Method, device, storage medium and equipment for generating secondary modulation interference signal

Abstract

The present invention discloses a method, device, storage medium and equipment for generating secondary modulation interference signals, and belongs to the field of radar countermeasure technology. The method includes a jammer processing a target SAR signal to obtain a digital SAR signal and calculate signal parameters; combining the required interference type, generating a range phase modulation signal, a range sine function modulation signal, a range frequency shift modulation signal, an azimuth phase modulation signal, an azimuth sine function modulation signal, and an azimuth frequency shift modulation signal according to the signal parameters; according to the generated signals and the digital SAR signal, completing the range modulation and azimuth modulation, and finally obtaining a digital interference signal; converting the digital interference signal into an analog interference signal and forwarding it to the target SAR system, and generating different types of interference effects after imaging processing. The present invention can flexibly generate nine different types of two-dimensional interference effects, and can accurately control the center position of the interference result.

Description

Technical Field

[0001] The present invention belongs to the field of radar countermeasure technology, and in particular relates to a method, device, storage medium and equipment for generating a secondary modulation interference signal. Background Art

[0002] As an active microwave detection device, spaceborne synthetic aperture radar (SAR) can perform all-day, all-weather, long-distance, and high-resolution imaging of ground targets. With the development of imaging technology, synthetic aperture radar has been widely used in civil or military fields such as terrain mapping, weather forecasting, and intelligence reconnaissance. According to the effect of the interference signal, the existing SAR interference can be divided into two categories: suppression interference and deception interference. Among them, suppression interference uses high-power noise signals to cover up the original echo signals of ground targets, and has high power requirements for the jammer. Deception interference modulates the intercepted radar signal according to the detected target SAR system parameters to obtain an interference signal that can produce a false target or scene. It has the advantages of strong flexibility and low interference power requirements. At the same time, it has the disadvantages of complex interference system principles and high precision requirements for parameter reconnaissance. Therefore, smart interference methods with rich research styles and easy implementation have important research value and application prospects.

[0003] In the prior art, Wu Yanhong proposed a multi-dimensional composite modulation interference method for synthetic aperture radar (Chinese patent application number: 202010689237.0). This method combines range delay, phase modulation, Doppler frequency modulation and power control processing methods to modulate the SAR signal, which can achieve four interference effects such as point array and surface target. However, this method can produce fewer interference patterns and cannot flexibly adapt to different application scenarios, which has certain limitations; Wu Qihua proposed a synthetic aperture radar image modulation method based on periodic cyclic phase coding (Chinese patent application number: 202410312770.3), which uses a periodic cyclic phase coding sequence to perform intra-pulse modulation on the target SAR signal, which can produce a range-oriented point array interference effect. However, this image modulation method can only produce a one-dimensional image interference effect, and the interference pattern is single.

[0004] In summary, although the existing phase modulation active jamming method can achieve a two-dimensional jamming effect, it has fewer jamming types and cannot flexibly change the jamming style according to the change of the jamming scene, which has certain limitations. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a method, device, storage medium and equipment for generating a secondary modulated interference signal, which combines two-dimensional frequency shift modulation, azimuth sinusoidal function modulation, azimuth phase modulation, distance sinusoidal function modulation and distance phase modulation, and can flexibly generate nine different types of two-dimensional interference effects, while accurately controlling the center position of the interference result.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0007] A method for generating a secondary modulation interference signal, the method comprising:

[0008] Step 1: The jammer detects and receives the target SAR signal and performs down-conversion processing to obtain an analog SAR signal, samples the analog SAR signal to obtain a digital SAR signal, stores the digital SAR signal and calculates signal parameters;

[0009] Step 2: In combination with the required interference type, the period and duty cycle of the distance-direction periodic phase modulation signal are set according to the signal parameters to generate the required distance-direction phase modulation signal, the modulation coefficient and modulation frequency of the distance-direction sinusoidal function modulation signal are set to generate the distance-direction sinusoidal function modulation signal, and the distance-direction frequency shift amount is set according to the required distance-direction offset to generate the distance-direction frequency shift modulation signal;

[0010] Step three, in combination with the required interference type, set the period and duty cycle of the azimuth periodic phase modulation signal according to the signal parameters to generate the required azimuth phase modulation signal, set the modulation coefficient and modulation frequency of the azimuth sinusoidal function modulation signal to generate the azimuth sinusoidal function modulation signal, and set the azimuth frequency shift amount according to the required azimuth offset to generate the azimuth frequency shift modulation signal;

[0011] Step 4: multiply the generated range phase modulation signal, range sine function modulation signal, and range frequency shift modulation signal in the fast time domain with the digital SAR signal to complete range modulation; multiply the generated azimuth phase modulation signal, azimuth sine function modulation signal, and azimuth frequency shift modulation signal in the slow time domain with the range modulated digital SAR signal to complete azimuth modulation, and finally obtain a digital interference signal;

[0012] Step 5: Convert the digital interference signal into an analog interference signal, up-convert the analog interference signal and forward it to the target SAR system pulse by pulse; then obtain the baseband interference signal through down-conversion and analog-to-digital conversion of the target SAR system; the baseband interference signal is imaged and processed by the target SAR system to produce different types of interference effects.

