuracy and real-time processing, making it difficult to implement in engineering.

[0005] In deception and jamming techniques, phase-coded modulation (PCM) is an important jamming method. In existing technologies, researchers (Chinese Patent Publication No. CN118348531A) have proposed a SAR image modulation method based on periodic cyclic phase coding. This method modulates SAR signals intra-pulse using phase-coded sequences to generate range-direction point-array jamming effects. However, this method only achieves one-dimensional jamming effects, with limited jamming patterns, making it difficult to meet the needs of complex scenarios. Other researchers (Chinese Patent Publication No. CN119414345A) have proposed a jamming signal generation method based on azimuth-direction sinusoidal function quadratic modulation and range-direction phase-coded modulation. By combining multiple modulation methods, this method achieves six different types of two-dimensional jamming effects and can precisely control the center position of the jamming result. However, this method relies on two different phase-coded sequences and complex sinusoidal function quadratic modulation, resulting in high computational complexity and implementation difficulty, which is not conducive to engineering applications. Another researcher (Chinese Patent Publication No. CN119575320B) proposed a method for generating secondary modulation interference signals. By simultaneously employing secondary modulation techniques combining sinusoidal function modulation and periodic phase-coded modulation in both the range and azimuth directions, nine different types of two-dimensional interference effects were achieved, and the center position of the interference result could be precisely controlled. However, this method requires secondary modulation processing in both the range and azimuth directions. Although the interference effect is improved, the computational load of the algorithm is further increased, making implementation more difficult.

[0006] In summary, existing phase-coded modulation jamming methods suffer from problems such as limited jamming patterns, high algorithm complexity, and difficulty in engineering implementation. Therefore, there is an urgent need for a SAR two-dimensional jamming method that offers rich jamming patterns, flexible control, and ease of implementation to meet the requirements of modern radar countermeasures. Summary of the Invention

[0007] To address the aforementioned technical problems, this invention provides a SAR two-dimensional jamming method and apparatus based on four-phase coded periodic modulation. It combines range-direction frequency shift modulation, range-direction four-phase coded periodic modulation, azimuth-direction frequency shift modulation, and azimuth-direction four-phase coded periodic modulation, which can flexibly generate various types of two-dimensional jamming effects that combine symmetrical and asymmetrical distributions of false targets of various orders, while also being able to precisely control the center position of the jamming result.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] On one hand, the present invention provides a SAR two-dimensional jamming method based on four-phase coded periodic modulation, the method comprising:

[0010] Step 1: The jammer detects and receives the signals transmitted by the target SAR system, and obtains the digital SAR signal after down-conversion and analog-to-digital conversion. The digital SAR signal is then measured and stored.

[0011] Step 2: Set the period and phase symbols of the range-direction four-phase coded periodic modulation signal according to the interference requirements and digital SAR signal parameters, and generate the range-direction frequency shift modulation signal based on the range offset;

[0012] Step 3: Set the period and phase symbols of the azimuth four-phase coded periodic modulation signal according to the interference requirements and digital SAR signal parameters, and generate the azimuth frequency shift modulation signal based on the azimuth offset.

[0013] Step 4: Based on the range-direction four-phase coded periodic modulation signal, the range-direction frequency shift modulation signal, and the digital SAR signal, range-direction modulation is completed in the fast time domain to obtain the range-direction modulated SAR signal. Based on the azimuth-direction four-phase coded periodic modulation signal, the azimuth-direction frequency shift modulation signal, and the range-direction modulated SAR signal, azimuth-direction modulation is completed in the slow time domain to obtain the required digital jamming signal.

[0014] Step 5: After digital-to-analog conversion and up-conversion processing, the digital jamming signal is forwarded to the target SAR system so that it produces different types of two-dimensional jamming effects after imaging processing.

[0015] On the other hand, the present invention provides a SAR two-dimensional jamming device based on four-phase coded periodic modulation, comprising:

[0016] The receiving module is used to detect and receive signals transmitted by the target SAR system using a jammer, and obtain digital SAR signals after down-conversion and analog-to-digital conversion. The digital SAR signals are then measured and stored.

[0017] The range modulation module is used to set the period and phase symbols of the range four-phase coded periodic modulation signal according to the interference requirements and digital SAR signal parameters, and to generate the range frequency shift modulation signal based on the range offset.

[0018] The azimuth modulation module is used to set the period and phase symbols of the azimuth four-phase coded periodic modulation signal according to the interference requirements and digital SAR signal parameters, and to generate the azimuth frequency shift modulation signal based on the azimuth offset.

[0019] The jamming module is used to obtain a range-modulated SAR signal by performing range modulation in the fast time domain based on a range-direction four-phase coded periodic modulation signal, a range-direction frequency-shift modulation signal, and a digital SAR signal, and to obtain the required digital jamming signal by performing azimuth modulation in the slow time domain based on a azimuth-direction four-phase coded periodic modulation signal, a azimuth-direction frequency-shift modulation signal, and a range-direction modulated SAR signal.

[0020] The output module is used to forward digital jamming signals to the target SAR system after digital-to-analog conversion and up-conversion, so that different types of two-dimensional jamming effects are generated after imaging processing.

[0021] Thirdly, the present invention provides an electronic device, comprising: one or more processors; and a memory for storing one or more programs; wherein, when the one or more programs are executed by the one or more processors, the one or more processors implement the aforementioned SAR two-dimensional jamming method based on four-phase coded periodic modulation.

[0022] Fourthly, the present invention provides a computer-readable storage medium having executable instructions stored thereon, which, when executed by a processor, enable the processor to implement the aforementioned SAR two-dimensional jamming method based on four-phase coded periodic modulation.

