灵巧噪声干扰与自适应旁瓣对消对抗的仿真与分析

灵巧噪声干扰与自适应旁瓣对消(Adaptive Side-Lobe Canceling,ASLC)是电子对抗领域的两种关键技术.基于此,介绍常见的灵巧噪声干扰样式,如脉冲复制转发干扰和卷积噪声干扰,从ASLC的原理出发,利用递归最小二乘算法(Recursive Least Squares,RLS)对经过ASLC处理后的...     

神经网络在自适应噪声抵消中的应用研究

本文将基于正交最小二乘的RBF神经网络算法引入自适应噪声对消中,提出一种基于最小二乘算法和径向基网络的自适应噪声抵消(adaptive filter based on least square algorithm and radial basis network,简称OLSRBFAF)算法。RBF网络因其具有良好的推广能力,简单的结构和快速的训练过程等诸多优点已被成功应用于很多领域。RBF神经网络中关键因素是基函数中心的选取,中心选取不当构造出来的RBF网络的性能一般不能令人满意。利用正交最小二乘(orthogonal least squares,简称OLS)算法选取RBF网络中心,解决了径向基函数网络构造这一关键问题。并由于OLS算法中采用了最小二乘(least-square,简称LS)准则,其对时变信道具有快速跟踪的能力。利用MATLAB仿真结果分析可知,通过将两种算法结合引入自适应噪声抵消系统,使该系统具有误差更小,消除噪声能力更强的优点。     

基于小波域的图像噪声类型识别与估计

提出了一种基于小波域分解的类型识别方法．该方法利用噪声图像的小波高频子带系数能量分布,对图像中最常出现的两类噪声：高斯噪声和椒盐噪声进行识别,并在此基础上对高斯噪声的方差和椒盐噪声的密度进行了估计．对大量含噪图像的实验结果表明：该方法对图像噪声类型的识别和噪声大小的估计都比较准确．     

基于递归最小二乘的DS-SS系统抗窄带干扰技术

该文针对DS-SS系统的未知窄带干扰,通过分析接收信号统计特性,提出递归最小二乘(RLS)滤波的干扰抑制算法。与盲递推最小二乘算法相比,减少了约束条件,降低了复杂度,而且克服了LS滤波算法不能实时处理的弱点,可以实现快速算法。仿真结果表明,该算法抑制干扰对DS-SS系统性能改善优于自适应线性滤波算法,而且不用考虑算法的收敛性,更利于工程应用。     

脉冲噪声环境下的恒模盲均衡算法

α稳定分布噪声导致现有的基于梯度下降法的恒模盲均衡算法(SGD-CMA)失效.通过分析厚拖尾噪声对现有算法的影响,给出了2种改造算法,即韧性梯度下降恒模盲均衡算法(SGD-RCMA)和递归最小二乘恒模盲均衡算法(RLS-RCMA).仿真表明2种改造算法比传统的恒模盲均衡算法具有更好的适用性,不仅适用于高斯噪声环境而且适合于脉冲噪声环境.同时RLS-RCMA与SGD-RCMA相比具有更快的收敛速度和更好的码间干扰抑制能力.     

Parallel interference cancellation for carrier frequency offset in OFDM assisted with recursive least squares algorithm

Parallel interference cancellation (PIC) assisted with recursive least squares (RLS) algorithm is proposed to cancel the interference due to the carrier frequency offset (CFO) in orthogonal frequency division multiplexing (OFDM) system. The proposed algorithm is composed of two stages, which are RLS scheme and PIC scheme. RLS scheme is selected to compensate the frequency offset in the time domain in the first stage, and the interference induced by residual frequency offset is canceled by the PIC scheme in the frequency domain in the second stage. The result of bit error rate (BER) shows that its performance is robust for cancellation as comparison criteria, even though the frequency offset is 0.45. The 16QAM constellation is also simulated to observe the improvements from the proposed suppression schemes.     