[0013] On the other hand, the present invention provides a device for generating a secondary modulation interference signal, comprising:

[0014] The parameter acquisition module is used to use the jammer to detect and receive the target SAR signal and perform down-conversion processing to obtain an analog SAR signal, sample the analog SAR signal to obtain a digital SAR signal, store the digital SAR signal and calculate the signal parameters;

[0015] A first signal generating module is used to set the period and duty cycle of the distance periodic phase modulation signal according to the signal parameters in combination with the required interference type to generate the required distance phase modulation signal, set the modulation coefficient and modulation frequency of the distance sine function modulation signal to generate the distance sine function modulation signal, and set the distance frequency shift amount according to the required distance offset amount to generate the distance frequency shift modulation signal;

[0016] The second signal generating module is used to set the period and duty cycle of the azimuth periodic phase modulation signal according to the signal parameters in combination with the required interference type to generate the required azimuth phase modulation signal, set the modulation coefficient and modulation frequency of the azimuth sinusoidal function modulation signal to generate the azimuth sinusoidal function modulation signal, and set the azimuth frequency shift amount according to the required azimuth offset amount to generate the azimuth frequency shift modulation signal;

[0017] A digital signal generation module is used to multiply the generated range phase modulation signal, range sinusoidal function modulation signal, and range frequency shift modulation signal with the digital SAR signal in the fast time domain to complete range modulation, and to multiply the generated azimuth phase modulation signal, azimuth sinusoidal function modulation signal, and azimuth frequency shift modulation signal with the range-modulated digital SAR signal in the slow time domain to complete azimuth modulation, and finally obtain a digital interference signal;

[0018] The interference generation module is used to convert digital interference signals into analog interference signals, up-convert the analog interference signals and forward them to the target SAR system pulse by pulse; then the baseband interference signals are obtained through down-conversion and analog-to-digital conversion of the target SAR system; the baseband interference signals are processed by imaging of the target SAR system to produce different types of interference effects.

[0019] In a third aspect, the present invention provides a computer-readable storage medium having executable instructions stored thereon, which, when executed by a processor, enables the processor to implement the aforementioned method for generating a secondary modulated interference signal.

[0020] In a fourth aspect, the present invention provides a device, comprising: an antenna unit, a processor unit and a storage unit; the antenna unit is used to receive signals transmitted by a target SAR system and transmit interference signals; the storage unit is used to store one or more programs; wherein, when one or more programs are executed by the one or more processors, the one or more processors implement the aforementioned method for generating a secondary modulated interference signal.

[0021] The beneficial effects of the present invention are:

[0022] The present invention combines two-dimensional frequency shift modulation, azimuth sinusoidal function modulation, azimuth phase sequence modulation, distance sinusoidal function modulation and distance phase sequence modulation, and can flexibly produce nine different types of two-dimensional interference effects. It can flexibly change the interference style according to the change of the interference scene, and can accurately control the center position of the interference result. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The flowchart of the method for generating a secondary modulation interference signal of the present invention;

[0024] Figure 2 This is a typical SAR interference scene diagram;

[0025] Figure 3 It is the time domain waveform diagram of the distance periodic phase modulation signal;

[0026] Figure 4 It is the time domain waveform diagram of the azimuth periodic phase modulation signal;

[0027] Figure 5 This is the simulation result of the echo signal when the jammer is not working;

[0028] Figure 6 A two-dimensional dot matrix interference effect diagram generated by the method for generating a secondary modulation interference signal of the present invention;

[0029] Figure 7 This is an effect diagram of continuous strips in azimuth with equal intervals in distance generated by the method for generating secondary modulation interference signals of the present invention;

[0030] Figure 8 This is an effect diagram of the azimuthally discontinuous strips distributed at equal intervals in the distance direction generated by the method for generating the secondary modulation interference signal of the present invention;

