An active electronic camouflage jamming method against spaceborne SAR reconnaissance

Abstract

The application discloses a kind of active electronic camouflage jamming methods to resist spaceborne SAR reconnaissance, S1, the electromagnetic camouflage period of considering topographic information is solved;S2, the electromagnetic signal generation of false target based on scattering distribution increment;S3, carry out distributed networking interference;First, the camouflage interference period is solved in combination with topographic information, the target background template is established according to existing radar image information, the interference information of false target is generated using the mode of scattering distribution increment, finally, the interference information is modulated into radar signal emission using distributed networking interference mode, the problems such as error accumulation generated by SAR motion parameter and signal parameter estimation are solved, and the fidelity and timeliness of electromagnetic camouflage are improved.

Description

Technical Field

[0001] This invention belongs to the field of radar signal transmission technology, and specifically relates to an active electronic camouflage jamming method for countering spaceborne SAR reconnaissance. Background Technology

[0002] Synthetic Aperture Radar (SAR) is an active microwave imaging radar capable of monitoring targets at all times, in all weather conditions, and at long distances, with high resolution in both range and azimuth directions. As the ability of spaceborne SAR to acquire target information continues to improve, active electronic camouflage methods targeting the imaging characteristics of spaceborne SAR are constantly being refined. This method primarily utilizes a signal jammer to receive radar signals transmitted by the target radar, modulates these signals in the phase or frequency domain, and then transmits the modulated signal. When the radar receives the modulated radar echo signal and performs radar imaging, it generates a camouflaged false target, thus achieving a camouflage effect.

[0003] For active electronic camouflage methods, Wang Shengli proposed a frequency domain implementation method for electromagnetic camouflage interference of SAR signals, which improves real-time processing efficiency; Zhou Feng et al. proposed multiple interference models for electromagnetic camouflage interference of SAR signals, such as optimized scattered wave interference, large scene interference and electromagnetic interference; Chen Siwei et al. proposed an approximate processing method for electromagnetic camouflage interference based on DRFM.

[0004] The analysis of SAR electromagnetic camouflage jamming technology mainly focuses on two types of objects: one is the SAR scene, and the other is the SAR target. Examples include adding fake vehicles to a uniform surface or transforming farmland into forest. The similarity between the modulated signal and the real signal directly affects the final camouflage effect. The modulated signal relies on the accurate acquisition of the target's scattering distribution characteristics, the detection radar system parameters, and the relative motion relationship between the radar and the target. The challenge of camouflage technology targeting both SAR scenes and SAR targets lies in how to accurately obtain the radar system parameters and the parameter information of the transmitted signal.

[0005] Chang Xin et al. discussed the problem of reducing deception interference, proposing a deception interference method based on two-dimensional separation to expand the main lobe width and generate a low-resolution mosaic scene. Lin Xiaohong et al. proposed the WK algorithm, which can quickly convert radar grayscale scene images into interference signals. The jammer then transmits interference signals line by line in the SAR sidelobe region, interfering with important features of the real SAR image in real time. Shi Yunqi proposed a deception interference technique based on scattering distribution increments, adjusting the template size of the block stitching synthesis technique to obtain false scenes with high similarity. Zhao Bo et al. proposed the idea of ​​theoretical multi-receiver to reduce the dependence on SAR trajectory parameters, solving the problem of error amplification in the linear equation system in the interference coefficient calculation. Wang Miaomiao improved the SAR deception interference algorithm based on scattering distribution increments, solving the problem of some increments being negative.

