基于频域编码技术的冲激噪声抑制方法

冲激噪声干扰是一种突发性的噪声干扰,在其持续时间内强度远大于高斯白噪声,对通信系统的影响非常大.本文提出一种新的基于频域编码技术的冲激噪声抑制方法,通过采用频率特性为伪随机码的滤波器对输入信号的频谱进行随机编码来降低冲激噪声的峰值功率,使冲激噪声转化为近似高斯白噪声.本文从冲激噪声的物理模型出发,分析了频域编码信号的统计特性,论证了频域编码技术抑制冲激噪声的原理.仿真结果表明频域编码技术能简单有效地抑制冲激噪声,抑制效果随着编码长度的增加变佳.     

α稳定噪声中基于正态变换的次优接收机

通信信道中的冲激噪声通常可由对称的α稳定分布(SαS)描述。由于SαS的概率密度函数(PDF)无闭式表达,因此基于Neyman-Pearson准则的解析的最优接收机也不存在。采用解析模型——双参数柯西-高斯混合模型(BCGM)近似SαS的PDF,导出了基于正态化变换的零记忆非线性(NZMNL)限幅器,NZMNL限幅器使得α稳定噪声变换为标准的正态分布噪声。分析了基于该限幅器次优接收机的误码率性能,仿真结果表明对于噪声参数α(1.52.0]时,所提出接收机的性能优于经典的柯西接收机和钳位接收机。     

基于非线性复扩散耦合冲激滤波器的图像放大算法研究简

为了提高放大算法的适应性,采用改进的非线性复扩散和自适应冲激滤波器,提出了一种图像放大方法。根据像素局部方差进行自适应改变扩散门限,扩散图像的虚部除以扩散时间以消除扩散时间的影响,特别是初期扩散近似线性扩散的特性,得到改进的复扩散模型耦合冲激滤波器进行无噪图像放大。对于噪声图像放大,根据像素局部方差进行自适应非线性复扩散,耦合局部方差约束的冲激滤波器增强模糊的图像边缘和细节。自适应非线性复扩散通过局部方差和图像二阶导数相结合分辨边缘和噪声,对噪声进行平滑的同时保持边缘,克服了复扩散不能分辨噪声和边缘的缺陷,同时保持复扩散保护斜坡结构,免除阶梯效应的优点。仿真实验验证了所提算法不仅对无噪图像有较好的放大效果,而且对一定范围的噪声图像也有较好的放大效果。     

一种微惯性/软件接收机超紧组合方案研究

为了改善软件接收机性能,提出一种微惯性/软件接收机非线性超紧组合方案.分析接收机跟踪环路和微惯性测量组件非线性的基础上,提出了非线性跟踪滤波器和非线性组合滤波器的设计方法.基于跑车实验数据完成了该超紧组合系统性能的试验验证.结果表明,在即时码In-phase/Quadra-phase信号较弱的情况下,该超紧组合跟踪环路...     

卫星接收机非线性故障建模与仿真

非线性效应导致接收机设备故障以及性能降级一直是卫星通信系统面临的重要挑战。针对这一问题，本文提出了一种基于行为模型的接收机非线性故障分析方法。首先推导分析滤波器内反射干扰在幅频响应上的表现形式，以此构建滤波器故障描述模型。其次利用幅相转换关系对Saleh模型系数进行修正，建立表征放大器在过饱和点下不同程度的非线性故障模型。然后针对相位噪声相关性对振荡器频率稳定性的影响，利用一阶自回归模型表征在不同相关性相位噪声下，振荡器内存在的非线性故障。最后将滤波器、功率放大器和振荡器的故障模型级联，建立接收机射频前端整体的非线性故障模型，并通过星座图、功率谱以及电路仿真三方面对模型进行仿真分析和验证。实验结果表明，本文建立的故障行为模型能有效表征接收机射频前端存在的非线性故障。      

一种MOE盲自适应空时多用户检测算法的性能分析

将相关矩阵多次幂技术与MOE(最小输出能量)盲自适应空时多用户检测相结合提出了一种新的空时多用户检测算法。并且,从噪声方差、采样数目和u次幂的角度,对这种改进的MOE盲空时多用户检测接收机的性能进行了分析。理论证明和仿真结果表明,这种新的检测技术在噪声方差非常小、采样数目趋于无穷以及u→∞的情况下,它的性能收敛于MMSE盲自适应空时多用户检测。     