[0031] Fig. 9 This is an effect diagram of continuous strips in the distance direction that are equally spaced in the azimuth direction and generated by the method for generating a secondary modulation interference signal of the present invention;

[0032] Fig.10 This is an effect diagram of the discontinuous strips in the distance direction that are equally spaced in the azimuth direction and generated by the method for generating the secondary modulation interference signal of the present invention;

[0033] Fig.11 A two-dimensional surface target interference effect diagram generated by the method for generating a secondary modulation interference signal of the present invention;

[0034] Fig.12 This is an effect diagram of continuous wide strips in azimuth with equal intervals in distance generated by the method for generating secondary modulation interference signals of the present invention;

[0035] Fig.13 This is a two-dimensional target array interference effect diagram generated by the method for generating a secondary modulation interference signal of the present invention;

[0036] Fig.14 This is a diagram of continuous wide-strip interference effect in the distance direction with equal intervals in the azimuth direction generated by the method for generating the secondary modulation interference signal of the present invention;

[0037] Fig.15 This is a framework diagram of a device for generating a secondary modulation interference signal according to the present invention. DETAILED DESCRIPTION

[0038] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0039] The present invention discloses a method for generating a synthetic aperture radar jamming signal based on two-dimensional frequency shift modulation, azimuth sinusoidal function modulation, azimuth phase modulation, range sinusoidal function modulation and range phase modulation. Specifically, Figure 1 FIG. 1 is a flow chart of a method for generating a secondary modulation interference signal according to the present invention, comprising the following steps:

[0040] Step 1: The jammer first detects and receives the target SAR system's transmitted signal, and at the same time down-converts the intercepted SAR signal to obtain an analog 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 the signal parameters including bandwidth, pulse width, frequency modulation slope, and pulse repetition period, and stores the digital SAR signal.

[0041] Step 2: In combination with the required interference type, set the period and duty cycle of the distance periodic phase modulation signal according to the signal parameters to generate the required distance phase modulation signal, set the modulation coefficient and modulation frequency of the distance sinusoidal function modulation signal to generate the distance sinusoidal function modulation signal, and set the distance frequency shift amount according to the required distance offset to generate the distance frequency shift modulation signal.

[0042] Step three: In combination with the required interference type, set the period and duty cycle of the azimuth periodic phase modulation signal according to the signal parameters to generate the required azimuth phase modulation signal, set the modulation coefficient and modulation frequency of the azimuth sinusoidal function modulation signal to generate an azimuth sinusoidal function modulation signal, and set the azimuth frequency shift amount according to the required azimuth offset to generate an azimuth frequency shift modulation signal.

[0043] Step 4: Multiply the generated range phase modulation signal, range sinusoidal function modulation signal and range frequency shift modulation signal with the digital SAR signal in the fast time domain to complete the range modulation; multiply the generated azimuth phase modulation signal, azimuth sinusoidal function modulation signal and azimuth frequency shift modulation signal with the range modulated digital SAR signal in the slow time domain to complete the azimuth modulation, and finally obtain the digital interference signal.

[0044] Step 5: The jammer converts the digital interference signal into an analog interference signal through a digital-to-analog converter, then up-converts the analog interference signal and forwards it pulse by pulse to the target SAR system. The target SAR system down-converts the analog interference signal and performs analog-to-digital conversion to obtain a baseband interference signal. The baseband interference signal can produce different types of interference effects after being imaged by the target SAR system.

[0045] The present invention will be described in detail below in conjunction with the accompanying drawings.

[0046] Typical SAR interference scenarios include: Figure 2 As shown, the flight speed of the side-view airborne SAR platform is set to , the flight altitude is , jammer Located at the center of the SAR system imaging swath and with coordinates , taking the SAR flight direction as Axis, vertical upward direction The shortest slant distance from the jammer to the SAR platform is set to , the instantaneous slope distance is , then we can calculate , .

[0047] The specific implementation process of step one is as follows:

[0048] The target SAR system's transmission signal is the target SAR signal The expression is as follows:

[0049]

[0050] Among them, rect(•) is the rectangular window function, is the distance to time, is the pulse width, is the carrier frequency, is the frequency modulation slope of the linear frequency modulation signal, Is an imaginary unit.

[0051] The jammer down-converts and samples the intercepted SAR signal to obtain a digital SAR signal. The expression of the digital SAR signal is as follows:

[0052]

[0053] in, is the speed of light, For jammer The instantaneous slant range to the SAR platform, is the azimuth time.

[0054] Furthermore, the digital SAR signal is stored and parameters such as bandwidth, pulse width, frequency modulation slope, pulse repetition period, etc. of the SAR signal are measured.