[0023] The beneficial effects of this invention are as follows:

[0024] First, this invention achieves diversified and flexible control of interference patterns by combining range-direction frequency-shift modulation, range-direction four-phase coded periodic modulation, azimuth-direction frequency-shift modulation, and azimuth-direction four-phase coded periodic modulation. This method can generate 14 different interference patterns in both the range and azimuth directions, and through combinations, can form 196 two-dimensional interference effects with varying positions or energy distributions. This rich variety of interference patterns can effectively cope with complex and ever-changing SAR imaging scenarios, significantly improving the adaptability and effectiveness of the interference.

[0025] Secondly, this invention employs a unified four-phase coded periodic modulation theoretical model, simplifying the interference signal generation process. Compared with existing technologies, this method only requires one modulation method for modulation, eliminating the need for combinations of multiple different modulation methods or complex secondary modulation techniques, significantly reducing the computational load and implementation difficulty of the algorithm. This not only improves the efficiency of interference signal generation but also enhances the engineering feasibility of the system, providing convenience for practical applications.

[0026] Furthermore, this invention can precisely control the center position of the jamming result. By adjusting the frequency shifts in the range and azimuth directions, the jamming effect can be flexibly positioned at any location within the target area. This precise position control capability makes the jamming more targeted and covert, better meeting tactical requirements. Simultaneously, the jamming effect produced by this method exhibits both symmetrical and asymmetrical distributions of false targets at various orders, further enhancing the deceptiveness and misleading nature of the jamming.

[0027] Finally, this invention significantly reduces system complexity while maintaining diverse jamming effects. By optimizing modulation techniques and theoretical models, this method achieves high-performance jamming while reducing dependence on hardware resources and improving system reliability and stability. This makes this invention suitable not only for high-end military applications but also for playing an important role in the civilian sector, demonstrating broad application prospects. Attached Figure Description

[0028] Figure 1 This is a flowchart of the SAR two-dimensional jamming method based on four-phase coded periodic modulation of the present invention;

[0029] Figure 2 This is a typical SAR interference scenario diagram;

[0030] Figure 3 This is a time-domain waveform diagram of a range-oriented four-phase coded periodic modulation sequence;

[0031] Figure 4 This is a time-domain waveform diagram of a four-phase coded periodic modulation sequence in the azimuth direction;

[0032] Figure 5 These are the simulation results of the echo signal when the jammer is not working, where (a) is a two-dimensional amplitude diagram, (b) is a range slice diagram of the jamming center position, and (c) is an azimuth slice diagram of the jamming center position.

[0033] Figure 6 The interference pattern AA effect diagram is generated based on the method of the present invention, wherein (a) is a two-dimensional amplitude diagram, (b) is a distance slice diagram of the interference center position, and (c) is an azimuth slice diagram of the interference center position.

[0034] Figure 7 The image shows the interference pattern BB effect generated by the method of this invention, where (a) is a two-dimensional amplitude diagram, (b) is a distance slice diagram of the interference center position, and (c) is an azimuth slice diagram of the interference center position.

[0035] Figure 8 The image shows the interference pattern CC effect diagram generated by the method of this invention, where (a) is a two-dimensional amplitude diagram, (b) is a distance slice diagram of the interference center position, and (c) is an azimuth slice diagram of the interference center position.

[0036] Figure 9 The diagram shows the interference pattern DD effect generated by the method of this invention, where (a) is a two-dimensional amplitude diagram, (b) is a distance slice diagram of the interference center position, and (c) is an azimuth slice diagram of the interference center position.

[0037] Figure 10The diagram shows the interference pattern EE effect generated by the method of this invention, where (a) is a two-dimensional amplitude diagram, (b) is a distance slice diagram of the interference center position, and (c) is an azimuth slice diagram of the interference center position.

[0038] Figure 11 The image shows the interference pattern FF effect generated by the method of the present invention, where (a) is a two-dimensional amplitude image, (b) is a distance slice image of the interference center position, and (c) is an azimuth slice image of the interference center position.

[0039] Figure 12 The image shows the interference pattern GG effect generated by the method of this invention, where (a) is a two-dimensional amplitude image, (b) is a distance slice image of the interference center position, and (c) is an azimuth slice image of the interference center position.

[0040] Figure 13 The above is an interference pattern HH effect diagram generated based on the method of the present invention, wherein (a) is a two-dimensional amplitude diagram, (b) is a distance slice diagram of the interference center position, and (c) is an azimuth slice diagram of the interference center position.

[0041] Figure 14 The diagram shows the effect of interference pattern II generated by the method of the present invention, where (a) is a two-dimensional amplitude diagram, (b) is a distance slice diagram of the interference center position, and (c) is an azimuth slice diagram of the interference center position.

[0042] Figure 15 The diagram shows the effect of the interference pattern JJ generated by the method of the present invention, wherein (a) is a two-dimensional amplitude diagram, (b) is a distance slice diagram of the interference center position, and (c) is an azimuth slice diagram of the interference center position.

[0043] Figure 16 The diagram shows the interference pattern KK effect generated by the method of this invention, where (a) is a two-dimensional amplitude diagram, (b) is a distance slice diagram of the interference center position, and (c) is an azimuth slice diagram of the interference center position.

[0044] Figure 17 The diagram shows the interference pattern LL effect generated by the method of this invention, where (a) is a two-dimensional amplitude diagram, (b) is a distance slice diagram of the interference center position, and (c) is an azimuth slice diagram of the interference center position.

