伪码调相脉冲引信抗线性调频干扰分析与仿真

在对伪码调相脉冲多普勒引信工作原理和抗干扰原理分析的基础上,对占空比为4%、码长为127的伪码调相脉冲多普勒引信在LFM干扰下的相关解调输出信号和伪码序列自相关函数进行了仿真,结果发现,当信干比(SJR)为-30 dB时,该引信仍能正常工作,并且当脉冲伪码序列自相关函数的旁瓣超过门限值时,并不能引起伪码调相脉冲多普勒引信的误启动.通过仿真分析,清楚地了解了伪码调相脉冲多普勒引信在LFM干扰下的工作性能     

基于DEHT的伪码引信中多分量FM干扰抑制方法研究

在介绍离散进化变换(DET)和离散进化哈夫变换(DEHT)的基本原理基础上,详细分析了伪码引信中基于DEHT的多分量FM干扰抑制方法。接收信号首先通过DEHT估计干扰瞬时相位,并通过递归校正方法减小相位估计误差,利用估计出的干扰瞬时相位设计了一时变级联滤波器,逐个消去FM干扰。对不同干信比(ISR)情况下的干扰抑制前后的相关输出进行了仿真分析。分析结果表明,该方法能有效地去除干扰,相关输出得到显著改善。     

伪码引信瞄准式欺骗性干扰及硬件实现

该文首先介绍了伪随机码调相引信的工作原理,提出了伪随机码调相引信瞄准式欺骗性干扰机方案,并给出了各部分电路的原理及硬件实现,主要包括伪码调相信号的解调、解调后的伪码序列的识别与重构、干扰波形的调制发射等关键部件。从各部分电路的试验结果来看,本设计原理正确,方案可行。     

基于数字干扰合成的伪码调相引信干扰

为提高对伪码调相引信的干扰效果,提出了基于数字干扰合成(DJS)的数字多时延干扰信号合成方法,该方法可以极大提高干扰伪码调相引信的干扰效率。理论分析与仿真实验表明,该方法合成的干扰信号能产生不同时延的多假目标的干扰效果,兼具有欺骗干扰和压制干扰的效果,能够使干扰自动对准引信的频带并获得脉冲压缩处理增益,提高干扰能量的利用率。     

基于FRFT的伪码引信自适应LFM干扰对消方法

该文分析了LFM干扰对伪码引信相关输出的影响,当干扰强度超出伪码引信自身的抗干扰容限时,相关输出严重恶化,因此必须采取相应的抗干扰措施。考虑到LFM干扰与伪码引信有用信号间存在着强的时频耦合,提出了基于FRFT的自适应干扰对消方法。该方法首先对观察信号进行FRFT,估计干扰的特征参数,利用估计出的干扰参数构造自适应干扰对消器,将干扰去除。仿真表明,该方法能够有效滤除LFM干扰,相关输出得到显著改善,该方法对单分量和多分量干扰均有效,不受交叉项影响。     

伪码体制引信的抗噪声调频干扰性能分析

在介绍伪码体制引信的工作原理和噪声调频干扰原理的基础上,详细推导了伪码调相引信和伪码调相与PAM复合引信在噪声调频干扰环境下的总信干比增益,并仿真实现了伪码体制引信的工作过程,得出的仿真总信干比增益与理论的推导值接近。理论和仿真结果及输出的相关值证明,一般而言,伪码体制引信具有较强的抗噪声调频干扰能力。     

用投影滤波滤除伪码体制引信中的AM-FM干扰

在介绍正交投影滤波基本原理的基础上,具体分析在伪码体制引信中采用投影滤波滤除AM-FM干扰信号的方法,并对各种情况进行仿真分析,最后详细推导投影滤波后相关器的输出SNR。结果表明,用投影滤波方法既能有效地滤除伪码体制引信中的FM干扰,也能很好地滤除AM-FM干扰,从而有效提高相关器的输出SNR,而且不会导致接收端所期望的伪码的失真,但干扰参数的估计误差对滤除AM-FM干扰的影响较大。     

