This paper focuses on the jamming problem of bistatic synthetic aperture radar (BiSAR), and a jamming method against BiSAR based on modulation theory is proposed. The proposed jamming method modulates the BiSAR signal...This paper focuses on the jamming problem of bistatic synthetic aperture radar (BiSAR), and a jamming method against BiSAR based on modulation theory is proposed. The proposed jamming method modulates the BiSAR signal with the cosinusoidal phase to generate multi-false targets in range, and further rotates the jammer to generate multi-false targets in azimuth. The range multi-false targets and azimuth multi-false targets form the two-dimensional cover jamming or deception jamming, which can protect the important targets efficiently. The number of false targets, the interval of false targets, and the jamming square can be adjusted flexibly by setting different range jamming parameters and azimuth jamming parameters. The jamming performance and the choosing criteria of jamming parameters are also discussed. Finally, the simulated data verify the effectiveness of the jamming method.展开更多
To suppress noise amplitude modulation jamming in a single-antenna radar system, a new method based on weighted-matching pursuit (WMP) algorithm is proposed, which can achieve underdetermined blind sources separatio...To suppress noise amplitude modulation jamming in a single-antenna radar system, a new method based on weighted-matching pursuit (WMP) algorithm is proposed, which can achieve underdetermined blind sources separation of the jamming and the target echo from the jammed mixture in the single channel of the receiver. Firstly, the presented method utilizes a prior information about the differences between the jamming component and the radar transmitted signal to construct two signal-adapted sub-dictionaries and to determine the weights. Then the WMP algorithm is applied to remove the jamming component from the mixture. Experimental results verify the validity of the presented method. By comparison of the pulse compression performance, the simulation results shows that the presented method is superior to the method of frequency domain cancellation (FDC) when the jamming-to-signal ratio (JSR) is lower than 15 dB.展开更多
It is potentially useful to perform deception or cover jamming using the rotating angular reflectors since they can form deception echoes along range and azimuth. Inspired by the cohe- rent jamming and micro-motion mo...It is potentially useful to perform deception or cover jamming using the rotating angular reflectors since they can form deception echoes along range and azimuth. Inspired by the cohe- rent jamming and micro-motion modulation, a novel active method is proposed for inverse synthetic aperture radar (ISAR). Radar pulses are sampled and frequency-modulated along azimuth by si- nusoidal signal, and then the jamming signals are retransmitted to the radar and the jamming images are induced after ISAR imaging. Therein, the jamming principle, key parameters and the jamming effect are discussed. The simulated data verify the effectiveness of the jamming method.展开更多
In electromagnetic countermeasures circumstances,synthetic aperture radar(SAR)imagery usually suffers from severe quality degradation from modulated interrupt sampling repeater jamming(MISRJ),which usually owes consid...In electromagnetic countermeasures circumstances,synthetic aperture radar(SAR)imagery usually suffers from severe quality degradation from modulated interrupt sampling repeater jamming(MISRJ),which usually owes considerable coherence with the SAR transmission waveform together with periodical modulation patterns.This paper develops an MISRJ suppression algorithm for SAR imagery with online dictionary learning.In the algorithm,the jamming modulation temporal properties are exploited with extracting and sorting MISRJ slices using fast-time autocorrelation.Online dictionary learning is followed to separate real signals from jamming slices.Under the learned representation,time-varying MISRJs are suppressed effectively.Both simulated and real-measured SAR data are also used to confirm advantages in suppressing time-varying MISRJs over traditional methods.展开更多