[0006] Currently, SAR electronic camouflage methods typically involve directly superimposing false scenes onto real scenes to create deceptive scenarios. However, based on speckle models, the deceptive and real scenes are randomly superimposed, not simply a sum of scattering coefficients. This results in low similarity between the generated deceptive and false target scenes, making the camouflage signals easily detectable. Furthermore, in generating spaceborne SAR electromagnetic camouflage signals, the instantaneous position information of the target and the SAR platform is a key parameter affecting the effectiveness of the camouflage signal. To improve efficiency, a second-order Taylor series expansion of the slant range is often used. However, this method introduces and accumulates errors from inaccurate parameter estimations of various SAR platforms during parameter estimation, reducing the realism of the electromagnetic camouflage and resulting in poor robustness against electromagnetic camouflage interference. Summary of the Invention

[0007] The purpose of this invention is to provide an active electronic camouflage jamming method to counter spaceborne SAR reconnaissance, so as to solve the problems mentioned in the background art.

[0008] To achieve the above objectives, the present invention provides the following technical solution: an active electronic camouflage jamming method for countering spaceborne SAR reconnaissance, characterized by the following specific steps:

[0009] S1. Electromagnetic camouflage time period calculation considering terrain information: Read the DEM model data of the center position and surrounding area of ​​the target area, and then calculate the camouflage time setting duration.

[0010] S2. Generation of false target electromagnetic signals based on scattering distribution increment: The signal is down-converted by the radar signal receiver, then processed further, and then up-converted to the carrier frequency for retransmission.

[0011] S3. Distributed network jamming: Use one jammer as the main station of the transceiver unit, and deploy several receivers as auxiliary stations for receiving radar signals. Perform down-conversion processing on the received SAR signals, then process and disguise the SAR signals, and finally perform up-conversion processing and transmit.

[0012] Preferably, the specific operation of step S1 is as follows:

[0013] Step S101: Read the center location of the target area and the surrounding DEM model data, calculate the elevation angle between the highest point of the ground feature and the target area under different azimuth angles, and use this value as the terrain cutoff height threshold.

[0014] Step S102: Dynamically set satellite orbit parameters and sensor imaging angle range using self-developed software to obtain instantaneous geometric information between the satellite and the target;

[0015] Step S103: Compare whether the instantaneous elevation angle between the satellite and the target simultaneously satisfies the sensor imaging angle and the terrain cutoff height threshold. Use linear interpolation to calculate the critical moment that satisfies the elevation angle condition, and use the critical moment to calculate the effective duration of radar imaging in the target area.

[0016] Step S104: Calculate the camouflage time setting and perform electromagnetic signal camouflage based on the effective time of satellite overhead.

[0017] Preferably, the specific operation of step S2 is as follows:

[0018] Step S201: After the radar signal receiver undergoes down-conversion processing, it is sampled by the analog-to-digital converter and stored in the digital radio frequency memory. The existing radar image data is used to correct the energy of the target radar detection unit and the detection radar detection unit. The radar energy is modified and modulated according to the radar system processing gain and loss parameters to serve as the background scene. A target template is selected from the target template library.

[0019] Step S202: Using texture synthesis technology, the template target and background scene are textured and adjusted according to parameters such as radar system gain to generate a virtual background. Based on the virtual background, the difference in backscattering coefficients between the real scene and the virtual scene target is calculated. Since obvious edge marks are easily seen at the edges between the virtual target and the real scene, a smooth attenuation process is adopted. Two smooth transition functions are used from left to right and from top to bottom, one is an attenuation function and the other is an increasing function, to effectively fuse the background in the boundary area and obtain the target background feature parameters after edge processing.

[0020] Step S203: Simultaneously, calculate the shadow area of ​​the real target, and based on the position of the shadow point and the backscattering coefficient of the superimposed background, obtain the modulation term that is not related to the azimuth fast time, perform azimuth modulation on the signal, and obtain the interference signal characteristic parameters by weighted summation.

[0021] Step S204: Process each captured pulse sample using a programmable target integrated circuit, perform delay processing, and use a series of complex range modulators to modulate and generate electromagnetic signals for camouflage backgrounds;

[0022] Step S205: Use a digital-to-analog converter to convert the digital signal into an analog signal, and then up-convert it to a carrier frequency for retransmission.