[0045] Figure 18 The image shows the interference pattern MM effect generated by the method of this invention, where (a) is a two-dimensional amplitude diagram, (b) is a distance slice of the interference center position, and (c) is an azimuth slice of the interference center position.

[0046] Figure 19The diagram shows the interference pattern NN effect generated by the method of this invention, where (a) is a two-dimensional amplitude diagram, (b) is a distance slice diagram of the interference center position, and (c) is an azimuth slice diagram of the interference center position.

[0047] Figure 20 Center position control example based on the method of this invention Figure 1 ;

[0048] Figure 21 Center position control example based on the method of this invention Figure 2 ;

[0049] Figure 22 Center position control example based on the method of this invention Figure 3 ;

[0050] Figure 23 Center position control example based on the method of this invention Figure 4 ;

[0051] Figure 24 This is an example diagram of the framework of the SAR two-dimensional jamming device based on four-phase coding periodic modulation according to the present invention. Detailed Implementation

[0052] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0053] The purpose of this invention is to provide a SAR two-dimensional jamming method and apparatus that combines range-direction frequency shift modulation, range-direction four-phase coded periodic modulation, azimuth-direction frequency shift modulation, and azimuth-direction four-phase coded periodic modulation. This method can flexibly achieve two-dimensional jamming effects for different types of false targets with symmetrical and asymmetrical distributions of various orders, while also accurately controlling the center position of the jamming result.

[0054] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0055] like Figure 1 As shown, this invention discloses a two-dimensional SAR jamming method based on four-phase coded periodic modulation, comprising the following steps:

[0056] Step 1: The jammer detects and receives the signal transmitted by the target SAR system. After down-conversion and analog-to-digital conversion, a digital SAR signal is obtained. The digital SAR signal is then measured and stored. The jammer first detects and receives the signal transmitted by the target SAR system. At the same time, it down-converts the intercepted SAR signal to obtain a baseband SAR signal. Then, it uses an analog-to-digital converter to sample the analog SAR signal to obtain a digital SAR signal. Subsequently, it measures signal parameters including bandwidth, pulse width, frequency modulation slope, and pulse repetition period and stores the digital SAR signal.

[0057] Step 2: Set the period and phase symbols of the range-direction four-phase coded periodic modulation signal according to the interference requirements and digital SAR signal parameters, and generate the range-direction frequency shift modulation signal based on the range offset;

[0058] Step 3: Set the period and phase symbols of the azimuth four-phase coded periodic modulation signal according to the interference requirements and digital SAR signal parameters, and generate the azimuth frequency shift modulation signal based on the azimuth offset.

[0059] Step 4: Based on the range-direction four-phase coded periodic modulation signal, the range-direction frequency shift modulation signal, and the digital SAR signal, range-direction modulation is completed in the fast time domain to obtain the range-direction modulated SAR signal. Based on the azimuth-direction four-phase coded periodic modulation signal, the azimuth-direction frequency shift modulation signal, and the range-direction modulated SAR signal, azimuth-direction modulation is completed in the slow time domain to obtain the required digital jamming signal.

[0060] Step 5: The digital jamming signal is forwarded to the target SAR system after digital-to-analog conversion and up-conversion processing, so that it produces different types of two-dimensional jamming effects after imaging processing. The jammer converts the digital jamming signal into an analog jamming signal through a digital-to-analog converter, then performs up-conversion processing on the analog jamming signal and forwards it to the target SAR system pulse by pulse. The target SAR system performs down-conversion and analog-to-digital conversion processing on the analog jamming signal to obtain the baseband jamming signal. After imaging processing by the target SAR system, the baseband jamming signal can produce different types of jamming effects.

[0061] Typical SAR interference scenarios, such as Figure 2 As shown, the flight speed of the front-side looking airborne SAR platform is set to... Flight altitude is jammer Located at the center of the SAR system imaging mapping strait and with coordinates , with SAR flight direction as The axis, vertically upward direction is Establish a coordinate system along the axes. Set the initial slant range from the jammer to the SAR platform as follows: The instantaneous slant distance is Then the calculation yields , .

[0062] The specific implementation process of step one is as follows:

[0063] Transmitted signals of target SAR system The expression is as follows:

[0064] ,

[0065] in, For distance to time, The pulse duration, For carrier frequency, The frequency modulation slope of the linear frequency modulated signal. It is the imaginary unit.

[0066] The jammer down-converts and samples the intercepted SAR signal to obtain a digital SAR signal. The expression for the digital SAR signal is as follows:

[0067] ,

[0068] in, At the speed of light, Let P be the instantaneous slant range from the jammer to the SAR platform. For azimuth and time. Further, the captured SAR signal is stored, and parameters such as bandwidth, pulse width, frequency modulation slope, and pulse repetition period of the captured SAR signal are measured.

[0069] The specific implementation process of step two is as follows:

[0070] The values ​​of the range-direction phase modulation symbol sequence determine the range-direction interference pattern generated by the interference signal. Therefore, the range-direction phase modulation symbols are set according to the interference requirements. And the modulation phases corresponding to the modulation symbols are respectively , , and The period of the range-direction four-phase coded periodic modulation signal can adjust the range-direction spacing of adjacent false targets in the jamming result. Since the range-direction spacing of adjacent false targets in the jamming result is simultaneously affected by SAR signal parameters, the modulation phases are set to alternate and the duration is determined based on the jamming requirements and the measured signal parameters. This results in a period of The distance-oriented four-phase coded periodic modulated signal has the following time-domain waveform: Figure 3 As shown.