[0055] The specific implementation process of step 2 is as follows:

[0056] According to the measured signal parameters, set the distance phase modulation code element , and set the code elements to appear alternately, thereby generating a range-direction periodic phase modulation signal. Set the period of the range-direction periodic phase modulation signal to , the duty cycle is , then its time domain waveform is as follows Figure 3 shown.

[0057] The distance-dependent periodic phase modulation signal can be converted into the following form using Fourier series theory:

[0058]

[0059] in, is the harmonic component order of the distance-direction periodic phase modulation signal. At the same time, the distance-direction sinusoidal function modulation signal can be expressed as the following mathematical model:

[0060]

[0061] in, is the range modulation index, is the modulation frequency in the distance direction. According to the series expansion, the above formula can be transformed to obtain:

[0062]

[0063] in, is the harmonic order corresponding to the distance sinusoidal function modulated signal, It is the first-order Bessel function corresponding to the distance sine function modulated signal.

[0064] Therefore, the spectrum of the distance-towards sine function modulated signal can be expressed as:

[0065]

[0066] in, is the distance angular frequency, is the impulse function. From the above formula, we can see that the spectrum of the distance-to-sine function modulated signal contains infinite spectrum components. The amplitude of each harmonic component is proportional to the Bessel function of the corresponding order, and the interval of the harmonic components is determined by the angular frequency of the cosine phase modulation signal. Therefore, the spectrum bandwidth of the distance-to-sine function modulated signal is Estimated by Casson's formula:

[0067]

[0068] In addition, set the distance frequency shift according to the required distance offset And generate a distance frequency shift modulation signal, the expression of which is .

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

[0070] According to the measured signal parameters, set the azimuth phase modulation code element , and set the code elements to appear alternately, thereby generating an azimuth periodic phase modulation signal. Set the period of the azimuth periodic phase modulation signal to , the duty cycle is , then its time domain waveform is as follows Figure 4 shown.

[0071] Using Fourier series theory, the azimuth periodic phase modulation signal can be converted into the following form:

[0072]

[0073] in, is the harmonic component order of the azimuth periodic phase modulation signal. At the same time, the azimuth sinusoidal phase modulation signal can be expressed as the following mathematical model:

[0074]

[0075] in, is the azimuth modulation index, is the azimuth modulation frequency. According to the series expansion, the above formula can be transformed to obtain:

[0076]

[0077] in, is the harmonic order corresponding to the azimuth sinusoidal function modulation signal, is the first-order Bessel function corresponding to the azimuth sine function modulation signal. Therefore, the spectrum of the azimuth sine function modulation signal can be expressed as:

[0078]

[0079] in, is the azimuth angular frequency, is the impulse function. From the above formula, we can see that the spectrum of the azimuth sine function modulation signal contains infinite spectral components. The amplitude of each harmonic component is proportional to the Bessel function of the corresponding order, and the interval of the harmonic components is determined by the angular frequency of the cosine phase modulation signal. Therefore, the spectrum bandwidth of the azimuth sine function modulation signal is Estimated by Casson's formula:

[0080]

[0081] In addition, set the azimuth frequency shift according to the required azimuth offset And generate azimuth frequency shift modulation signal, its expression is .

[0082] The specific implementation process of step 4 is as follows:

[0083] The jammer performs range phase modulation, range sinusoidal function modulation, azimuth phase modulation, azimuth sinusoidal function modulation and two-dimensional frequency shift modulation on the received digital SAR signal, and finally obtains a digital interference signal, whose expression is as follows:

[0084]

[0085] The specific implementation process of step 5 is as follows:

[0086] The jammer converts the digital interference signal into an analog interference signal through a digital-to-analog converter, then up-converts the analog interference signal and forwards it pulse by pulse to the target SAR system. Analysis shows that the baseband interference signal obtained after the analog interference signal is down-converted and processed by the target SAR system through analog-to-digital conversion is expressed as:

[0087]

[0088] The imaging characteristics of the baseband interference signal are analyzed using the RD algorithm. First, the range-to-frequency domain matched filter is used. The baseband interference signal is pulse compressed in the range direction, and then the azimuth frequency domain matched filter is used The baseband interference signal is subjected to azimuth pulse compression processing, and the final imaging result is:

[0089]

[0090] in:

[0091]

[0092]

[0093]

[0094]

[0095] , , , is an intermediate parameter. According to the above results, the distance direction generates a position offset after frequency shift modulation. After further phase modulation, multiple frequency shift modulations will be formed on the basis of the position offset, generating false targets of various orders. The distance of the false target to the center position for:

[0096]

[0097] In addition, when When , the amplitude of zero-order and even-order false targets generated by range phase modulation is zero.

