Noise amplitude modulation jamming signal suppression based on weighted-matching pursuit

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.

Cognitive anti-jamming receiver under phase noise in high frequency bands

This paper investigates the jamming sensing performance of the simultaneous transmit and receive based cognitive anti-jamming(SCAJ) receiver impaired by phase noise in local oscillators(LO) over fading channels. Firstly, energy detection(ED)based on the jamming to noise ratio(JNR) of the high frequency bands SCAJ receiver with phase noise under different channels is analyzed. Then, the probabilities of jamming detection and false alarm in closed-form for the SCAJ receiver are derived. Finally,the modified Bayesian Cramer-Rao bound(BCRB) of jamming sensing for the SCAJ receiver is presented. Simulation results show that the performance degradation of the SCAJ system due to phase noise is more severe than that due to the channel fading in the circumstances where the signal bandwidth(BW) is kept a constant. Moreover, the signal BW has an effect on the phase noise in LO, and the jamming detection probability of the wideband SCAJ receiver with lower phase noise outperforms that of the narrowband receiver using the same center frequency. Furthermore,an accurate phase noise estimation and compensation scheme can improve the jamming detection capability of the SCAJ receiver in high frequency bands and approach to the upper bound.

Artificial Noise Aided Polar Codes for Physical LayerSecurity

The secrecy rates of the existing practical secrecy coding methods are relative low to satisfy the security requirement of 5 G communications.We propose an artificial noise(AN) aided polar coding algorithm to improve the secrecy rate.Firstly,a secrecy coding model based on AN is presented,where the confidential bits of last transmission code block are adopted as AN to inject into the current codeword.In this way,the AN can only be eliminated from the jammed codeword by the legitimate users.Since the AN is shorter than the codeword,we then develop a suboptimal jamming positions selecting algorithm with the goal of maximizing the bit error rate of the eavesdropper.Theoretical and simulation results demonstrate that the proposed algorithm outperforms the random selection method and the method without AN.

The Response to Arbitrarily Bandlimited Gaussian Noise of the Complex Stretch Processor Using a Conventional Range-Sidelobe-Reduction Window

This paper derives a mathematical description of the complex stretch processor’s response to bandlimited Gaussian noise having arbitrary center frequency and bandwidth. The description of the complex stretch processor’s random output comprises highly accurate closed-form approximations for the probability density function and the autocorrelation function. The solution supports the complex stretch processor’s usage of any conventional range-sidelobe-reduction window. The paper then identifies two practical applications of the derived description. Digital-simulation results for the two identified applications, assuming the complex stretch processor uses the rectangular, Hamming, Blackman, or Kaiser window, verify the derivation’s correctness through favorable comparison to the theoretically predicted behavior.

A novel SINR and mutual information based radar jamming technique

The improvements of anti-jamming performance of modern radar seeker are great threats to military targets. To protect the target from detection and estimation, the novel signal-to-interference-plus-noise ratio(SINR)-based and mutual information(MI)-based jamming design techniques were proposed. To interfere with the target detection, the jamming was designed to minimize the SINR of the radar seeker. To impair the estimation performance, the mutual information between the radar echo and the random target impulse response was used as the criterion. The spectral of optimal jamming under the two criteria were achieved with the power constraints. Simulation results show the effectiveness of the jamming techniques. SINR and MI of the SINR-based jamming, the MI-based jamming as well as the predefined jamming under the same power constraints were compared. Furthermore, the probability of detection and minimum mean-square error(MMSE) were also utilized to validate the jamming performance. Under the jamming power constraint of 1 W, the relative decrease of the probability of detection using SINR-based optimal jamming is about 47%, and the relative increase of MMSE using MI-based optimal jamming is about 8%. Besides, two useful jamming design principles are concluded which can be used in limited jamming power situations.