基于多特征联合处理的灵巧噪声干扰识别

灵巧噪声干扰已成为一种作用于新体制相参雷达的重要干扰类型.为了有效抑制该类干扰,提出一种基于多维特征的抗干扰方式.通过分析DRFM产生灵巧噪声干扰原理,建立目标与干扰信号模型;在分析对比两类信号特性的基础上,提取包络起伏参数、相位门限内概率及盒维数特征以表征目标与干扰信号在波形、相位及尺度信息上的差异;为了进一步提高干扰识别性能,加入表征信号复杂度的近似熵特征,分析表明该特征因子对噪声具有较强的鲁棒性;最后采用支撑向量机对提取的多维特征进行处理以实现灵巧噪声干扰的识别对抗.仿真实验表明,该方法对目标和干扰的正确识别率高且基本不受干噪比影响.     

多径CDMA信道下一种新的RLS空时接收机

针对多径CDMA信道下的多用户检测中出现的线性约束二次规划问题提出一种新的递归最小二乘算法，该算法可以完全避免因约束而引进的矩阵求逆运算(相对常规的递归最小二乘算法)，并将这种算法与CDMA多用户系统结合起来给出了一种新的自适应接收机，仿真结果表明了这种算法是有效的(无论在检测性能上还是在收敛性能上)。     

核递归最小平均P范数算法

在强脉冲噪声干扰背景中,核递归最小二乘(Kernel Recursive Least Square,KRLS)算法和核递归最大相关熵(Kernel Recursive Maximum Correntropy,KRMC)算法对非线性信号预测性能严重退化,对此提出一种核递归最小平均P范数（Kernel Recursive Least Mean P-norm,KRLMP）算法。首先运用核方法将输入数据映射到再生核希尔伯特空间。其次基于最小平均P范数准则和正则化方法,推导得到自适应滤波器的最佳权向量,其降低了非高斯脉冲和样本量少的影响。然后利用矩阵求逆理论,推导得到矩阵的递归公式。最后利用核技巧得到在输入空间高效计算的滤波器输出和算法的迭代公式。alpha稳定分布噪声背景下Mackey-Glass时间序列预测的仿真结果表明:KRLMP算法与KRLS算法和KRMC算法相比,抗脉冲噪声能力强,鲁棒性好。      

关于接收机的相位噪声

接收机的相位噪声实际上专指频率合成器的相位噪声,而频率合成器的相位噪声是衡量其短期稳定度的一个技术指标,目前国内外的频率合成器基本采用锁相环(PLL)或多个锁相环的方式.频率合成器的频率稳定度包括长期稳定度和短期稳定度.长期稳定度一般由基准频率源(通常为恒温晶振或温度补偿晶振,或由外部基准频率源)决定,短期频率稳定度由锁相环决定(环路参数、部件如压控振荡器).相位噪声早期也称为相位抖动,在时域多用阿仑方差表示,在频域多用相位噪声(偏离载波某个频偏处的单位带宽内相位噪声功率相对主载波的功率低多少,通常用dBc/Hz表示,dBc中的c表示相对值)表示.     

基于折叠技术的多相结构信道化接收机设计

基于传统方法实现的多相结构信道化数字接收机资源占用过多,资源利用率不高,这一问题在信道数很多的时候显得尤为突出。文中提出了一种基于折叠技术的实现方案,通过对其中资源占用最多的部分进行适当的折叠处理,可以节约大量资源。系统各模块采用VHDL语言实现,通过Modelsim软件仿真证明了本方案可行,相比未采用折叠的方案而言资源的占用量明显减少,资源利用率提高了将近50%。     

Understanding noise in SIS receivers

A simple laboratory test receiver has been built and used to examine some interesting aspects of heterodyne mixing with superconductor-insulator-superconductor tunnel junctions. Experiments made over the frequency range 220 GHz–490 GHz using junctions of both the Pb/Bi/In-type and the Pb/In/Au-type indicate that, in the majority of cases, a receiver may be characterized through a few simple measurements made external to it's dewar. We also show that, at high local oscillator drive levels, excess mixer noise may be generated which may be removed by the application of a magnetic field. This is of particular relevance to high frequency mixing where Josephson interference may be strong. Finally, it is observed that even in the presence of severe interference a stable bias point, free from excess mixer noise, is often possible.     