基于自适应窗长WD分析的伪码调相-载波调频复合引信信号的参数提取研究

该文研究了自适应窗长时频分析的理论及其实现方法,利用该方法对伪码体制复合引信信号进行脉冲内特征分析。这些信号具体包括伪码调相信号、伪码调相与正弦调频复合信号、伪码调相与线性调频复合信号。仿真结果表明,在信噪比为10dB时,利用自适应窗长时频分析技术,不但可以提取载频调制的特征信息,而且能够有效提取相位突变位置的特征信息。     

联合时频重排和双正交傅里叶变换对抗频谱弥散干扰

频谱弥散（SMSP）干扰由多个LFM子信号时域拼接而成，利用信号处理工具重构干扰信号，需要进行多次滤波。针对该问题，分析了SMSP干扰时频特征，在此基础上，提出联合时频重排和双正交傅里叶变换SMSP干扰抑制算法。首先，对回波时频重排矩阵进行Radon变换，估计干扰子信号个数。其次，根据估计的子信号个数设计参考信号，将回波中的SMSP干扰调制成一个LFM信号。然后，对调制后回波进行BFT峰值滤波处理，解调重构干扰信号。最后，将回波减去重构信号实现干扰抑制。仿真结果表明，所提算法无需估计全部干扰参数，仅需一次峰值滤波解调处理即可准确重构干扰信号，对消后回波中的SMSP干扰得到有效抑制。      

对GPS接收机的一种新宽带压制干扰样式分析

针对单频连续波干扰极易通过频域滤波加以抑制,而宽带连续阻塞式干扰又存在干扰效率低下的问题,提出脉冲连续波这种新的宽带梳状拦阻式干扰样式。根据C/A码、P(Y)码和M码信号功率谱特点分别设置脉冲连续波的干扰频率覆盖范围。以码跟踪误差作为干扰效果评估指标,对不同干扰环境下采用窄带非相干延迟锁定环的GPS接收机码跟踪性能进行仿真分析。仿真结果表明:脉冲连续波干扰对不同伪随机噪声码(PRN)编号和副载波调制相位下的C/A码和M码信号影响是不同的,在相同干信比(JSR)条件下,脉冲连续波的干扰效果要优于宽带高斯噪声和匹配谱干扰。     

一种空-频联合最优滤波的被动宽带检测方法

常规宽带能量检测在多目标、强干扰环境下输出信噪比(SNR)降低,检测性能大幅度下降。针对此问题,该文提出一种将子阵导向最小方差(STMV)宽带空域自适应波束形成与频域Eckart滤波结合的空-频联合最优滤波宽带检测方法。该方法首先通过子阵导向最小方差波束形成进行空间自适应处理,利用自适应波束形成的干扰抑制能力在空域实现最优滤波;然后通过最大似然估计实时估计信号和噪声的功率谱,构造Eckart滤波对自适应波束形成的输出分配不同权重进行加权滤波,从而实现频域信噪比最大化。所提方法通过空-频联合最优滤波,降低空域旁瓣干扰和频带内噪声的影响,使得输出信噪比最大,从而有效地改善目标宽带检测能力,提高被动声呐的宽带检测性能。仿真和试验数据处理结果验证了该方法的有效性。     

Impact of phase noise in weakly coherent systems: a new andaccurate approach

Coherent optical systems for future broadband local loops may use lasers with significant phase noise, manifest as broad linewidths. This phase noise can be accommodated if the receiver is correctly designed, i.e. if nonsynchronous (envelope or square-law) IF demodulation is used and sufficient IF bandwidth is provided. It is difficult to analyze the performance of a coherent optical receiver when the signals are corrupted by phase noise. The central theoretical problem arising from filtering a signal with phase noise is defined in a particular form which permits the derivation of the forward or Fokker-Planck partial differential equation for probability density of the output voltage of the receiver. The results are used to discuss the IF bandwidth required for optical heterodyne receivers for amplitude-shift-keying (ASK) signals     

Phase error correcting vector modulator for personal communications network (PCN) transceivers