Optimal Periodic Pulse Jamming Signal Design for QPSK Systems

The problem of optimal periodic pulse jamming design for a quadrature phase shift keying（QPSK）communication system is investigated.First a closed-form bit-error-rate（BER）of QPSK system under the jamming of pulse signal is derived.Then the asymptotic performance of the derived BER is analyzed as the signal-to-noise ratio（SNR）grows to infinity.In order to maximize the BER of the QPSK system,the optimal parameters of periodic pulse jamming signal,including the duty cycle and signal-tojamming power ratio（SJR）,are found out.Numerical results are presented to verify our analytical results and the optimality of our design.

Adaptive Threshold Clipper Combining Receiver for Fast Frequency Hopping Systems during Partial-Band Noise Jamming

Diversity combining technologies are analyzed for fast frequency-hopping spread spectrum systems during partial-band noise jamming to develop a novel combining receiver called an Adaptive Threshold Clipper Combining Receiver (ATCCR). The optimal clipping level for an ATCCR is analyzed, computed, and compared with several other diversity combining technologies. Since the ATCCR can estimate the power of the jamming and the number of jammed frequency cells to adaptively adjust the clipper's threshold, the system performance using the adaptive threshold clipper combining technique can be greatly improved.

智能反射面辅助的抗干扰安全通信系统鲁棒资源分配算法

为了解决恶意干扰攻击、窃听和不完美信道状态信息造成的通信质量降低和安全性差等问题,该文提出一种智能反射面(IRS)辅助的抗干扰安全通信系统鲁棒资源分配算法。首先,基于合法用户的最小安全速率约束、最大发射功率约束和IRS相移约束,在非法节点不完美信道状态信息、干扰器波束成形向量未知的情况下,构建了一个联合优化基站的波束成形向量、人工噪声的协方差矩阵和IRS的相移矩阵的鲁棒资源分配问题。其次,为了求解该非凸问题,利用交替优化、Cauchy-Schwarz不等式、连续凸逼近和泰勒级数展开等方法,将原问题转化为易于求解的凸优化问题。仿真结果表明,与传统算法相比所提算法能有效提高系统安全性、降低功率开销、提高抗干扰裕度,且在一定信道误差范围内能够减低约35%的保密中断概率,具有较强的鲁棒性。

基于ADBF的多通道SAR抗干扰样本选择方法

针对多通道SAR抗干扰问题,可以利用空域自由度通过自适应波束形成技术达到增强期望信号、抑制干扰的目的。在波束形成过程中,计算各阵元的最优权矢量时,需要通过选取干扰和噪声的数据样本估算干扰加噪声协方差矩阵。若选择的数据样本中掺杂目标信号,则目标信号将会被误判为干扰并被抑制。针对多通道SAR抗干扰过程中需要注意的样本选择问题,通过消除方位向频域中主杂波宽度内的目标分量,得到干扰加噪声数据样本,继而计算协方差矩阵,并进行波束形成。通过实测数据成像结果及干噪比和信噪比指标验证了提出的自适应样本选择方法的有效性。与直接样本选择方法相比,自适应样本选择方法在信噪比上提高了近8 dB,干噪比下降了近6 dB,说明了该方法有效地保留了目标信号,抑制了干扰信号。

基于载噪比同步变化的北斗欺骗检测方法

欺骗干扰已经成为北斗卫星导航系统安全性的一个严重威胁。针对北斗系统面临的欺骗干扰问题,建立二元假设检验模型。由于施加单一天线发射的欺骗干扰后,当前观测频点下各高俯仰角可见星的载噪比值会产生相同的变化趋势,所以基于此变化规律提出了一种利用K-means聚类算法进行分析的北斗卫星信号欺骗干扰检测方法,并给出了施加欺骗载噪比变化域的定义。最后通过在外场搭建实验环境,对实采数据进行了实验验证。实验结果表明,本方法对于欺骗功率优势≥6 dBm的大功率优势欺骗信号的检测概率可以达到95%以上,为提高接收机抗干扰能力提供了有益参考。

雷达、通信、干扰信号一体化检测识别技术研究

雷达信号、通信信号及其干扰信号在时域和频域都有各自的特点,当这些信号在时域、频域相互交叠时,传统的信号检测和识别算法很难将这些信号进行有效地分离,影响信号检测和参数测量。针对雷达信号、通信信号及其干扰信号在时、频域的特点,研究雷达信号、通信信号及其干扰信号在时域、频域混叠情况下的信号检测、参数测量及其信号类型识别方法。