[0023] Preferably, the specific operation method of step S3 is as follows:

[0024] Take O jamEstablish an interference scene coordinate system parallel to the radar platform coordinate system, centered on the radar platform coordinate system. The triangle represents the jamming auxiliary station used to intercept SAR signals. The blue dashed line represents the actual movement trajectory of the SAR platform. Each time t of the SAR platform... a The coordinates are:

[0025] T s (t a )=(u s v s w s ) T

[0026] Assuming there are N auxiliary stations, using rec i If the coordinates are expressed as follows, then the coordinates are...

[0027] rec i =(u i v i w i ) T

[0028] Where i represents the i-th receiver, whose coordinate position relative to the master station jammer is known;

[0029] The instantaneous slant range between the main station jammer (jam) and the SAR platform is:

[0030]

[0031] The instantaneous slant range between the i-th receiver and the SAR platform is:

[0032]

[0033] The distance difference between the receiver and the master station jam

[0034] Due to the large-scale time differences of SAR in the range and azimuth directions, the relative distance between different receiving stations and the SAR is calculated at each slow time t. a Estimate the location of the SAR platform and lock the SAR in the correct position;

[0035] AT s =KR d ||T s ||

[0036]

[0037]

[0038]

[0039] In the formula, A is the receiver position matrix, and K and Rd are matrix constants;

[0040] Since there is only one unknown variable, the coordinates of the SAR platform can be accurately determined by deploying three or more receivers.

[0041] T S =(A T A)A T (KR d ||T s ||)

[0042] By using the calculated location information to compensate for radar signal time delay, a deception jamming signal can be generated.

[0043]

[0044] Compared with the prior art, the beneficial effects of the present invention are:

[0045] This invention first calculates the camouflage interference period by combining terrain information, establishes a target background template based on existing radar image information, generates interference information of false targets using a scattering distribution increment mode, and finally modulates the interference information into radar signals for transmission using a distributed network interference method. This solves the problems of error accumulation caused by separately estimating SAR motion parameters and signal parameters, and improves the realism and timeliness of electromagnetic camouflage. Attached Figure Description

[0046] Figure 1 This is a flowchart illustrating the process of generating electromagnetic signals for false targets based on scattering distribution increments according to the present invention.

[0047] Figure 2 This is a simplified schematic diagram of the distributed networking layout structure of the present invention;

[0048] Figure 3 This is a flowchart illustrating the process of generating interference spoofing signals through distributed networking according to the present invention. Detailed Implementation

[0049] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0050] Example

[0051] Please see Figure 1-3This invention provides a technical solution: an active electronic camouflage jamming method for countering spaceborne SAR reconnaissance, characterized by the following specific steps:

[0052] S1. Electromagnetic camouflage time period calculation considering terrain information: Read the DEM model data of the center position and surrounding area of ​​the target area, and then calculate the camouflage time setting duration.

[0053] S2. Generation of false target electromagnetic signals based on scattering distribution increment: The signal is down-converted by the radar signal receiver, then processed further, and then up-converted to the carrier frequency for retransmission.

[0054] S3. Distributed network jamming: Use one jammer as the main station of the transceiver unit, and deploy several receivers as auxiliary stations for receiving radar signals. Perform down-conversion processing on the received SAR signals, then process and disguise the SAR signals, and finally perform up-conversion processing and transmit.

[0055] Specifically, the specific operation of step S1 is as follows:

[0056] Step S101: Read the center location of the target area and the surrounding DEM model data, calculate the elevation angle between the highest point of the ground feature and the target area under different azimuth angles, and use this value as the terrain cutoff height threshold.

[0057] Step S102: Dynamically set satellite orbit parameters and sensor imaging angle range using self-developed software to obtain instantaneous geometric information between the satellite and the target;

[0058] Step S103: Compare whether the instantaneous elevation angle between the satellite and the target simultaneously satisfies the sensor imaging angle and the terrain cutoff height threshold. Use linear interpolation to calculate the critical moment that satisfies the elevation angle condition, and use the critical moment to calculate the effective duration of radar imaging in the target area.