[0071] Using Fourier series theory, the range-oriented four-phase coded periodic phase modulated signal can be converted into the following form:

[0072] ,

[0073] in:

[0074] ,

[0075] This indicates the harmonic order of the range-oriented four-phase coded periodic phase modulated signal. Represents the angular frequency of the range-oriented four-phase coded periodic modulated signal and Furthermore, the range-direction frequency shift is set according to the required range-direction offset. And it generates a range-direction frequency-shift modulated signal, the expression of which is: .

[0076] The specific implementation process of step three is as follows:

[0077] The values ​​of the azimuth phase modulation symbol sequence determine the azimuth interference pattern generated by the interference signal. Therefore, the azimuth phase modulation symbols are set according to the interference requirements. And the modulation phases corresponding to the modulation symbols are respectively , , and The period of the azimuth four-phase coded periodic modulation signal can adjust the azimuth spacing of adjacent false targets in the jamming result. Since the azimuth spacing of adjacent false targets in the jamming result is also affected by SAR signal parameters, the modulation phases are set to alternate and the duration is determined according to the jamming requirements and the measured signal parameters. This results in a period of The azimuth-oriented four-phase coded periodic modulated signal has the following time-domain waveform: Figure 4 As shown.

[0078] Using Fourier series theory, the azimuth-oriented four-phase coded periodic phase-modulated signal can be converted into the following form:

[0079] ,

[0080] in:

[0081] ,

[0082] This indicates the harmonic order of the azimuth-oriented four-phase coded periodic phase modulated signal. The angular frequency of the azimuth-oriented four-phase coded periodic modulated signal is represented by... In addition, the azimuth frequency shift amount is set according to the required azimuth offset. And it generates an azimuth frequency shift modulation signal, the expression of which is: .

[0083] The specific implementation process of step four is as follows:

[0084] The jammer first multiplies the range-direction frequency-shift modulation signal and the range-direction four-phase-coded periodic modulation signal sequentially with the digital SAR signal, sampling point by sampling point, to complete range-direction modulation and obtain the range-direction modulated SAR signal. Then, based on the azimuth time corresponding to the range-direction modulated SAR signal, it multiplies the sampling points corresponding to the azimuth-direction frequency-shift modulation signal and the azimuth-direction four-phase-coded periodic modulation signal with all sampling points of the range-direction modulated SAR signal, thus completing azimuth modulation. After the above processing, the jammer finally generates the desired digital jamming signal, the expression of which is shown below:

[0085] ,

[0086] The specific implementation process of step five is as follows:

[0087] The jammer converts the digital jamming signal into an analog jamming signal using a digital-to-analog converter (DAC). It then up-converts the analog jamming signal and forwards the up-converted signal pulse-by-pulse to the target SAR system. Analysis shows that the expression for the jamming signal after down-conversion and analog-to-digital conversion by the target SAR system is:

[0088] ,

[0089] The imaging characteristics of the interference model are analyzed using the Range-Doppler Algorithm (RD algorithm, a classic algorithm in synthetic aperture radar (SAR) imaging processing, mainly used to convert radar echo signals into two-dimensional high-resolution images). First, a range-frequency domain matched filter is used. The interference signal is subjected to range-direction pulse compression processing, where The range frequency is then represented, followed by the use of an azimuth frequency domain matched filter. ,in Indicates the azimuth frequency. Azimuth pulse compression processing is performed on the interference signal, and the final imaging result is:

[0090] ,

[0091] in, The pulse duration, For the time to synthesize the pore size, For azimuth frequency modulation and Based on the above results, it can be seen that the range direction is shifted after frequency shift modulation, and further shifted after four-phase coding periodic modulation will generate multiple frequency shift modulations on the basis of the position shift, producing false targets of various orders.

[0092] Among them, distance direction The location of the second-order false target is:

[0093] ,

[0094] Distance The magnitude of the order of false targets is:

[0095] ,

[0096] Based on the above results, it can be seen that the azimuth direction is shifted after frequency shift modulation. After further azimuth direction four-phase coding periodic modulation, multiple frequency shift modulations will be formed on the basis of the position shift, generating false targets of various orders.

[0097] Among them, directional The location of the second-order false target is:

[0098] ,

[0099] Orientation The magnitude of the order of false targets is:

[0100] ,

[0101] The theoretical model of this invention is verified and analyzed below based on simulation results. First, the spectral characteristics of four-phase coded periodic modulated signals with different modulation symbols are verified using the Fourier coefficient expression. The table below shows the numerical simulation results of the spectrum of the four-phase coded periodic modulated signals corresponding to different symbol combinations and the Fourier coefficient expression. The results show that the theoretical analysis and simulation results are consistent.

[0102]

[0103]

[0104]

[0105]

[0106] Based on the above results, it can be seen that when the symbol sequences are 0000, 1111, 2222, and 3333, the spectral characteristics of the four-phase coded periodic modulation signal are the same as those of a DC signal. Therefore, the four-phase coded periodic modulation signal corresponding to the above symbols cannot produce an effective interference modulation effect. In summary, by changing the symbol sequence, the four-phase coded periodic modulation signal can generate 14 different types of spectral patterns with both symmetrical and asymmetrical distributions of harmonics of various orders. The interference model proposed in this invention uses the four-phase coded periodic modulation signal to perform product modulation on the target SAR signal. Its modulation effect is equivalent to shifting and copying the spectrum of the target SAR signal according to the spectral pattern of the four-phase coded periodic modulation signal. Therefore, the interference model proposed in this invention can achieve 14 different types of effective interference patterns with both symmetrical and asymmetrical distributions of false targets of various orders in both the range and azimuth directions. For ease of distinction, the letters A to N are used to represent the different types of effective interference patterns generated by the interference model.

