干扰对消系统的非零带宽性能与延时匹配

分析了干扰信号非零带宽下,实际自适应干扰对消系统的频域特性和时域特性。非零带宽信号使系统时变,当带宽远小于中心频率时,系统可近似为自适应梳状滤波器。系统的平均收敛速度与总参考信号幅值成正比,干扰对消比随信号带宽的增大而减小。对耦合延时匹配进行了理论和仿真分析,分析表明,耦合延时匹配可以显著提高宽带干扰对消比和对消带宽,延时匹配越精确,对消效果越好。     

一种改进的自适应干扰对消技术研究及在电磁辐射测量中的应用

提出了一种适合于处理非平稳随机信号的改进自适应干扰对消算法.首先利用经验模态分解的分频特性将多频复杂信号分解到不同的固有模态函数中,再利用改进的最小均方自适应算法进行干扰对消.计算机仿真以及试验结果证明,该方法有效地滤除了含噪电磁信号中的电磁噪声干扰,提高了电磁辐射测鼍的速度和精度,具有重要的工程应用价值.     

自适应旁瓣对消在雷达中的应用

自适应旁瓣对消(ASLC)是雷达抗有源干扰的有效方法.它采用空间滤波技术,通过辅助接收通道在干扰方向形成波束图的零点,实现对干扰信号的抑制.本文介绍了自适应旁瓣对消的原理,然后给出了基于DSP的ASLC实现方案,分析了自适应旁瓣对消的性能.同传统的对消系统相比,该系统具有更好的抗干扰性能.     

雷达中的自适应极化滤波技术

在雷达检测接收机之输入端的目标信号的平均功率与不需要的信号的平均功率之比,通过采用某些基于利用回波极化状态的自适应信号处理方法,而有可能大大提高。不需要的雷达回波的抑制通常是通过一个双极化雷达信号的矢量处理而获得的,这等效于使接收天线的状态自适应于不需要的环境状况。在本文中,在讨论某些关于部分极化的不需要的雷达回波的自适应对消概念之后,分析一种新的非线性自适应极化对消器的工作与性能。这种对消器在存在阻塞干扰或降雨杂波情况下可用于改善信号一干扰比。在文末,展示了某些与实验双极化雷达数据有关的结果。     

参考信号耦合有用信号对干扰对消系统的影响及其抑制

分析了参考信号耦合有用信号时,实际自适应干扰对消系统的时域特性。分析表明,参考信号含有用信号导致系统时变,改变系统的最佳权值,使系统的干扰对消效果下降,并对有用信号的接收产生影响。根据实际共平台通信系统的收发耦合特性,从时域角度分析得到系统干扰对消比和有用对消比的计算表达式,并得到干扰对消比和有用对消比随相对时延相位变化的规律。提出一种时延匹配方法,通过匹配参考信号提取点至正交功分器输出与接收天线至合成信号注入点间的时延,可以有效抑制参考信号耦合有用信号导致干扰对消效果下降的问题。仿真结果表明,所提出的时延匹配方法能消除有用信号对干扰对消比的影响,还能提高干扰对消效果。     

基于改进变步长自适应滤波的密集假目标干扰抑制方法

提出了一种基于改进变步长自适应滤波的密集假目标干扰抑制方法。该方法首先采用stretch去斜处理,消去信号的二次项,并在频域上分离目标回波与干扰,从而得到频率不同的信号分量;然后用基于类箕舌线函数的变步长自适应滤波方法,对stretch处理后的回波信号滤波;最后对消密集假目标干扰,将对消后的信号作逆stretch处理恢复目标回波。所提出的类箕舌线函数调节自适应滤波方法中的步长,能有效地抑制距离目标回波较近的假目标干扰。仿真结果表明,改进变步长自适应滤波方法在目标回波与干扰时延差较小时,也可有效地对回波信号滤波,干扰对消效果明显;与基于定步长的滤波方法相比,所提方法在信干比较低的环境下仍具有良好的鲁棒性,并能有效抑制密集假目标干扰。     

对自适应旁瓣对消系统的闪烁干扰方案研究

现代雷达普遍采用旁瓣对消技术抗有源干扰,该技术大大降低了从雷达天线旁瓣进入的干扰信号功率,使得从雷达天线旁瓣进入的有害干扰信号不至于严重妨碍雷达工作。文中分析了雷达开环自适应旁瓣对消系统的工作原理,提出了采用对开环自适应旁瓣对消系统进行闪烁干扰的理论依据及实施方法,并对闪烁干扰的干扰效果进行仿真分析,结果证实了闪烁干扰的可行性,为干扰自适应旁瓣对消系统提出了可行的干扰方案。     