[0098] At the same time, the azimuth direction will produce a position offset after frequency shift modulation, and further after phase modulation, multiple frequency shift modulations will be formed on the basis of the position offset, generating false targets of various orders. The direction of the false target is towards the center for:

[0099]

[0100] In addition, when When , the amplitude of zero-order and even-order false targets generated by azimuth phase modulation is zero.

[0101] The following is a verification analysis of the theoretical model of the present invention in combination with the simulation results. The system works in strip imaging mode, and the working frequency band is Band, center frequency is , the carrier speed is , the signal bandwidth is , the signal time width is , the pulse repetition frequency is According to the simulation parameters, System distance resolution for , azimuth resolution for . Place the jammer at the zero coordinate point. Figure 5 The figure shows the simulation result of the echo signal when the jammer is not working. The jammer imaging result is a point target located at the coordinate zero point. By changing the modulation parameters, different types of jamming effects can be achieved.

[0102] Set the frequency shift in the distance direction to , the azimuth frequency shift is , the period of the distance-direction periodic phase modulation signal is , the duty cycle is , the modulation coefficient of the distance sine function modulated signal for , modulation frequency for , the period of the azimuth periodic phase modulation signal is , the duty cycle is , the modulation coefficient of the azimuth sine function modulation signal for , modulation frequency for According to the theoretical model calculation, the interference result is a two-dimensional dot matrix. The simulation results are as follows: Figure 6 As shown, it is consistent with the theoretical analysis.

[0103] Set the frequency shift in the distance direction to , the azimuth frequency shift is , the period of the distance-direction periodic phase modulation signal is , the duty cycle is , the modulation coefficient of the distance sine function modulated signal for , modulation frequency for , the period of the azimuth periodic phase modulation signal is , the duty cycle is , the modulation coefficient of the azimuth sine function modulation signal for , modulation frequency for According to the theoretical model calculation, the interference result is a continuous strip in the azimuth direction with equal intervals in the distance direction. The simulation results are as follows: Figure 7 As shown, it is consistent with the theoretical analysis.

[0104] Set the frequency shift in the distance direction to , the azimuth frequency shift is , the period of the distance-direction periodic phase modulation signal is , the duty cycle is , the modulation coefficient of the distance sine function modulated signal for , modulation frequency for , the period of the azimuth periodic phase modulation signal is , the duty cycle is , the modulation coefficient of the azimuth sine function modulation signal for , modulation frequency for According to the theoretical model calculation, the interference result is an azimuthally discontinuous strip distributed at equal intervals in the distance direction. The simulation results are as follows: Figure 8 As shown, it is consistent with the theoretical analysis.

[0105] Set the frequency shift in the distance direction to , the azimuth frequency shift is , the period of the distance-direction periodic phase modulation signal is , the duty cycle is , the modulation coefficient of the distance sine function modulated signal for , modulation frequency for , the period of the azimuth periodic phase modulation signal is , the duty cycle is , the modulation coefficient of the azimuth sine function modulation signal for , modulation frequency for According to the theoretical model calculation, the interference result is a continuous strip in the distance with equal intervals in the azimuth direction. The simulation results are as follows: Fig. 9 As shown, it is consistent with the theoretical analysis.

[0106] Set the frequency shift in the distance direction to , the azimuth frequency shift is , the period of the distance-direction periodic phase modulation signal is , the duty cycle is , the modulation coefficient of the distance sine function modulated signal for , modulation frequency for , the period of the azimuth periodic phase modulation signal is , the duty cycle is , the modulation coefficient of the azimuth sine function modulation signal for , modulation frequency for According to the theoretical model calculation, the interference result is a discontinuous strip in the distance with equal intervals in the azimuth direction. The simulation results are as follows: Fig.10 As shown, it is consistent with the theoretical analysis.

[0107] Set the frequency shift in the distance direction to , the azimuth frequency shift is , the period of the distance-direction periodic phase modulation signal is , the duty cycle is , the modulation coefficient of the distance sine function modulated signal for , modulation frequency for , the period of the azimuth periodic phase modulation signal is , the duty cycle is , the modulation coefficient of the azimuth sine function modulation signal for , modulation frequency for According to the theoretical model calculation, the interference result is a two-dimensional surface target. The simulation results are as follows: Fig.11 As shown, it is consistent with the theoretical analysis.