Stepped frequency chirp signal obtains high-resolution radar images by synthesizing multiple narrowband chirp pulses.It has been one of the most commonly used wideband radar waveforms due to its lower demand for radar...Stepped frequency chirp signal obtains high-resolution radar images by synthesizing multiple narrowband chirp pulses.It has been one of the most commonly used wideband radar waveforms due to its lower demand for radar instant bandwidth.In this paper,we propose a radar jamming method using two-dimensional nonperiodic phase modulation against stepped frequency chirp signal imaging radar.Using the unique property of nonperiodic phase modulation,the proposed method can generate high-level sidelobes that perform as a special blanket jamming along both the range and azimuth directions and make the target unrecognizable.Then,the influence of different modulation parameters,such as the code width and duty ratio,are further discussed.Based on this,the corresponding parameter design principles are presented.Finally,the validity of the proposed method is demonstrated by the Yake-42 plane data simulation and measured unmanned aerial vehicle data experiment.展开更多
The inherent mathematic principle of active jamming against the wideband linear frequency modulated(LFM) radar is investigated. According to different generation strategies, the active jamming methods are reclassifi...The inherent mathematic principle of active jamming against the wideband linear frequency modulated(LFM) radar is investigated. According to different generation strategies, the active jamming methods are reclassified into three groups, i.e.,non-coherent jamming(NCJ), convolution jamming(CJ) and multiplying jamming(MJ). Based on the classification, the mathematic principles of different active jamming groups are put forward, which describe the relationships between the modulated signals and the jamming results. The advantages and disadvantages of different groups are further analyzed, which provides a new perspective for the study of jamming/anti-jamming methods and a potential for engineers to integrate similar jamming methods into one jammer platform. The analyses and simulation results of some typical active jamming methods prove the validity of the proposed mathematics principle.展开更多
对多雷达干扰效果评估的难点在于分析干扰机对非目标雷达的影响。针对干扰机转发一部线性调频(linear frequency modulation,LFM)雷达的信号无意干扰另一部LFM雷达时的检测概率估计问题,首先计算了被干扰雷达对干扰信号在空域、频域和...对多雷达干扰效果评估的难点在于分析干扰机对非目标雷达的影响。针对干扰机转发一部线性调频(linear frequency modulation,LFM)雷达的信号无意干扰另一部LFM雷达时的检测概率估计问题,首先计算了被干扰雷达对干扰信号在空域、频域和时域上的接收增益;其次将干扰信号在判决单元中的统计特性建模为非中心卡方分布,并给出了检测概率和虚警概率的计算方法。仿真结果表明,在一部干扰机的无意干扰下,估计的检测概率可作为被干扰雷达检测概率的上限;为达到同样的干扰效果,转发非目标雷达的信号实施干扰,比转发目标雷达的信号进行干扰所需的干扰功率更少。展开更多
A novel algorithm is proposed to resolve the defects in the traditional linear frequency modulation(LFM)jamming suppression algorithm in the fractional Fourier transform(FRFT)domain.The traditional LFM jamming suppres...A novel algorithm is proposed to resolve the defects in the traditional linear frequency modulation(LFM)jamming suppression algorithm in the fractional Fourier transform(FRFT)domain.The traditional LFM jamming suppression algorithm in the FRFT domain has some defects.For example,the exact threshold is difficult to set and both the signal-to-noise ratio(SNR)loss and spectrum leakage are serious in strong jamming-to-signal ratio(JSR)situations.Windowing,overlapping and inverse windowing techniques are used in the FRFT domain to reduce the spectrum leakage and the SNR loss.Under the condition that only the direct sequence spread spectrum(DSSS)signal and white Gaussian noise are present,the amplitude of the received signal after FRFT is assumed to be Rayleigh distributed.Based on the distribution characteristic,hypothesis testing is used to suppress the jamming spectrum using the algorithm.Simulation results show that the performance of proposed algorithm is better than that of the conventional algorithms,especially in a strong jamming and multi component LFM jamming environment.展开更多