[0107] Based on the interference model, it can be seen that the jammer applies range-direction four-phase coded periodic modulation, range-direction frequency-shift modulation, azimuth-direction four-phase coded periodic modulation, and azimuth-direction frequency-shift modulation to the intercepted SAR signal to obtain the desired interference signal. Therefore, by changing the symbol sequence, range-direction four-phase coded periodic modulation can produce 14 different types of range-direction interference effects with both symmetrical and asymmetrical distributions of false targets of various orders, and azimuth-direction four-phase coded periodic modulation can produce 14 different types of azimuth-direction interference effects with both symmetrical and asymmetrical distributions of false targets of various orders. In summary, the interference signal generated by this interference model can produce 196 different types of two-dimensional interference effects with both symmetrical and asymmetrical distributions of false targets of various orders.

[0108] Furthermore, to verify the effectiveness of the interference model, simulations were performed on different types of interference patterns. Additionally, for ease of differentiation, interference pattern AB was defined as A representing the range-direction interference pattern and B representing the azimuth-direction interference pattern; similarly, other interference patterns were represented.

[0109] Set goals The system operates in strip imaging mode, with a working frequency band of [frequency band missing]. band, center frequency is The speed of the carrier aircraft is The signal bandwidth is The signal bandwidth is The pulse repetition frequency is According to simulation parameters, it can be calculated that... System range resolution for Azimuth resolution for The jammer is deployed at the zero point of the coordinate system. Figure 5 The image shows the simulation results of the echo signal when the jammer is not working. The jammer imaging result is a point target located at the zero point of the coordinate system. Among them, (a) is a two-dimensional amplitude map, (b) is a range slice map of the jamming center position, and (c) is a azimuth slice map of the jamming center position.

[0110] Set the range-direction frequency shift to The azimuth frequency shift is The code elements of the range-oriented four-phase coded periodic modulation signal are And the period is The symbols of the azimuth four-phase coded periodic modulation signal are And the period is According to theoretical model calculations and analysis, the interference pattern is AA and the center position of the interference result is... The simulation results are as follows: Figure 6 As shown, (a) is a two-dimensional amplitude diagram, (b) is a distance slice of the interference center location, and (c) is an azimuth slice of the interference center location, which is consistent with the theoretical analysis.

[0111] Set the range-direction frequency shift to The azimuth frequency shift is The code elements of the range-oriented four-phase coded periodic modulation signal are And the period is The symbols of the azimuth four-phase coded periodic modulation signal are And the period is According to theoretical model calculations and analysis, the interference pattern is BB and the center position of the interference result is... The simulation results are as follows: Figure 7 As shown, (a) is a two-dimensional amplitude diagram, (b) is a distance slice of the interference center location, and (c) is an azimuth slice of the interference center location, which is consistent with the theoretical analysis.

[0112] Set the range-direction frequency shift to The azimuth frequency shift is The code elements of the range-oriented four-phase coded periodic modulation signal are And the period is The symbols of the azimuth four-phase coded periodic modulation signal are And the period is According to theoretical model calculations and analysis, the interference pattern is CC and the center position of the interference result is... The simulation results are as follows: Figure 8 As shown, (a) is a two-dimensional amplitude diagram, (b) is a distance slice of the interference center location, and (c) is an azimuth slice of the interference center location, which is consistent with the theoretical analysis.

[0113] Set the range-direction frequency shift to The azimuth frequency shift is The code elements of the range-oriented four-phase coded periodic modulation signal are And the period is The symbols of the azimuth four-phase coded periodic modulation signal are And the period is According to theoretical model calculations and analysis, the interference pattern is DD and the center position of the interference result is... The simulation results are as follows: Figure 9 As shown, (a) is a two-dimensional amplitude diagram, (b) is a distance slice of the interference center location, and (c) is an azimuth slice of the interference center location, which is consistent with the theoretical analysis.

[0114] Set the range-direction frequency shift to The azimuth frequency shift is The code elements of the range-oriented four-phase coded periodic modulation signal are And the period is The symbols of the azimuth four-phase coded periodic modulation signal are And the period is According to theoretical model calculations and analysis, the interference pattern is EE and the center position of the interference result is... The simulation results are as follows: Figure 10 As shown, (a) is a two-dimensional amplitude diagram, (b) is a distance slice of the interference center location, and (c) is an azimuth slice of the interference center location, which is consistent with the theoretical analysis.

[0115] Set the range-direction frequency shift to The azimuth frequency shift is The code elements of the range-oriented four-phase coded periodic modulation signal are And the period is The symbols of the azimuth four-phase coded periodic modulation signal are And the period is According to theoretical model calculations and analysis, the interference pattern is FF and the center position of the interference result is... The simulation results are as follows: Figure 11 As shown, (a) is a two-dimensional amplitude diagram, (b) is a distance slice of the interference center location, and (c) is an azimuth slice of the interference center location, which is consistent with the theoretical analysis.

[0116] Set the range-direction frequency shift to The azimuth frequency shift is The code elements of the range-oriented four-phase coded periodic modulation signal are And the period is The symbols of the azimuth four-phase coded periodic modulation signal are And the period is According to theoretical model calculations and analysis, the interference pattern is GG and the center of the interference result is located at [location missing]. The simulation results are as follows: Figure 12 As shown, (a) is a two-dimensional amplitude diagram, (b) is a distance slice of the interference center location, and (c) is an azimuth slice of the interference center location, which is consistent with the theoretical analysis.