基于某ISAR的压制干扰效果分析

逆合成孔径雷达(ISAR)作为高分辨率微波成像雷达,已经广泛应用于目标识别及精确制导。为更有效地保护目标,对于ISAR干扰的研究已成为重要的研究课题,在常见干扰方式上,对于ISAR干扰效果的评估显得尤为重要。分析常见的4种ISAR噪声压制干扰的干信比临界点,得出结论性数据,为工程应用提供有效干扰ISAR的干信比(JSR)参考门限。

基于自适应递推滤波的高压输电线路行波故障定位方法

针对传统高压输电线路测距精度差且行波法易受噪声因素影响等问题,提出了一种基于自适应递推滤波算法的高压输电线路行波故障定位方法。该方法首先经高通滤波处理后采集电流行波信号,粗定行波波头位置,选取故障前数据估计噪声的分布参数;然后基于噪声分布参数构建自适应递推滤波器对信号进行滤波;最后结合滤波后的信号与噪声参数进行比较,实现波头标定。在此基础上,结合双端测距原理实现故障点定位。仿真分析表明,所提出的方法在不同的故障条件下均可准确检测出行波信号;在弱行波信号含噪情况下,相比于小波变换,自适应递推滤波算法能有效提高输电线路故障行波定位的准确性。

无监督时频信息结合的舰船辐射噪声信号抗诱饵干扰方法

舰船辐射噪声信号是感知目标舰船的重要方式之一。诱饵信号通过模仿目标舰船辐射噪声,混淆感知系统以掩护目标舰船完成战略目标。如果可以通过对舰船辐射噪声与诱饵信号识别方式实现抗干扰,将大大提高战时敌方舰船识别效率,从而提高战术行动的效率和成功率。将抗诱饵干扰问题转化为单类分类问题,尝试采用深度学习范式给出解决方法。以此为背景,提出无监督时频信息结合的舰船辐射噪声信号抗诱饵干扰方法。构建针对舰船辐射噪声信号时域、时频域数据的对抗生成网络结构。采用对抗训练策略捕捉舰船辐射噪声信号的时域、时频域联合分布,提高模型针对舰船辐射噪声信号的表示学习能力,最终实现端到端的舰船辐射噪声信号单类分类任务。实验数据由外场实验模拟产生诱饵信号采集而来。研究结果表明:在无监督条件下的AUC值为0.84,相对于单类分类基线模型高出0.17,可以实现对舰船辐射噪声信号抗诱饵干扰。

一种融合噪声网络的深度强化学习通信干扰资源分配算法

针对传统干扰资源分配算法在处理非线性组合优化问题时需要较完备的先验信息,同时决策维度小,无法满足现代通信对抗要求的问题,该文提出一种融合噪声网络的深度强化学习通信干扰资源分配算法(FNNDRL)。借鉴噪声网络的思想,该算法设计了孪生噪声评估网络,在避免Q值高估的基础上,通过提升评估网络的随机性,保证了训练过程的探索性;基于概率熵的物理意义,设计了基于策略分布熵改进的策略网络损失函数,在最大化累计奖励的同时最大化策略分布熵,避免策略优化过程中收敛到局部最优。仿真结果表明,该算法在解决干扰资源分配问题时优于所对比的平均分配和强化学习方法,同时算法稳定性较高,对高维决策空间适应性强。

基于一维距离像的目标识别方法研究

一维距离像可为雷达对目标的识别提供重要依据,频率捷变LFMCW雷达具有距离分辨率高,抗干扰性能强等优点,本文采用该体制雷达对典型坦克目标进行基于一维距离像的目标识别方法的研究。首先对目标一维距离像进行仿真,对比不同方位角、俯仰角下的一维距离像,提出了一种基于一维距离像的连续多调频周期融合的目标识别方法,仿真结果表明该方法相较于单周期目标识别方法的识别率更高,稳定性更好。最后就噪声调幅干扰对两种目标识别方法的影响进行了仿真分析,结果表明连续多调频周期融合的目标识别方法受噪声调幅干扰的影响较小,且识别率更高。