[0108] Set the frequency shift in the distance direction to , the azimuth frequency shift is , the period of the distance-direction periodic phase modulation signal is , the duty cycle is , the modulation coefficient of the distance sine function modulated signal for , modulation frequency for , the period of the azimuth periodic phase modulation signal is , the duty cycle is , the modulation coefficient of the azimuth sine function modulation signal for , modulation frequency for According to the theoretical model calculation, the interference result is a continuous wide strip in the azimuth direction with equal intervals in the distance direction. The simulation results are as follows: Fig.12 As shown, it is consistent with the theoretical analysis.

[0109] Set the frequency shift in the distance direction to , the azimuth frequency shift is , the period of the distance-direction periodic phase modulation signal is , the duty cycle is , the modulation coefficient of the distance sine function modulated signal for , modulation frequency for , the period of the azimuth periodic phase modulation signal is , the duty cycle is , the modulation coefficient of the azimuth sine function modulation signal for , modulation frequency for According to the theoretical model calculation, the interference result is a two-dimensional target array. The simulation results are as follows: Fig.13 As shown, it is consistent with the theoretical analysis.

[0110] Set the frequency shift in the distance direction to , the azimuth frequency shift is , the period of the distance-direction periodic phase modulation signal is , the duty cycle is , the modulation coefficient of the distance sine function modulated signal for , modulation frequency for , the period of the azimuth periodic phase modulation signal is , the duty cycle is , the modulation coefficient of the azimuth sine function modulation signal for , modulation frequency for According to the theoretical model calculation, the interference result is a continuous wide strip in the distance direction with equal intervals in the azimuth direction. The simulation results are as follows: Fig.14 As shown, it is consistent with the theoretical analysis.

[0111] Therefore, the novel SAR jamming method proposed in the present invention can realize smart two-dimensional jamming of SAR images, ultimately producing nine different types of jamming effects, and can precisely adjust the center position of the jamming result, and its effectiveness has been proven.

[0112] On the other hand, the present invention provides a device for generating a secondary modulation interference signal, comprising:

[0113] The parameter acquisition module is used to use the jammer to detect and receive the target SAR signal and perform down-conversion processing to obtain an analog SAR signal, sample the analog SAR signal to obtain a digital SAR signal, store the digital SAR signal and calculate the signal parameters;

[0114] A first signal generating module is used to set the period and duty cycle of the distance periodic phase modulation signal according to the signal parameters in combination with the required interference type to generate the required distance phase modulation signal, set the modulation coefficient and modulation frequency of the distance sine function modulation signal to generate the distance sine function modulation signal, and set the distance frequency shift amount according to the required distance offset amount to generate the distance frequency shift modulation signal;

[0115] The second signal generating module is used to set the period and duty cycle of the azimuth periodic phase modulation signal according to the signal parameters in combination with the required interference type to generate the required azimuth phase modulation signal, set the modulation coefficient and modulation frequency of the azimuth sinusoidal function modulation signal to generate the azimuth sinusoidal function modulation signal, and set the azimuth frequency shift amount according to the required azimuth offset amount to generate the azimuth frequency shift modulation signal;

[0116] A digital signal generation module is used to multiply the generated range phase modulation signal, range sinusoidal function modulation signal, and range frequency shift modulation signal with the digital SAR signal in the fast time domain to complete range modulation, and to multiply the generated azimuth phase modulation signal, azimuth sinusoidal function modulation signal, and azimuth frequency shift modulation signal with the range-modulated digital SAR signal in the slow time domain to complete azimuth modulation, and finally obtain a digital interference signal;

[0117] The interference generation module is used to convert digital interference signals into analog interference signals, up-convert the analog interference signals and forward them to the target SAR system pulse by pulse; then the baseband interference signals are obtained through down-conversion and analog-to-digital conversion of the target SAR system; the baseband interference signals are processed by imaging of the target SAR system to produce different types of interference effects.