To improve the signal detection performance of binary-sequence frequency hopping communication when the complementary channel is jammed, a binary-sequence frequency hopping communication system based on pseudo-random ...To improve the signal detection performance of binary-sequence frequency hopping communication when the complementary channel is jammed, a binary-sequence frequency hopping communication system based on pseudo-random liner frequency modulation (LFM) is proposed. The transmitting end uses the chirp signal to carry out the in-band spread spectrum of the binary-sequence frequency hopping signal, and then sends it out through the radio frequency front end. At the receiving end, the received signal is dehopped and processed by fractional Fourier transform. The source information is obtained by sampling decision. Firstly, a binary-sequence frequency hopping system model based on pseudo-random LFM is constructed. Secondly, the bit error rate expression of anti-partial band jamming and follower jamming under the Rice channel is derived. The results show that this method has at least 5 dB performance gain than binary sequence frequency hopping for different parameter settings under partial band jamming and follower jamming, and the anti-jamming performance is significantly better than the conventional frequency hopping communication.展开更多
针对步进线性调频信号(stepped frequency-linear frequency modulation,SF-LFM)体制雷达对抗问题,提出了一种基于子脉冲间歇采样的干扰方法。通过对截获SF-LFM信号的子脉冲进行交替采样与转发,在雷达成像处理后可形成沿距离向延拓的逼...针对步进线性调频信号(stepped frequency-linear frequency modulation,SF-LFM)体制雷达对抗问题,提出了一种基于子脉冲间歇采样的干扰方法。通过对截获SF-LFM信号的子脉冲进行交替采样与转发,在雷达成像处理后可形成沿距离向延拓的逼真假目标。在此基础上对其干扰特性与参数设计问题进行了讨论,并分别通过一维理想散射点仿真与某型飞机二维成像数据仿真实验验证了所提方法有效性。展开更多
角反射器是一种宽角域的常见无源干扰设备,常被用于保护关键目标.但传统金属角反射器特性固定,需借助新型电磁材料实现角反射器的特性优化.有源频率选择表面(adaptive frequency selective surface,AFSS)是在单元间加载一系列可变有源...角反射器是一种宽角域的常见无源干扰设备,常被用于保护关键目标.但传统金属角反射器特性固定,需借助新型电磁材料实现角反射器的特性优化.有源频率选择表面(adaptive frequency selective surface,AFSS)是在单元间加载一系列可变有源器件而构成的具有可调电磁特性的新型结构.为拓展角反射器的适用范围、分析电磁材料角反射器的散射特性以更好地保护关键目标,本文设计了一种基于单面AFSS的电控角反射器,并仿真计算分析了该电控角反射器的散射特性.仿真结果表明设计的电控角反射器的散射特性可灵活调控,即不同偏置电流下AFSS单元可对入射电磁波能量产生不同反射效果;同时验证了该电磁调控角反射器的宽角域特性,其调控角域在方位向、俯仰向均大于60°,实现了基于无源散射体的宽角域实时调控效果.相较于传统角反射器和平面电磁材料,所设计电控角反射器兼具实时调控性和宽角域特性,拓展了角反射器的应用场景和适用范围.展开更多
基金supported by the National Defense Pre-research Program during the 13th Five-Year Plan(30603050303 301020302)
文摘This paper focuses on the jamming problem of bistatic synthetic aperture radar (BiSAR), and a jamming method against BiSAR based on modulation theory is proposed. The proposed jamming method modulates the BiSAR signal with the cosinusoidal phase to generate multi-false targets in range, and further rotates the jammer to generate multi-false targets in azimuth. The range multi-false targets and azimuth multi-false targets form the two-dimensional cover jamming or deception jamming, which can protect the important targets efficiently. The number of false targets, the interval of false targets, and the jamming square can be adjusted flexibly by setting different range jamming parameters and azimuth jamming parameters. The jamming performance and the choosing criteria of jamming parameters are also discussed. Finally, the simulated data verify the effectiveness of the jamming method.
文摘To suppress noise amplitude modulation jamming in a single-antenna radar system, a new method based on weighted-matching pursuit (WMP) algorithm is proposed, which can achieve underdetermined blind sources separation of the jamming and the target echo from the jammed mixture in the single channel of the receiver. Firstly, the presented method utilizes a prior information about the differences between the jamming component and the radar transmitted signal to construct two signal-adapted sub-dictionaries and to determine the weights. Then the WMP algorithm is applied to remove the jamming component from the mixture. Experimental results verify the validity of the presented method. By comparison of the pulse compression performance, the simulation results shows that the presented method is superior to the method of frequency domain cancellation (FDC) when the jamming-to-signal ratio (JSR) is lower than 15 dB.