DS—CDMA通信中的一种2D-Rake接收机

Rake接收机在3G系统中已被广泛使用,实际应用证明它能够有效对抗移动无线信道中的多径衰落。传统Rake接收机有其时域一维处理的局限性,为获得更好的系统性能,本文在分析空时信道模型的基础上提出一种新的空时2D-Rake接收机算法,它将波束形成技术与Rake相结合。这种波束形成算法能够在干扰方向上完全陷零,其权重仅与阵列天线的导向矢量有关,与接收信号无关。最后简要分析了所提出的2D-Rake接收机的性能。仿真结果表明,这种空时2D-Rake接收机与传统Rake接收机相比,具有较好的性能,而且该算法对噪声具有鲁棒性。     

多天线超宽带通信中的一种盲接收机

针对多天线冲激无线电超宽带通信系统,提出了一种盲的线性接收机。在不需要信道信息的情况下,可以利用经过预编码的空时分组码给接收信号带来的特定结构,直接得到接收机系数,从而恢复出发送符号。仿真表明,随着用于估计的数据块的增加,盲接收机的性能逐渐接近于相关接收。     

一种新的空时2D-RAKE接收机

提出一种新的空时2D-RAKE接收机算法,它将波束形成技术与RAKE相结合。此中波束形成算法在干扰方向上完全陷零,其权重仅与阵列天线的导向矢量有关,与接收信号无关。仿真实验表明,这种空时2D-RAKE接收机与传统2D-RAKE接收机相比,具有较好的性能,而且该算法对噪声具有鲁棒性。这种2D-RAKE接收机与并行干扰抵消(PIC)算法相结合的空时多用户检测的仿真结果表明,多级检测的误码率曲线与第一级重合,采用这种2D- RAKE能够完全消除多址干扰和多径干扰。     

循环神经网络自适应有源噪声对消研究

介绍了一种新颖的非线性逢适应滤波器－－循环神经网络自适应滤波器。由于这种循环神经等效于非线性ＩＩＲ滤波器,具有学习非线性函数到任意的精度及自适应能力,这种滤波器优于线性滤波器,能够适应各种噪声环境。本文将该滤波器用于有源噪声对消,仿真结果表明了这种循环神经网络自适应有源噪声对消系统具有良好的抗噪声性能。     

基于数据选择Householder多级维纳滤波导航接收机空时抗干扰方法

针对抑制GPS信号中期望信号方向的冲激毛刺干扰影响问题,对Householder多级维纳滤波方法进行改进,提出一种数据选择Householder多级维纳滤波器.改进方法用于GPS信号空时抗干扰处理中,可以避免期望信号方向的冲激毛刺干扰对最优权值计算的影响,同时保持期望信号不受影响.仿真结果验证了算法良好的抗干扰性能.     

自适应加权FIR-Myriad混合滤波算法

针对FIR滤波器滤除脉冲噪声以及加权Myriad滤波器滤除高斯噪声的不足,提出基于FIR滤波器和加权WMy滤波器有效组合的一类新的非线性滤波器FIR-WMyH滤波器.利用神经网络中的反向传播算法,在均方误差准则下,推导了一个基于统计梯度的自适应算法.基于稳定α分布脉冲噪声模型下的仿真结果说明了该算法的良好的性能.     

Robust adaptive recovery of spread-spectrum signals with short data records

The problem under consideration is the adaptive reception of a multipath direct-sequence spread-spectrum (SS) signal in the presence of unknown correlated SS interference and additive impulsive noise. An SS receiver structure is proposed that consists of a vector of adaptive chip-based Hampel nonlinearities followed by an adaptive auxiliary-vector linear tap-weight filter. The nonlinear receiver front end adapts itself to the unknown prevailing noise environment providing robust performance over a wide range of underlying noise distributions. The adaptive auxiliary-vector linear tap-weight filter allows rapid SS interference suppression with a limited data record. Numerical and simulation studies under finite-data-record system adaptation show significant improvement in bit-error-rate performance over the conventional linear minimum variance-distortionless-response (MVDR) SS receiver or conventional MVDR filtering preceded by vector adaptive chip-based nonlinear processing.     