[0118] Specifically, Fig.15As shown, a device for generating a two-dimensional modulated interference signal of the present invention comprises: a signal detection module, which is used for detecting and receiving the target SAR system transmission signal; a down-conversion module, which is used for down-conversion processing of the intercepted SAR signal; an analog-to-digital conversion module, which samples and processes the target system SAR transmission signal received by the detection and converts it into a digital signal; a signal parameter measurement module, which is used for measuring the pulse width, bandwidth, pulse repetition frequency and other signal parameters of the received intercepted SAR signal; a range phase modulation module, which is used for generating a range periodic phase modulation signal and performing intra-pulse modulation on the digital signal; a range sinusoidal function modulation module, which is used for generating a range sinusoidal function modulation signal and performing intra-pulse modulation on the digital signal; The module is used to generate a frequency-shift modulation signal in the direction of azimuth and perform intra-pulse modulation on the digital signal; the module is used to generate a periodic phase modulation signal in the direction of azimuth and perform inter-pulse modulation on the digital signal; the module is used to generate a sinusoidal function modulation signal in the direction of azimuth and perform inter-pulse modulation on the digital signal; the module is used to generate a frequency-shift modulation signal in the direction of azimuth and perform inter-pulse modulation on the digital signal; the module is used to generate a frequency-shift modulation signal in the direction of azimuth and perform inter-pulse modulation on the digital signal; the module is used to generate a frequency-shift modulation signal in the direction of azimuth and perform inter-pulse modulation on the digital signal; the module is used to convert the modulated digital interference signal into an analog interference signal; the module is used to perform up-conversion on the analog interference signal; the transmitting module is used to transmit the analog interference signal pulse by pulse.

[0119] In a third aspect, the present invention provides a computer-readable storage medium having executable instructions stored thereon, which, when executed by a processor, enables the processor to implement the aforementioned method for generating a secondary modulated interference signal.

[0120] In a fourth aspect, the present invention provides a device, comprising: an antenna unit, a processor unit and a storage unit; the antenna unit is used to receive signals transmitted by a target SAR system and transmit interference signals; the storage unit is used to store one or more programs; wherein, when one or more programs are executed by the one or more processors, the one or more processors implement the aforementioned method for generating a secondary modulated interference signal.

[0121] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is 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 in the scope of protection of the present invention.

Claims

1. A method for generating a secondary modulation interference signal, characterized in that: The method comprises: Step 1: The jammer detects and receives the target SAR signal and performs down-conversion processing to obtain an analog SAR signal, samples the analog SAR signal to obtain a digital SAR signal, stores the digital SAR signal and calculates signal parameters; Step 2: In combination with the required interference type, the period and duty cycle of the distance-direction periodic phase modulation signal are set according to the signal parameters to generate the required distance-direction phase modulation signal, the modulation coefficient and modulation frequency of the distance-direction sinusoidal function modulation signal are set to generate the distance-direction sinusoidal function modulation signal, and the distance-direction frequency shift amount is set according to the required distance-direction offset to generate the distance-direction frequency shift modulation signal; Step three, in combination with the required interference type, set the period and duty cycle of the azimuth periodic phase modulation signal according to the signal parameters to generate the required azimuth phase modulation signal, set the modulation coefficient and modulation frequency of the azimuth sinusoidal function modulation signal to generate the azimuth sinusoidal function modulation signal, and set the azimuth frequency shift amount according to the required azimuth offset to generate the azimuth frequency shift modulation signal; Step 4: multiply the generated range phase modulation signal, range sine function modulation signal, and range frequency shift modulation signal in the fast time domain with the digital SAR signal to complete range modulation; multiply the generated azimuth phase modulation signal, azimuth sine function modulation signal, and azimuth frequency shift modulation signal in the slow time domain with the range modulated digital SAR signal to complete azimuth modulation, and finally obtain a digital interference signal; Step 5: Convert the digital interference signal into an analog interference signal, up-convert the analog interference signal and forward it to the target SAR system pulse by pulse; then obtain the baseband interference signal through down-conversion and analog-to-digital conversion of the target SAR system; the baseband interference signal is imaged and processed by the target SAR system to produce different types of interference effects.

2. The method for generating a secondary modulation interference signal according to claim 1, characterized in that: The step 1 includes: the transmission signal of the target SAR system is the target SAR signal The expression is as follows: Among them, rect(•) is the rectangular window function, is the distance to time, is the pulse width, is the carrier frequency, is the frequency modulation slope of the linear frequency modulation signal, is an imaginary unit; The jammer performs down-conversion and sampling processing on the intercepted SAR signal to obtain a digital SAR signal, where the expression of the digital SAR signal is as follows: in, is the speed of light, For jammer The instantaneous slant range to the SAR platform, is the azimuth time; The digital SAR signal is stored and the bandwidth, pulse width, frequency modulation slope, and pulse repetition period parameters of the digital SAR signal are measured.

3. The method for generating a secondary modulation interference signal according to claim 2, characterized in that: The second step comprises: According to the measured signal parameters, set the distance phase modulation code element Alternately, generate a distance phase modulation signal, and set the period of the distance phase modulation signal to , the duty cycle is , using Fourier series theory to convert the distance periodic phase modulation signal into the following form: in, is the order of harmonic component of the distance phase modulation signal; The distance-directed sinusoidal function modulated signal is expressed as: in, is the range modulation index, is the range modulation frequency; Set the frequency shift in the distance And generate a distance frequency shift modulation signal, the expression of which is .