[0059] Step S104: Calculate the camouflage time setting and perform electromagnetic signal camouflage based on the effective time of satellite overhead.

[0060] Specifically, step S2 is performed as follows:

[0061] Step S201: After the radar signal receiver undergoes down-conversion processing, it is sampled by the analog-to-digital converter and stored in the digital radio frequency memory. The existing radar image data is used to correct the energy of the target radar detection unit and the detection radar detection unit. The radar energy is modified and modulated according to the radar system processing gain and loss parameters to serve as the background scene. A target template is selected from the target template library.

[0062] Step S202: Using texture synthesis technology, the template target and background scene are textured and adjusted according to parameters such as radar system gain to generate a virtual background. Based on the virtual background, the difference in backscattering coefficients between the real scene and the virtual scene target is calculated. Since obvious edge marks are easily seen at the edges between the virtual target and the real scene, a smooth attenuation process is adopted. Two smooth transition functions are used from left to right and from top to bottom, one is an attenuation function and the other is an increasing function, to effectively fuse the background in the boundary area and obtain the target background feature parameters after edge processing.

[0063] Step S203: Simultaneously, calculate the shadow area of ​​the real target, and based on the position of the shadow point and the backscattering coefficient of the superimposed background, obtain the modulation term that is not related to the azimuth fast time, perform azimuth modulation on the signal, and obtain the interference signal characteristic parameters by weighted summation.

[0064] Step S204: Process each captured pulse sample using a programmable target integrated circuit, perform delay processing, and use a series of complex range modulators to modulate and generate electromagnetic signals for camouflage backgrounds;

[0065] Step S205: Use a digital-to-analog converter to convert the digital signal into an analog signal, and then up-convert it to a carrier frequency for retransmission.

[0066] Specifically, the operation method for step S3 is as follows:

[0067] Take O jam Establish an interference scene coordinate system parallel to the radar platform coordinate system, centered on the radar platform coordinate system. The triangle represents the jamming auxiliary station used to intercept SAR signals. The blue dashed line represents the actual movement trajectory of the SAR platform. Each time t of the SAR platform... a The coordinates are:

[0068] T s (t a )=(u s v s w s ) T

[0069] Assuming there are N auxiliary stations, using rec i If the coordinates are expressed as follows, then the coordinates are...

[0070] rec i =(u i v i w i ) T

[0071] Where i represents the i-th receiver, whose coordinate position relative to the master station jammer is known;

[0072] The instantaneous slant range between the main station jammer (jam) and the SAR platform is:

[0073]

[0074] The instantaneous slant range between the i-th receiver and the SAR platform is:

[0075]

[0076] The distance difference between the receiver and the master station jam

[0077] Due to the large-scale time differences of SAR in the range and azimuth directions, the relative distance between different receiving stations and the SAR is calculated at each slow time t. a Estimate the location of the SAR platform and lock the SAR in the correct position;

[0078] AT s =KR d ||T s ||

[0079]

[0080]

[0081]

[0082] In the formula, A is the receiver position matrix, and K and Rd are matrix constants;

[0083] Since there is only one unknown variable, the coordinates of the SAR platform can be accurately determined by deploying three or more receivers.

[0084] T S =(A T A)A T (KR d ||T s ||)

[0085] By using the calculated location information to compensate for radar signal time delay, a deception jamming signal can be generated.

[0086]