基金supported by the Fundamental Research Funds for the Central Universities(K50511020024)
文摘It is potentially useful to perform deception or cover jamming using the rotating angular reflectors since they can form deception echoes along range and azimuth. Inspired by the cohe- rent jamming and micro-motion modulation, a novel active method is proposed for inverse synthetic aperture radar (ISAR). Radar pulses are sampled and frequency-modulated along azimuth by si- nusoidal signal, and then the jamming signals are retransmitted to the radar and the jamming images are induced after ISAR imaging. Therein, the jamming principle, key parameters and the jamming effect are discussed. The simulated data verify the effectiveness of the jamming method.
基金supported by the National Natural Science Foundation of China(61771372,61771367,62101494)the National Outstanding Youth Science Fund Project(61525105)+1 种基金Shenzhen Science and Technology Program(KQTD20190929172704911)the Aeronautic al Science Foundation of China(2019200M1001)。
文摘In electromagnetic countermeasures circumstances,synthetic aperture radar(SAR)imagery usually suffers from severe quality degradation from modulated interrupt sampling repeater jamming(MISRJ),which usually owes considerable coherence with the SAR transmission waveform together with periodical modulation patterns.This paper develops an MISRJ suppression algorithm for SAR imagery with online dictionary learning.In the algorithm,the jamming modulation temporal properties are exploited with extracting and sorting MISRJ slices using fast-time autocorrelation.Online dictionary learning is followed to separate real signals from jamming slices.Under the learned representation,time-varying MISRJs are suppressed effectively.Both simulated and real-measured SAR data are also used to confirm advantages in suppressing time-varying MISRJs over traditional methods.
基金Project supported by the Natural Science Foundation of Hunan Province,China(No.2022JJ40561)the Scientific Research Program of National University of Defense Technology,China(No.ZK22-46)the National Natural Science Foundation of China(Nos.61890542,62001481,and 62071475)。
文摘Stepped frequency chirp signal obtains high-resolution radar images by synthesizing multiple narrowband chirp pulses.It has been one of the most commonly used wideband radar waveforms due to its lower demand for radar instant bandwidth.In this paper,we propose a radar jamming method using two-dimensional nonperiodic phase modulation against stepped frequency chirp signal imaging radar.Using the unique property of nonperiodic phase modulation,the proposed method can generate high-level sidelobes that perform as a special blanket jamming along both the range and azimuth directions and make the target unrecognizable.Then,the influence of different modulation parameters,such as the code width and duty ratio,are further discussed.Based on this,the corresponding parameter design principles are presented.Finally,the validity of the proposed method is demonstrated by the Yake-42 plane data simulation and measured unmanned aerial vehicle data experiment.
基金supported by the National Natural Science Foundation of China(61271442)
文摘The inherent mathematic principle of active jamming against the wideband linear frequency modulated(LFM) radar is investigated. According to different generation strategies, the active jamming methods are reclassified into three groups, i.e.,non-coherent jamming(NCJ), convolution jamming(CJ) and multiplying jamming(MJ). Based on the classification, the mathematic principles of different active jamming groups are put forward, which describe the relationships between the modulated signals and the jamming results. The advantages and disadvantages of different groups are further analyzed, which provides a new perspective for the study of jamming/anti-jamming methods and a potential for engineers to integrate similar jamming methods into one jammer platform. The analyses and simulation results of some typical active jamming methods prove the validity of the proposed mathematics principle.