[0117] Set the range-direction frequency shift to The azimuth frequency shift is The code elements of the range-oriented four-phase coded periodic modulation signal are And the period is The symbols of the azimuth four-phase coded periodic modulation signal are And the period is According to theoretical model calculations and analysis, the interference pattern is HH and the center position of the interference result is... The simulation results are as follows: Figure 13 As shown, (a) is a two-dimensional amplitude diagram, (b) is a distance slice of the interference center location, and (c) is an azimuth slice of the interference center location, which is consistent with the theoretical analysis.

[0118] Set the range-direction frequency shift to The azimuth frequency shift is The code elements of the range-oriented four-phase coded periodic modulation signal are And the period is The symbols of the azimuth four-phase coded periodic modulation signal are And the period is According to theoretical model calculations and analysis, the interference pattern is II and the center position of the interference result is... The simulation results are as follows: Figure 14 As shown, (a) is a two-dimensional amplitude diagram, (b) is a distance slice of the interference center location, and (c) is an azimuth slice of the interference center location, which is consistent with the theoretical analysis.

[0119] Set the range-direction frequency shift to The azimuth frequency shift is The code elements of the range-oriented four-phase coded periodic modulation signal are And the period is The symbols of the azimuth four-phase coded periodic modulation signal are And the period is According to theoretical model calculations and analysis, the interference pattern is JJ and the center position of the interference result is... The simulation results are as follows: Figure 15As shown, (a) is a two-dimensional amplitude diagram, (b) is a distance slice of the interference center location, and (c) is an azimuth slice of the interference center location, which is consistent with the theoretical analysis.

[0120] Set the range-direction frequency shift to The azimuth frequency shift is The code elements of the range-oriented four-phase coded periodic modulation signal are And the period is The symbols of the azimuth four-phase coded periodic modulation signal are And the period is According to theoretical model calculations and analysis, the interference pattern is KK and the center position of the interference result is... The simulation results are as follows: Figure 16 As shown, (a) is a two-dimensional amplitude diagram, (b) is a distance slice of the interference center location, and (c) is an azimuth slice of the interference center location, which is consistent with the theoretical analysis.

[0121] Set the range-direction frequency shift to The azimuth frequency shift is The code elements of the range-oriented four-phase coded periodic modulation signal are And the period is The symbols of the azimuth four-phase coded periodic modulation signal are And the period is According to theoretical model calculations and analysis, the interference pattern is LL and the center position of the interference result is... The simulation results are as follows: Figure 17 As shown, (a) is a two-dimensional amplitude diagram, (b) is a distance slice of the interference center location, and (c) is an azimuth slice of the interference center location, which is consistent with the theoretical analysis.

[0122] Set the range-direction frequency shift to The azimuth frequency shift is The code elements of the range-oriented four-phase coded periodic modulation signal are And the period is The symbols of the azimuth four-phase coded periodic modulation signal are And the period is According to theoretical model calculations and analysis, the interference pattern is MM and the center position of the interference result is... The simulation results are as follows: Figure 18 As shown, (a) is a two-dimensional amplitude diagram, (b) is a distance slice of the interference center location, and (c) is an azimuth slice of the interference center location, which is consistent with the theoretical analysis.

[0123] Set the range-direction frequency shift to The azimuth frequency shift is The code elements of the range-oriented four-phase coded periodic modulation signal are And the period is The symbols of the azimuth four-phase coded periodic modulation signal are And the period is According to theoretical model calculations and analysis, the interference pattern is NN and the center position of the interference result is... The simulation results are as follows: Figure 19 As shown, (a) is a two-dimensional amplitude diagram, (b) is a distance slice of the interference center location, and (c) is an azimuth slice of the interference center location, which is consistent with the theoretical analysis.

[0124] Set the range-direction frequency shift to The azimuth frequency shift is The code elements of the range-oriented four-phase coded periodic modulation signal are And the period is The symbols of the azimuth four-phase coded periodic modulation signal are And the period is According to theoretical model calculations and analysis, the interference pattern is BB and the center position of the interference result is... The simulation results are as follows: Figure 20 As shown, this is consistent with the theoretical analysis.

[0125] Set the range-direction frequency shift to The azimuth frequency shift is The code elements of the range-oriented four-phase coded periodic modulation signal are And the period is The symbols of the azimuth four-phase coded periodic modulation signal are And the period is According to theoretical model calculations and analysis, the interference pattern is BB and the center position of the interference result is... The simulation results are as follows: Figure 21 As shown, this is consistent with the theoretical analysis.

[0126] Set the range-direction frequency shift to The azimuth frequency shift is The code elements of the range-oriented four-phase coded periodic modulation signal are And the period is The symbols of the azimuth four-phase coded periodic modulation signal are And the period is According to theoretical model calculations and analysis, the interference pattern is BB and the center position of the interference result is... The simulation results are as follows: Figure 22 As shown, this is consistent with the theoretical analysis.

[0127] Set the range-direction frequency shift to The azimuth frequency shift is The code elements of the range-oriented four-phase coded periodic modulation signal are And the period is The symbols of the azimuth four-phase coded periodic modulation signal are And the period is According to theoretical model calculations and analysis, the interference pattern is BB and the center position of the interference result is... The simulation results are as follows: Figure 23 As shown, this is consistent with the theoretical analysis.

[0128] Based on the simulation results above, it can be seen that by changing the symbol sequence of the four-phase coded periodic modulation signal, the novel SAR jamming method proposed in this invention achieves 14 different types of two-dimensional jamming effects with symmetrical and asymmetrical distributions of false targets of various orders in both the range and azimuth directions. Therefore, by combining the range-direction four-phase coded periodic modulation signal with the azimuth-direction four-phase coded periodic modulation signal corresponding to different symbol sequences, the novel SAR jamming method proposed in this invention can achieve 196 two-dimensional jamming effects with symmetrical and asymmetrical distributions of different positions or energy distributions, while accurately adjusting the center position of the jamming result, thus proving its effectiveness.