[0087] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for active electronic camouflage jamming to counter spaceborne SAR reconnaissance, characterized in that, The specific steps are as follows: S1. Electromagnetic camouflage time period calculation considering terrain information: Read the DEM model data of the center location and surrounding area of ​​the target area, and then calculate the set duration of the camouflage time. The specific operation is as follows: Step S101: Read the center location of the target area and the surrounding DEM model data, calculate the elevation angle between the highest point of the ground feature and the target area under different azimuth angles, and use this value as the terrain cutoff height threshold. Step S102: Dynamically set satellite orbit parameters and sensor imaging angle range using self-developed software to obtain instantaneous geometric information between the satellite and the target; Step S103: Compare whether the instantaneous elevation angle between the satellite and the target simultaneously satisfies the sensor imaging angle and the terrain cutoff height threshold. Use linear interpolation to calculate the critical moment that satisfies the elevation angle condition, and use the critical moment to calculate the effective duration of radar imaging in the target area. Step S104: Calculate the camouflage time setting and perform electromagnetic signal camouflage based on the effective time of satellite overhead; S2. Generation of false target electromagnetic signals based on scattering distribution increment: The signal is down-converted by the radar signal receiver, then further processed, and finally up-converted to the carrier frequency for retransmission. The specific operation is as follows: Step S201: After the radar signal receiver undergoes down-conversion processing, it is sampled by the analog-to-digital converter and stored in the digital radio frequency memory. The existing radar image data is used to correct the energy of the target radar detection unit and the detection radar detection unit. The radar energy is modified and modulated according to the radar system processing gain and loss parameters to serve as the background scene. A target template is selected from the target template library. Step S202: Use texture synthesis technology to synthesize the template target and background scene textures, adjust the amplitude according to the radar system gain parameters to generate a virtual background, and calculate the backscattering coefficient difference between the real scene and the virtual scene target based on the virtual background. Since obvious edge marks are easy to appear at the edge part between the virtual target and the real scene, a smooth attenuation process is adopted. Two smooth transition functions are used from left to right and from top to bottom, one is an attenuation function and the other is an increasing function, and then effective background fusion is performed in the boundary area to obtain the target background feature parameters after edge processing. Step S203: Simultaneously, calculate the shadow area of ​​the real target, and based on the shadow point position and the backscattering coefficient of the superimposed background, obtain the modulation term that is not related to the azimuth fast time, perform azimuth modulation on the signal, and obtain the interference signal characteristic parameters by weighted summation. Step S204: Process each captured pulse sample using a programmable target integrated circuit, perform delay processing, and use a range modulator to modulate and generate an electromagnetic signal for camouflage background; Step S205: Use a digital-to-analog converter to convert the digital signal into an analog signal, then up-convert it to a carrier frequency and retransmit it; S3. Distributed network jamming: Use one jammer as the main station of the transceiver unit, and deploy several receivers as auxiliary stations for receiving radar signals. Perform down-conversion processing on the received SAR signals, then process and disguise the SAR signals, and finally perform up-conversion processing and transmit.

2. The active electronic camouflage jamming method for countering spaceborne SAR reconnaissance according to claim 1, characterized in that: The specific operation method for step S3 is as follows: by Establish an interference scene coordinate system parallel to the radar platform coordinate system, centered on the SAR platform, for each time period. The coordinates are: ； In the formula, Represents a coordinate vector. These are the coordinate components of the SAR platform, and T represents the transpose of the coordinate vector. Assuming there are N auxiliary stations, using If the coordinates are: ； Where i represents the i-th receiver. These are the coordinate components of the jammer in the SAR platform coordinate system, and their coordinate positions relative to the master station jammer are known. The instantaneous slant range between the main station jammer (jam) and the SAR platform is: ； The instantaneous slant range between the i-th receiver and the SAR platform is: ； The distance difference between the receiver and the master station jam ; Due to the large-scale time differences of SAR in the range and azimuth directions, the relative distance between different receiving stations and the SAR is considered at each time step. Estimate the location of the SAR platform and lock the SAR in the correct position; ； ； ； ； In the formula, For receiver position matrix, and These are the matrix constants; Since there is only one unknown variable, the coordinates of the SAR platform can be accurately determined by deploying three or more receivers. ； By using the calculated location information to compensate for radar signal time delay, a deception jamming signal can be generated. ； In the formula, This indicates a deception or interference signal. For radar pulse fast time, Radar pulse slow time, For the instantaneous slant range that the radar needs to compensate for, Convolution operators for radar signals Let c be the coordinate components of the jammer in the SAR platform coordinate system, and c be the speed of light. For radar signal carrier frequency, Indicates the phase term.

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