Effect of thermal noise and APD noise on the performance ofOPPM-CDMA receivers

The effect of thermal noise and avalanche-photodiode (APD) noise on the performance of optical overlapping pulse-position modulation/code-division multiple-access (OPPM-CDMA) systems with and without double optical hardlimiters is examined. Comparisons with the corresponding optical on-off keying/CDMA (OOK-CDMA) systems are presented as well. The maximum data rate that can be achieved under laser pulsewidth and bit error rate constraints is determined. It is shown that about 10 dB increase in the average power, with respect to the Poisson shot-noise-limited system, is required to compensate for the performance degradation due to thermal noise and APD noise. Moreover, it is indicated that for a bit error rate not exceeding 10^-9, a laser pulsewidth of 0.03 ns, and an average received optical power of -55 dBm, a data rate of more than 3 Gb/s can be achieved per channel when using OPPM-CDMA systems with double optical hardlimiters     

基于双麦克风降噪技术的语音识别系统

语音控制是智能化设备的重要控制手段,而语音识别是实现语音控制的关键技术。为了设计一种可靠的、抗干扰性强的产品,提出了一种基于双麦克风降噪技术的语音识别系统。该设计运用ROHM公司的BU8332KV芯片作为语音识别前端处理的核心,利用其双麦克风降噪技术来解决语音识别中的噪声问题,结合单片机和语音识别芯片,应用于按摩椅的语音控制系统中。经过非特定人的语音识别系统的静态和噪声环境下测试,结果表明在噪声环境下,该系统有较高的识别率,适用于按摩椅的应用环境,也适合在其他有环境噪声干扰的语音识别系统中推广应用。     

Intensity noise in ASK coherent lightwave receivers

The effect of local oscillator intensity noise on the performance of two and three-branch ASK homodyne receivers and single-branch ASK heterodyne receivers is investigated and an optimum local oscillator power is found. At optimum local oscillator power, both the three-branch and heterodyne receivers are found to have a somewhat better sensitivity than the two-branch receiver. If the local oscillator power is high than the optimum value, the three-branch receiver is significantly less sensitive to intensity noise than the other two receivers     

阵列接收噪声系数分析

通过雷达威力方程说明噪声系数的重要性,分析了单级接收、级联接收、无源阵接收和有源阵接收的噪声系数,给出了噪声系数的计算,总结了阵列接收机噪声系数的特点。     

基于噪音谱分析的新型指数空间匹配滤波器设计

光学相关识别过程中,为减小输入场景中背景噪音对输出相关点的影响,通过分析背景噪音和目标图像的傅里叶谱,在匹配滤波函数中引入一由背景噪音傅里叶谱确定的指数函数,通过指数函数对匹配滤波函数振幅进行非线性调制,使设计的指数型空间匹配滤波器对背景噪音谱透过率小于目标图像谱透过率,从而增加输出相关平面上的信噪比,以实现相关点的正确探测。模拟结果表明当参量m由0增加到1.2时,相关峰值下降2.28倍,信噪比增加3倍。模拟和实验结果均表明:与纯相位匹配滤波器相比其抗噪能力得到明显改善。     

Quantum noise and excess noise in optical homodyne and heterodyne receivers

A parallel development of the semiclassical and quantum statistics of multispatiotemporal mode direct, homodyne, and heterodyne detection using an ideal (except for its subunity quantum efficiency) photon detector is presented. Particular emphasis is placed on the latter two coherent detection Configurations. The primary intent is to delineate the semiclassical theory's regime of validity and to show, within this regime of validity, how the quantum theory's signal quantum noise, local oscillator quantum noise, the quantum noise incurred because of subunity detector quantum efficiency, plus (for heterodyning only) image band quantum noise produce the quantitative equivalent of the semiclassical theory's local oscillator shot noise. The effects of classical fluctuations on the local oscillator, and the recently suggested dual-detector arrangement for suppressing these fluctuations, are treated. It is Shown that previous studies of this arrangement have neglected a potentially significant noise contribution.     

基于BSResSKGRU的雷达信号调制样式识别

针对基于图像识别的雷达信号调制样式识别方法生成图像耗时长,收敛速度慢,且在低信噪比条件下识别准确率低的问题,提出了一种新的雷达信号调制样式识别模型。此模型将雷达信号时间序列经简单预处理后直接作为网络输入,避免了将信号转换为图像的复杂过程;网络能够自主提取雷达信号空间和时间两个方面特征,完善了特征提取的方式;同时,对网络结构进行了优化,并引入了选择性核网络,以获取特征在不同尺度上的重要信息。实验结果表明,此模型在低信噪比条件下具有较快的训练速度和较高的识别准确率。