基于Householder多级最小模级联相消器导航接收机空时抗干扰方法

该文针对抑制GPS信号中期望信号方向的冲激毛刺干扰影响问题,提出Householder多级最小模级联相消方法,该方法用具有最小模的样本商作为复权,替代Householder多级维纳滤波器的权值计算,并将其用于GPS信号空时抗干扰处理中。此方法能很好地抑制期望信号方向的冲激毛刺干扰对自适应权值计算的影响,且复杂度低,收敛性能好。计算机仿真结果验证了算法的优良快收敛性能和良好的抑制期望信号方向冲激毛刺干扰影响的能力。     

Alpha稳定分布下基于RHMy滤波的MQAM信号码元速率估计方法

针对Alpha稳定分布噪声环境下,传统的MQAM信号码元速率估计方法性能恶化甚至完全失效的问题,本文结合了改进的Myriad类滤波与小波变换法的优点,提出一种基于递归混合Myriad滤波(Recursive Hybrid Myriad filter, RHMy)的高阶消失矩二次小波变换法对MQAM信号进行码元速率估计。首先采用RHMy滤波充分抑制噪声中的脉冲成分,再采用高阶消失矩小波估计码元速率。仿真结果表明,在Alpha稳定分布噪声环境中,相比于多尺度Haar小波变换法、分数低阶循环谱法与基于加权Myriad滤波(Weighted Myriad filter, WMy)的小波变换法,该方法有效的提高了低广义信噪比下的估计精度,同时在不同的脉冲噪声条件下具有较好的鲁棒性。      

稳定分布噪声下基于Merid滤波的跳频信号参数估计

常规时频分析方法是处理跳频(FH)信号的有力工具,但在稳定分布噪声环境下无法有效地实现参数估计。该文提出基于Merid滤波的时频分析方法对跳频信号进行参数估计。Merid滤波器可以有效地抑制稳定分布噪声,该文先对观测信号进行Merid滤波,再采用短时傅里叶变换(STFT)进行参数估计。仿真结果表明,在稳定分布噪声环境中,该方法的跳频信号参数估计性能优于基于分数低阶和基于Myriad滤波的两种时频分析方法。     

Robust MMSE receiver employing Hampel-type nonlinear preprocessing for DS-CDMA communication in impulsive noise

A robust minimum mean square error receiver using Hampel-type nonlinear preprocessing is proposed for mitigating both unknown multiple-access interference and impulsive noise. Simulation results are presented to demonstrate the performance of the proposed receiver structure for three distinct nonlinearities in the presence of additive impulsive Gaussian noise.     

Design of a Sanguine Noise Processor Based Upon World-Wide Extremely Low Frequency (ELF) Recordings

This paper describes the design of a candidate noise processor for the Sanguine receiver based on communication theory considerations and detailed experiments using wide-band recordings of extremely low-frequency (ELF) (3-300 Hz) atmospheric noise. This processor consists of the following elements: 1) a compensating (or whitening) filter; 2) nonlinear notch filtering at frequencies of manmade interference; 3) a post-notch filter nonlinearity; and 4) a phase coherent linear matched filter. Due to the impulsive non-Gaussian nature of the noise, nonlinear processing with a bandwidth considerably greater than the 40-80-Hz signal bandwidth is significantly better than a linear receiver (consisting only of a matched filter and appropriate whitening filters). Simulations using noise recordings from a number of widely separated locations in the world have shown improvements of 7 dB to 20 dB at times of high ELF atmospheric noise levels at the receiver input.     

Fast algorithms for weighted myriad computation by fixed-pointsearch

This paper develops fast algorithms to compute the output of the weighted myriad filter. Myriad filters form a large and important class of nonlinear filters for robust non-Gaussian signal processing and communications in impulsive noise environments. Just as the weighted mean and the weighted median are optimized for the Gaussian and Laplacian distributions, respectively, the weighted myriad is based on the class of α-stable distributions, which can accurately model impulsive processes. The weighted myriad is an M-estimator that is defined in an implicit manner; no closed-form expression exists for it, and its direct computation is a nontrivial and prohibitively expensive task. In this paper, the weighted myriad is formulated as one of the fixed points of a certain mapping. An iterative algorithm is proposed to compute these fixed points, and its convergence is proved rigorously. Using these fixed point iterations, fast algorithms are developed for the weighted myriad. Numerical simulations demonstrate that these algorithms compute the weighted myriad with a high degree of accuracy at a relatively low computational cost     

Signal Detection in the Presence of Atmospheric Noise in Tropics

A new model of HF atmospheric radio noise (ARN) that leads to observed probability distributions of noise is briefly described. The new ARN model is then applied to the detection of known signals in the presence of noise to determine optimal receiver structure for ARN. Probabilities of errors for a linear matched filter and nonlinear (-1/log) and inverted(log)^{2}correlator receivers and a phase coherent binary detector are determined and compared. It is shown that the inverted(log)^{2}correlator combined with the linear matched filter is an optimal receiver in the presence of impulsive noise in tropics. The time statistics of burst noise is applied to design of signals for improved reliability.