4. The method for generating a secondary modulation interference signal according to claim 3, characterized in that: The spectrum of the distance-directed sinusoidal function modulated signal is expressed as: in, is the harmonic order corresponding to the distance sinusoidal function modulated signal, is the first-order Bessel function corresponding to the distance sinusoidal function modulation signal, is the distance angular frequency, is the impulse function; Spectral bandwidth of the distance-dependent sine-modulated signal Estimated by Casson's formula.

5. The method for generating a secondary modulation interference signal according to claim 4, characterized in that: The step three comprises: According to the measured signal parameters, set the azimuth phase modulation code element When they appear alternately, an azimuth periodic phase modulation signal is generated, and the period of the azimuth periodic phase modulation signal is set to , the duty cycle is , using Fourier series theory, the azimuth periodic phase modulation signal is converted into the following form: in, is the order of harmonic component of azimuth periodic phase modulation signal; The azimuth sinusoidal function phase modulation signal is expressed as the following mathematical model: in, is the azimuth modulation index, is the azimuth modulation frequency; Set the azimuth frequency shift according to the required azimuth offset And generate azimuth frequency shift modulation signal, its expression is .

6. The method for generating a secondary modulation interference signal according to claim 5, characterized in that: The fourth step comprises: The jammer performs range phase modulation, range sinusoidal function modulation, azimuth phase modulation, azimuth sinusoidal function modulation and two-dimensional frequency shift modulation on the received digital SAR signal, and finally obtains a digital interference signal, whose expression is as follows: (13)。 7. The method for generating a secondary modulation interference signal according to claim 1, characterized in that: The step five comprises: The baseband interference signal is subjected to range pulse compression processing and azimuth pulse compression processing in sequence by using a range frequency domain matching filter and an azimuth frequency domain matching filter respectively, thereby generating position offsets and false targets of various orders.

8. A device for generating a secondary modulation interference signal, characterized in that: include: The parameter acquisition module is used to use the jammer to detect and receive the target SAR signal and perform down-conversion processing to obtain an analog SAR signal, sample the analog SAR signal to obtain a digital SAR signal, store the digital SAR signal and calculate the signal parameters; A first signal generating module is used to set the period and duty cycle of the distance periodic phase modulation signal according to the signal parameters in combination with the required interference type to generate the required distance phase modulation signal, set the modulation coefficient and modulation frequency of the distance sine function modulation signal to generate the distance sine function modulation signal, and set the distance frequency shift amount according to the required distance offset amount to generate the distance frequency shift modulation signal; The second signal generating module is used to set the period and duty cycle of the azimuth periodic phase modulation signal according to the signal parameters in combination with the required interference type to generate the required azimuth phase modulation signal, set the modulation coefficient and modulation frequency of the azimuth sinusoidal function modulation signal to generate the azimuth sinusoidal function modulation signal, and set the azimuth frequency shift amount according to the required azimuth offset amount to generate the azimuth frequency shift modulation signal; A digital signal generation module is used to multiply the generated range phase modulation signal, range sinusoidal function modulation signal, and range frequency shift modulation signal with the digital SAR signal in the fast time domain to complete range modulation, and to multiply the generated azimuth phase modulation signal, azimuth sinusoidal function modulation signal, and azimuth frequency shift modulation signal with the range-modulated digital SAR signal in the slow time domain to complete azimuth modulation, and finally obtain a digital interference signal; The interference generation module is used to convert digital interference signals into analog interference signals, up-convert the analog interference signals and forward them to the target SAR system pulse by pulse; then the baseband interference signals are obtained through down-conversion and analog-to-digital conversion of the target SAR system; the baseband interference signals are processed by imaging of the target SAR system to produce different types of interference effects.

9. A computer-readable storage medium, characterized in that: Executable instructions are stored thereon, and when the instructions are executed by a processor, the processor can implement a method for generating a secondary modulated interference signal as described in any one of claims 1-7.

10. A communication device, characterized in that: include: Antenna unit, processor unit and storage unit; The antenna unit is used to receive the target SAR system transmission signal and transmit an interference signal; The storage unit is used to store one or more programs; Wherein, when one or more programs are executed by the one or more processors, the one or more processors implement a method for generating a secondary modulated interference signal as described in any one of claims 1-7.

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