A technique is reported for correcting phase errors in vector modulators for application in PCN (personal communication network) transceivers. The technique uses an AM demodulation process to extract the phase error from the output signal, and uses the capability of direct digital frequency synthesisers to predistort the phase of the inphase and quadrature components separately. The phase predistortion method can achieve accuracies of less than 0.05 degrees phase error, which can be further improved by increasing the number of bits in the synthesis.<>     

Partially adaptive beamforming for correlated interferencerejection

Conventional linearly constrained adaptive beamformers often suffer from severe signal cancellation in the presence of interferers correlated with the signal. We propose a partially adaptive beamforming technique for correlated interference rejection in broadband signal environments. The beamformer output mean squared error is decomposed into an interference mean squared error term and an additional signal cancellation term that is due to the presence of correlated interference. Both mean squared errors depend on the adaptation space. The partially adaptive beamforming technique proposed here chooses an adaptation space which results in little signal cancellation while maintaining satisfactory interference cancellation. It is shown that, for a given interference scenario, a partially adaptive beamformer can be designed such that maximum interference cancellation is achieved without any signal cancellation. In practice, an approximate design procedure is provided to accommodate a set of likely interference scenarios. Analysis of the feasibility of this approach is presented. The effectiveness of the technique is demonstrated through examples     

通信对抗中的自适应滤波技术

自适应滤波是在维纳滤波和Kalman滤波等线性滤波基础上发展起来的一种最佳滤波方法,具有较强的适应性和较优的滤波性能。这里将自适应滤波技术应用于电子对抗领域,利用自适应滤波原理计算出一个数字滤波器,对各信道的增益失配与相移失配进行精确的通道均衡补偿;利用自适应滤波方法设计具有特定频率响应的FIR滤波器,可实现时域宽带波束形成技术,并实现了基于自适应滤波的同平台干扰抵消技术。     

极化敏感阵列斜投影滤波性能分析

该文研究了极化敏感阵列采用斜投影滤波和正交投影滤波的输出信干噪比(SINR)特性。推导获得了斜投影滤波与正交投影滤波在理想情况和存在阵列误差时的输出SINR 计算式:理想情况下输出SINR 是信噪比(SNR)、目标与干扰的空域和极化域匹配系数的函数;存在阵列误差情况时输出SINR 受信噪比,干噪比(INR)、目标与干扰的空域-极化域匹配系数及误差扰动量共同影响。分析表明,相比正交投影滤波而言,斜投影滤波的输出SINR没有改善,也不能提高误差稳健性,它们均低于最优输出SINR;正交投影与斜投影输出SINR 相同的成因并不一样,正交投影滤波改变了目标的幅相特性,滤波后目标有损失;斜投影滤波改变了输出噪声的空域-极化域特性,放大了输出噪声的功率。最后通过仿真实验验证了理论分析的正确性。      

Optical pulse sequence transmission through single-mode fibers:interference signal analysis

The transmission of a pulse sequence through a single-mode fiber is considered under first- and second-order dispersion. An expression is given for the output power signal envelope in terms of the Fourier transform of a spectral function. The output envelope is composed of two terms: a linear one which is a distorted replica of the information sequence, and a nonlinear interference term. The latter is expressed in a more meaningful way and analyzed. The results allow a characterization and a classification of the interference pulses in terms of physically intuitive parameters     

Design of robust envelope-constrained filter with orthonormal bases

In the continuous-time envelope-constrained (EC) filtering problem using an orthonormal filter structure, the aim is to synthesize an orthonormal filter such that the noise enhancement is minimized while the noiseless output response of the filter with respect to a specified input signal stays within the upper and lower bounds of the envelope. The noiseless output response of the optimum filter to the prescribed input signal touches the output boundaries at some points. Consequently, any disturbance in the prescribed input signal or error in the implementation of the optimal filter will result in the output constraints being violated. In this paper, we review a semi-infinite envelope-constrained filtering problem in which the constraint robustness margin of the filter is maximized, subject to a specified allowable increase in the optimal noisy power gain. Using a smoothing technique, it is shown that the solution of the optimization problem can be obtained by solving a sequence of strictly convex optimization problems with integral cost. An efficient optimization algorithm is developed based on a combination of the golden section search method and the quasi-Newton method