文摘对多雷达干扰效果评估的难点在于分析干扰机对非目标雷达的影响。针对干扰机转发一部线性调频(linear frequency modulation,LFM)雷达的信号无意干扰另一部LFM雷达时的检测概率估计问题,首先计算了被干扰雷达对干扰信号在空域、频域和时域上的接收增益;其次将干扰信号在判决单元中的统计特性建模为非中心卡方分布,并给出了检测概率和虚警概率的计算方法。仿真结果表明,在一部干扰机的无意干扰下,估计的检测概率可作为被干扰雷达检测概率的上限;为达到同样的干扰效果,转发非目标雷达的信号实施干扰,比转发目标雷达的信号进行干扰所需的干扰功率更少。
基金National Natural Science Foundation of China(61175059)the Natural Science Foundation of Hebei Province(F2011205023)。
文摘A novel algorithm is proposed to resolve the defects in the traditional linear frequency modulation(LFM)jamming suppression algorithm in the fractional Fourier transform(FRFT)domain.The traditional LFM jamming suppression algorithm in the FRFT domain has some defects.For example,the exact threshold is difficult to set and both the signal-to-noise ratio(SNR)loss and spectrum leakage are serious in strong jamming-to-signal ratio(JSR)situations.Windowing,overlapping and inverse windowing techniques are used in the FRFT domain to reduce the spectrum leakage and the SNR loss.Under the condition that only the direct sequence spread spectrum(DSSS)signal and white Gaussian noise are present,the amplitude of the received signal after FRFT is assumed to be Rayleigh distributed.Based on the distribution characteristic,hypothesis testing is used to suppress the jamming spectrum using the algorithm.Simulation results show that the performance of proposed algorithm is better than that of the conventional algorithms,especially in a strong jamming and multi component LFM jamming environment.
基金the National Natural Science Foundation of China (Nos. 61531009 and 61471108)the National Major Project Foundation of China (No. 2016ZX03001009)the Natural Science Foundation of Hebei Province (No. F2017506006)。
文摘To improve the signal detection performance of binary-sequence frequency hopping communication when the complementary channel is jammed, a binary-sequence frequency hopping communication system based on pseudo-random liner frequency modulation (LFM) is proposed. The transmitting end uses the chirp signal to carry out the in-band spread spectrum of the binary-sequence frequency hopping signal, and then sends it out through the radio frequency front end. At the receiving end, the received signal is dehopped and processed by fractional Fourier transform. The source information is obtained by sampling decision. Firstly, a binary-sequence frequency hopping system model based on pseudo-random LFM is constructed. Secondly, the bit error rate expression of anti-partial band jamming and follower jamming under the Rice channel is derived. The results show that this method has at least 5 dB performance gain than binary sequence frequency hopping for different parameter settings under partial band jamming and follower jamming, and the anti-jamming performance is significantly better than the conventional frequency hopping communication.
文摘针对步进线性调频信号(stepped frequency-linear frequency modulation,SF-LFM)体制雷达对抗问题,提出了一种基于子脉冲间歇采样的干扰方法。通过对截获SF-LFM信号的子脉冲进行交替采样与转发,在雷达成像处理后可形成沿距离向延拓的逼真假目标。在此基础上对其干扰特性与参数设计问题进行了讨论,并分别通过一维理想散射点仿真与某型飞机二维成像数据仿真实验验证了所提方法有效性。
文摘角反射器是一种宽角域的常见无源干扰设备,常被用于保护关键目标.但传统金属角反射器特性固定,需借助新型电磁材料实现角反射器的特性优化.有源频率选择表面(adaptive frequency selective surface,AFSS)是在单元间加载一系列可变有源器件而构成的具有可调电磁特性的新型结构.为拓展角反射器的适用范围、分析电磁材料角反射器的散射特性以更好地保护关键目标,本文设计了一种基于单面AFSS的电控角反射器,并仿真计算分析了该电控角反射器的散射特性.仿真结果表明设计的电控角反射器的散射特性可灵活调控,即不同偏置电流下AFSS单元可对入射电磁波能量产生不同反射效果;同时验证了该电磁调控角反射器的宽角域特性,其调控角域在方位向、俯仰向均大于60°,实现了基于无源散射体的宽角域实时调控效果.相较于传统角反射器和平面电磁材料,所设计电控角反射器兼具实时调控性和宽角域特性,拓展了角反射器的应用场景和适用范围.