[0129] like Figure 24 As shown, the present invention provides a four-phase coded periodic modulation interference signal generation apparatus, the various modules of which can implement the various steps of the aforementioned method, specifically including:

[0130] The receiving module is used to detect and receive signals transmitted by the target SAR system using a jammer, and obtain digital SAR signals after down-conversion and analog-to-digital conversion. The digital SAR signals are then measured and stored.

[0131] The range modulation module is used to set the period and phase symbols of the range four-phase coded periodic modulation signal according to the interference requirements and digital SAR signal parameters, and to generate the range frequency shift modulation signal based on the range offset.

[0132] The azimuth modulation module is used to set the period and phase symbols of the azimuth four-phase coded periodic modulation signal according to the interference requirements and digital SAR signal parameters, and to generate the azimuth frequency shift modulation signal based on the azimuth offset.

[0133] The jamming module is used to obtain a range-modulated SAR signal by performing range modulation in the fast time domain based on a range-direction four-phase coded periodic modulation signal, a range-direction frequency-shift modulation signal, and a digital SAR signal, and to obtain the required digital jamming signal by performing azimuth modulation in the slow time domain based on a azimuth-direction four-phase coded periodic modulation signal, a azimuth-direction frequency-shift modulation signal, and a range-direction modulated SAR signal.

[0134] The output module is used to forward digital jamming signals to the target SAR system after digital-to-analog conversion and up-conversion, so that different types of two-dimensional jamming effects are generated after imaging processing.

[0135] Specifically, it includes: a signal reception module for receiving signals transmitted by the target SAR system; a down-conversion module for down-converting the intercepted SAR signals; an analog-to-digital conversion module for sampling the received target system SAR signals and converting them into digital signals; a signal parameter measurement module for measuring signal parameters such as pulse width, bandwidth, and pulse repetition frequency of the received intercepted SAR signals; a range-oriented four-phase-coded periodic modulation module for generating range-oriented four-phase-coded periodic modulation signals and performing intra-pulse modulation on the digital signals; a range-oriented frequency-shift modulation module for generating range-oriented frequency-shift modulation signals and performing intra-pulse modulation on the digital signals; an azimuth-oriented four-phase-coded periodic modulation module for generating azimuth-oriented four-phase-coded periodic modulation signals and performing inter-pulse modulation on the digital signals; an azimuth-oriented frequency-shift modulation module for generating azimuth-oriented frequency-shift modulation signals and performing inter-pulse modulation on the digital signals; a digital-to-analog conversion module for converting the modulated digital interference signals into analog interference signals; an up-conversion module for up-converting the analog baseband interference signals; and a transmission module for transmitting analog interference signals pulse by pulse.

[0136] The present invention provides an electronic device, comprising: one or more processors; and a memory for storing one or more programs; wherein, when the one or more programs are executed by the one or more processors, the one or more processors implement the aforementioned SAR two-dimensional jamming method based on four-phase coded periodic modulation.

[0137] The present invention provides a storage medium, which is a computer-readable storage medium capable of storing a computer program. When the program is executed by a processor, the device where the storage medium is located executes the method for generating a four-phase coded periodic modulation interference signal disclosed in the present invention.

[0138] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A SAR two-dimensional jamming method based on four-phase coded periodic modulation, characterized in that, The method includes: Step 1: The jammer detects and receives the signals transmitted by the target SAR system, and obtains the digital SAR signal after down-conversion and analog-to-digital conversion. The digital SAR signal is then measured and stored. Step 2: Set the period and phase symbols of the range-direction four-phase coded periodic modulation signal according to the interference requirements and digital SAR signal parameters, and generate the range-direction frequency shift modulation signal based on the range offset; Step 3: Set the period and phase symbols of the azimuth four-phase coded periodic modulation signal according to the interference requirements and digital SAR signal parameters, and generate the azimuth frequency shift modulation signal based on the azimuth offset. Step 4: Based on the range-direction four-phase coded periodic modulation signal, the range-direction frequency shift modulation signal, and the digital SAR signal, range-direction modulation is completed in the fast time domain to obtain the range-direction modulated SAR signal. Based on the azimuth-direction four-phase coded periodic modulation signal, the azimuth-direction frequency shift modulation signal, and the range-direction modulated SAR signal, azimuth-direction modulation is completed in the slow time domain to obtain the required digital jamming signal. Step 5: After digital-to-analog conversion and up-conversion processing, the digital jamming signal is forwarded to the target SAR system so that it produces different types of two-dimensional jamming effects after imaging processing.

2. The SAR two-dimensional jamming method based on four-phase coded periodic modulation according to claim 1, characterized in that, In step one, the target SAR system transmits signals. The expression is as follows: ， in, For distance to time, The pulse duration, For carrier frequency, The frequency modulation slope of the linear frequency modulated signal. The imaginary unit; The jammer down-converts and samples the intercepted SAR signal to obtain a digital SAR signal: ， in, At the speed of light, Let P be the instantaneous slant range from the jammer to the SAR platform. This refers to the direction of time.

3. The SAR two-dimensional jamming method based on four-phase coded periodic modulation according to claim 2, characterized in that, The measured digital SAR signal includes the measured bandwidth, pulse width, frequency modulation slope, and pulse repetition period parameters of the digital SAR signal.