宽带泄漏信号自适应对消器的性能

自适应对消器可以有效地消除雷达发射机宽带泄漏信号对雷达系统本身的影响。本文依据环路模型建立了描述自适应对消器工作过程的随机微分方程,求得了随机微分方程的瞬态解及其统计特性。最后导出了衡量对消器性能的干扰对消比的理论公式。     

基于自适应旁瓣对消的测角研究

自适应波束形成(ADBF)和自适应旁瓣对消算法都能够很好地抑制旁瓣干扰,但是由于干扰协方差矩阵的影响,ADBF在抑制干扰同时给和、差单脉冲测角带来误差.文中针对自适应旁瓣对消算法,系统研究了其在和、差单脉冲测角中的应用,着重分析了辅助天线中的目标信号对测角性能的影响.理论分析和仿真结果表明,辅助天线中的目标信号对测角的影响主要存在于辅助天线的增益大于差波束增益的角域,而在其他角域,影响很小.     

雷达自适应旁瓣干扰对消系统的改进

研究了传统旁瓣自适应干扰对消系统,在强近地杂波接收时,由于近地杂波强度太大而影响了对消系统的正常工作,并最终影响到回波有用信号提取这一问题,由此提出了一种基于收敛权值存储的自适应对消系统,并给出了详细实现方案。经理论仿真和实际设备装调,结果证明利用该方案的旁瓣自适应干扰对消系统能有效解决近地接收时强地杂波带来的影响。     

New aspects to event-synchronous cancellation of ECG interference: an application of the method in diaphragmatic EMG signals

An "event-synchronous interference canceller" (ESC) for cancellation of electrocardiographic (ECG) interference in diaphragmatic electromyographic (EMGdi) signals is addressed in this paper. ESC pursues the concept of the "event synchronous adaptive interference canceller" (ESAIC), which was proposed in [1] as a specific application of the well known "adaptive noise canceller" (ANC) paradigm, but ESC uses a simple adaptive gain control (AGC) instead of the complex adaptive filter of the ANC. The proposed ESC method is evaluated using both computer simulations and real EMGdi data, and its efficiency in interference cancellation is compared to that of ESAIC. Of particular interest is the result that the ESC can replace the ESAIC providing better performance as well as a considerable reduction of computational costs.     

An adaptive canceller of cochannel interference for spread-spectrummultiple-access communication networks in a power line

The authors propose and investigate an adaptive canceller of intersymbol and cochannel interference due to channel distortion and cross-correlation among pseudonoise sequences assigned to individual users of a DS-SSMA (direct-sequence spread-spectrum multiple-access) system. In order to implement a local area network (LAN) by using a power line installed in a building wall as a transmission channel, the authors have investigated utilization of DS-SSMA which has advantages such as robustness against narrow-band interference and noise and realization of asynchronous code division multiple access. In a power line, however, restriction of transmission bandwidth for communications makes it difficult to suppress cochannel interference and the channel is also time-varying due to fluctuation of loads. Since the proposed canceller adaptively eliminates cochannel interference as well as intersymbol interference, it can facilitate synchronization and increase the number of the simultaneously accessing users on a power line with restricted processing gain. The error probability in the output of the canceller is theoretically calculated for the steady-state case by using a Markov model. Computer simulations illustrate stable convergence properties of the canceller     

基于小波神经网络的非线性噪声对消

利用小波神经网络作为噪声对消滤波器,实现了参考噪声与干扰噪声呈非线性相关条件下的噪声对消。在参考噪声与干扰噪声非线性相关时,传统的横向滤波器效果不理想,利用小波神经网络的非线性特性,可更好的解决非线性噪声条件下的噪声对消问题。计算机仿真结果证明,小波神经网络噪声对消在非线性噪声条件可有效提高信噪比增益。     

噪声对消在信号处理系统中的应用

论述基于LMS算法的自适应滤波器噪声对消的工作原理,以及基于AR模型的信号分析方法。在这两种方法相结合的情况下,能有效去除信号的噪声。对含有瞬态干扰的微弱信号,用AR模型法估计出噪声的系数并预测噪声波形,通过自适应滤波器噪声对消原理进行滤波,最后在Matlab环境下进行仿真试验,结果表明该方法具有较好的去噪效果。     

新的自适应盲噪声抑制在语音处理中的应用

传统的自适应滤波去噪的系统中需要一个参考信号,实际中一般事先并不知道噪声的特性,而且噪声也是时变的。因此提出一种新的基于盲噪声抑制方法,可降噪并跟踪噪声特性的变化,随时调节滤波器的系数,比传统的自适应噪声控制具有优势。     

一种改进的自适应回波抵消器的设计与实现

回波是广泛存在于各种通信信道中的噪声干扰.传统的回波抵消器只能滤除缓变的、线性的回波干扰,对一些非线性且较复杂的信道产生的回波,滤波效果并不理想.本文通过比较融合两种经典的自适应算法,LMS算法和RLS算法各自的优点,提出了一种改进的自适应回波抵消器的结构,该回波抵消器已通过MATLAB仿真实现.从仿真的结果来看,该回波抵消器在对信道的兼容性,以及鲁棒性均优于传统回波抵消器.     