基于低轨卫星的分布式超宽带电磁脉冲对地面接收机干扰技术

随着抗干扰技术的不断发展和进步,以阻塞式和欺骗式干扰为代表的传统干扰技术面临挑战。为此,提出了一种基于低轨卫星的分布式超宽带电磁脉冲干扰技术,相比于传统干扰机,超宽带电磁脉冲干扰是一种新型电磁攻击体制。首先,理论推导了重频超宽带电磁脉冲的功率谱;其次,对分布式干扰技术可行性进行分析,并计算了基于低轨卫星平台的分布式干扰所需的发射功率;最后,开展了针对导航接收机低噪放的超宽带电磁脉冲效应实验,并利用STK(Satellite Tool Kit)设计了中低纬度下用于搭载超宽带电磁脉冲干扰机的低轨卫星星座布局。实验结果表明,UWB电磁脉冲可以使低噪声放大器出现暂时增益压缩现象,脉宽为0.7 ns的单脉冲可以使导航信号经过低噪声放大器后被压制近400 ns,重频形式下可以实现信号的完全压制。因此,基于低轨卫星的分布式超宽带电磁脉冲干扰体系可以有效增强干扰效果,有望实现目标区域的全覆盖。

FDA-MIMO雷达噪声卷积式干扰抑制方法

基于数字射频存储器(digital radio frequency memory,DRFM)产生的噪声卷积灵巧干扰兼具压制式和欺骗式干扰的效果,严重降低了雷达系统的探测性能。为解决此问题,本文提出了一种采用频率分集阵(frequency diversity array,FDA)-多输入多输出(multiple-input-multiple-output,MIMO)雷达的噪声卷积灵巧干扰对抗方法。经由雷达发射信号和噪声信号卷积调制所得的干扰信号在距离-多普勒维与目标回波呈现不同的分布特性。据此,首先利用干扰信号在多普勒域的白噪声特性获取多普勒清晰区的干扰样本,然后在此基础上逐距离门挑选样本以获得干扰协方差矩阵,最后通过距离-角度二维匹配滤波器抑制距离不匹配的主瓣干扰信号。仿真试验验证了本文所提抗干扰方法的有效性。

基于纹理图像的强抗干扰性轴承故障诊断方法

针对传统时频分析与卷积神经网络(CNN)结合的轴承故障诊断模型抗噪性能差的问题,提出了一种能高效提取振动信号特定频段信息并具有强抗干扰性的卷积神经网络模型。根据轴承型号与运行状态自适应地将一维振动信号转换为二维卷积神经网络善于处理的纹理图像,然后将其输入首层超大卷积核的强抗干扰卷积神经网络中进行训练。抗噪和故障定位试验结果表明:改进CNN模型结构相对精简,便于训练与实际应用,在信噪比-4 dB的加噪信号上能取得97.28%的准确率,相较于该领域现有模型具有更高的故障识别率与抗噪性,而且具有较好的故障定位能力。

一种改进抽样函数自适应滤波的抗灵巧噪声干扰方法

在灵巧噪声干扰环境中,线性调频脉冲压缩体制的机载雷达对目标回波形成极好的压制性和欺骗性干扰效果,导致常规的抗干扰措施无法在时域及频域分离干扰和目标回波。针对此问题,提出了一种改进抽样函数自适应滤波的干扰抑制方法。该方法首先通过差拍处理,将信号中的二次调制项消除,使信号和干扰在频域实现解耦分离。然后采用一种改进抽样函数的变步长滤波算法,滤除解耦后的回波信号分量,最后对消解耦前后的干扰分量,通过逆差拍处理恢复目标回波信号。所提出的差拍处理方法可在频域上有效分离目标回波和灵巧噪声干扰,并通过改进的抽样函数调节步长,使解耦前后的干扰实现有效的对消。仿真结果表明,采用该方法可有效地对回波信号分量滤波,干扰分量对消效果明显,并能在信干比较低的环境下仍具有良好的鲁棒性。