4. The SAR two-dimensional jamming method based on four-phase coded periodic modulation according to claim 3, characterized in that, Step two includes: The range-direction interference pattern generated by the interference signal is determined by the values ​​of the range-direction phase modulation symbol sequence. Therefore, the range-direction phase modulation symbol is set according to the interference requirements. And the modulation phases corresponding to the modulation symbols are respectively , , and Set the modulation phase to alternate and the duration to be The generation cycle is The range-oriented four-phase coded periodic phase modulated signal can be converted into the following form using Fourier series theory: ， in: ， This indicates the harmonic order of the range-oriented four-phase coded periodic phase modulated signal. Represents the angular frequency of the range-oriented four-phase coded periodic modulated signal and Set the range shift amount according to the required range offset. And it generates a range-direction frequency-shift modulated signal, the expression of which is: .

5. The SAR two-dimensional jamming method based on four-phase coded periodic modulation according to claim 4, characterized in that, Step three includes: Considering that the values ​​of the azimuth phase modulation symbol sequence determine the azimuth interference pattern generated by the interference signal, the azimuth phase modulation symbol is set according to the interference requirements. And the modulation phases corresponding to the modulation symbols are respectively , , and Set the modulation phase to alternate and the duration to be The generation cycle is The azimuth four-phase coded periodic phase modulated signal can be converted into the following form using Fourier series theory: ， in: ， This indicates the harmonic order of the azimuth-oriented four-phase coded periodic phase modulated signal. The angular frequency of the azimuth-oriented four-phase coded periodic modulated signal is represented by... Set the azimuth frequency shift amount according to the required azimuth offset. And it generates an azimuth frequency shift modulation signal, the expression of which is: .

6. The SAR two-dimensional jamming method based on four-phase coded periodic modulation according to claim 5, characterized in that, Step four includes: The jammer first multiplies the range-direction frequency-shift modulation signal and the range-direction four-phase-coded periodic modulation signal with the digital SAR signal point by point to complete range-direction modulation and obtain the range-direction modulated SAR signal. Then, according to the azimuth time corresponding to the range-direction modulated SAR signal, the jammer multiplies the sampling points corresponding to the azimuth frequency-shift modulation signal and the azimuth four-phase-coded periodic modulation signal with all the sampling points of the range-direction modulated SAR signal to complete azimuth modulation and finally generate the required digital jamming signal.

7. The SAR two-dimensional jamming method based on four-phase coded periodic modulation according to claim 6, characterized in that, Step five includes: the jammer converts the digital jamming signal into an analog jamming signal using a digital-to-analog converter, then performs up-conversion processing on the analog jamming signal and forwards the up-converted jamming signal pulse by pulse to the target SAR system. The expression of the jamming signal after down-conversion and analog-to-digital conversion processing by the target SAR system is: ， The imaging characteristics of the interference model were analyzed using the range-Doppler RD algorithm. Range-direction frequency-domain matched filters were used to perform range-direction pulse compression on the interference signal, and azimuth-direction frequency-domain matched filters were used to perform azimuth-direction pulse compression on the interference signal. The final imaging result is as follows: ， in, The pulse duration, For the time to synthesize the pore size, For azimuth frequency modulation and ; After range-direction frequency shift modulation, a position offset is generated. Then, after range-direction four-phase coded periodic modulation, multiple frequency shift modulations are formed based on the position offset, generating false targets of various orders. Among these, the range-direction... The location of the second-order false target is: ， Distance The magnitude of the order of false targets is: ， After azimuth modulation via frequency shift, a position offset is generated. Further azimuth four-phase coded periodic modulation results in multiple frequency shift modulations based on this position offset, generating false targets of various orders. Among these, the azimuth... The location of the second-order false target is: ， Orientation The magnitude of the order of false targets is: 。 8. A SAR two-dimensional jamming device based on four-phase coded periodic modulation, characterized in that, include: The receiving module is used to detect and receive signals transmitted by the target SAR system using a jammer, and obtain digital SAR signals after down-conversion and analog-to-digital conversion. The digital SAR signals are then measured and stored. The range modulation module is used to set the period and phase symbols of the range four-phase coded periodic modulation signal according to the interference requirements and digital SAR signal parameters, and to generate the range frequency shift modulation signal based on the range offset. The azimuth modulation module is used to set the period and phase symbols of the azimuth four-phase coded periodic modulation signal according to the interference requirements and digital SAR signal parameters, and to generate the azimuth frequency shift modulation signal based on the azimuth offset. The jamming module is used to obtain a range-modulated SAR signal by performing range modulation in the fast time domain based on a range-direction four-phase coded periodic modulation signal, a range-direction frequency-shift modulation signal, and a digital SAR signal, and to obtain the required digital jamming signal by performing azimuth modulation in the slow time domain based on a azimuth-direction four-phase coded periodic modulation signal, a azimuth-direction frequency-shift modulation signal, and a range-direction modulated SAR signal. The output module is used to forward digital jamming signals to the target SAR system after digital-to-analog conversion and up-conversion, so that different types of two-dimensional jamming effects are generated after imaging processing.

9. An electronic device, characterized in that, include: One or more processors; Memory, used to store one or more programs; When one or more programs are executed by the one or more processors, the one or more processors implement the SAR two-dimensional jamming method based on four-phase coded periodic modulation as described in any one of claims 1-7.

10. A computer-readable storage medium, characterized in that, It stores executable instructions that, when executed by a processor, enable the processor to implement the SAR two-dimensional jamming method based on four-phase coded periodic modulation as described in any one of claims 1-7.

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