面向二元麦克风小阵列改进的广义旁瓣抵消器语音增强算法

二元麦克风小阵列在手机、助听器等受空间、成本以及运算能力限制的设备中被广泛研究用以提高目标语音质量。二元麦克风小阵列中语音增强算法主要包括波束形成方法以及相干性滤波器方法。波束形成方法的思想是利用目标声源相对阵列的位置关系获取相应的时域和空域信息,可以保留目标声源方向的信号而抑制其他方向的干扰信号;相干性滤波器方法则通过阵元间不同信号的相关性进行噪音抑制。考虑这两种类型方法的优点,本文提出一种面向二元麦克风小阵列改进的广义旁瓣抵消器语音增强算法,通过在广义旁瓣抵消器的固定波束形成支路上使用相干性滤波器,提高固定波束形成输出信号的信噪比,然后在广义旁瓣抵消器自适应支路利用阵列的时域和空域信息对固定波束形成支路输出的信号中残余噪音进行估计,进而获得增强后目标输出信号。仿真和实际试验表明,本文提出的算法明显优于单独使用小阵列波束形成算法和相干性滤波器算法。      

A robust adaptive beamformer for microphone arrays with a blockingmatrix using constrained adaptive filters

This paper proposes a new robust adaptive beamformer applicable to microphone arrays. The proposed beamformer is a generalized sidelobe canceller (GSC) with a new adaptive blocking matrix using coefficient-constrained adaptive filters (CCAFs) and a multiple-input canceller with norm-constrained adaptive filters (NCAFs). The CCAFs minimize leakage of the target-signal into the interference path of the GSC. Each coefficient of the CCAFs is constrained to avoid mistracking. The input signal to all the CCAFs is the output of a fixed beamformer. In the multiple-input canceller, the NCAFs prevent undesirable target-signal cancellation when the target-signal minimization at the blocking matrix is incomplete. The proposed beamformer is shown to be robust to target-direction errors as large as 200 with almost no degradation in interference-reduction performance, and it can be implemented with several microphones. The maximum allowable target-direction error can be specified by the user. Simulated anechoic experiments demonstrate that the proposed beamformer cancels interference by over 30 dB. Simulation with real acoustic data captured in a room with 0.3-s reverberation time shows that the noise is suppressed by 19 dB. In subjective evaluation, the proposed beamformer obtains 3.8 on a five-point mean opinion score scale, which is 1.0 point higher than the conventional robust beamformer     

Asymptotic S/N results for an adaptive polyspectral canceller usingsample matrix inversion

An adaptive polyspectral canceller configuration is defined, whereby auxiliary canceller channels are formed using distinct monomial expressions of the auxiliary sensor channels. If noises in the auxiliary canceller channels are correlated with the noise in a main channel, then improvement in output signal-to-noise (S/N) power ratio is possible by cancelling in linear fashion the correlated auxiliary canceller channels with the main channel. The convergence performance of the polyspectral canceller is analyzed. A simple expression is derived for the asymptotic S/N efficiency of the adaptive polyspectral canceller as a function of the number of independent input sample vectors used to calculate the adaptive canceller weights and other canceller/noise model parameters. It is shown by simulation for low-order polyspectral cancellers of a specific form with Gaussian inputs that this asymptotic expression is a good approximation of the actual S/N efficiency for a moderate number of input sample vectors. However, for moderate-to-high order polyspectral cancellers, the asymptotic expression is a poor indicator of performance     

Modified time domain orthogonality algorithm for adaptive filters and its applications

A modified time domain orthogonality algorithm (MTDO) for adaptive filters is presented and described. The results of computer simulation show that the algorithm has two characteristics: 1. the same convergence factorc can be used within a fairly wide range of signal to noise ratio (SNR) of input signal. 2. MTDO adaptive noise canceller has a useful characteristic, i. e. at the same signal to noise ratio of input desired signal the input reference signal power is uncorrelated with the convergence factorc. Therefore one adaptive noise canceller can be used more flexibly. The performance of spectral estimates of the MTDO adaptive system is obtained by us experimentally and compared with the least mean square algorithm adaptive system.