一种变正则化矩阵的改进多带结构子带自适应滤波算法

定正则化因子的改进多带结构子带自适应滤波(IMSAF)算法在取得收敛速度快和稳态失调误差小之间存在冲突.根据系统噪声抵消原理,设定子带后验误差功率等于子带噪声功率,本文提出了变正则化矩阵的IMSAF算法来解决这一问题.仿真结果证明,所提算法可以同时达到收敛速度快、稳态失调误差小以及追踪速度快等优势.     

自适应渐消UKF算法及其在仅测角被动定位中的应用

针对仅测角被动定位受多径、镜像和干扰源影响,噪声无法准确建模,传统EKF及其改进滤波算法容易发散的问题,将自适应渐消因子引入UKF算法中,调整滤波增益以及状态误差协方差矩阵,提出一种自适应渐消UKF算法,给出了具体的计算流程。仿真了不同雷达诱饵布置干扰下滤波算法的稳定性。仿真结果表明,与传统的EKF以及自适应渐消EKF算法相比,该算法收敛速度更快,稳定性更好。     

基于改进的FXLMS算法的主动降噪耳机系统研究

为了有效解决主动降噪耳机系统的低频噪声,采用变步长FXLMS自适应滤波算法,克服传统定步长收敛速度与稳态误差相互制约的不足,通过构造合适的变步长因子,不但改善算法的收敛速度,而且减少了稳态误差.构建主动降噪耳机模拟控制系统,模拟次级通道路径,对噪声进行处理,仿真实验表明,该算法可以有效降低频噪声,相较于传统算法,该算法具有较好的性能.     

针对拖尾噪声的中值滤波-小波消噪算法分析

与高斯噪声相比,拖尾噪声有更多的异常值,利用传统的小波阈值方法不能对其有效消噪.提出利用中值滤波-小波消噪方法进行处理,首先利用中值滤波抑制异常值,然后利用小波阈值方法消除残留噪声,并给出了适合拖尾噪声的消噪效果评价准则.基于提出的准则,通过实验比较了小波阈值方法与中值滤波-小波消噪方法的消噪效果,结果表明所提出的方法能更好的消除拖尾噪声,具有较好的鲁棒性.     

基于滤波器组的MCAF噪声对消语音增强

在自适应噪声对消语音增强系统中,为了更好地加快自适应收敛速度,又不增加系统的计算复杂度,同时达到较好的增强效果,提出基于滤波器组的多通道自适应滤波(MCAF)语音增强;给出分析滤波器组与综合滤波器组的原型滤波器设计的具体方法.自适应滤波部分采用经典的LMS算法,同时结合多通道自适应滤波(MCAF),实现对含噪语音的处理,以达到增强效果.实验结果表明,相对于传统的子带LMS算法,基于滤波器组的多通道自适应滤波具有更好的性能,且加快了计算速度.     

基于小波的惯导系统初始对准方法研究

目前远程武器系统广泛采用捷联惯性导航系统,该系统在发射前要经过初始对准。由于惯性导航系统中所采用的陀螺仪和加速度表的噪声很大,影响了初始对准,降低了打击精度,为减小噪声影响,提出了一种基于小波消噪理论的捷联惯性制导系统初始自对准方法。研究显示,小波分解滤波可以显著减小惯性器件的噪声,利用经过消噪的信号进行初始对准,滤波器的收敛速度加快,在相同对准时间内精度有明显提高。     

一种成比例系数的子带自适应啸叫抑制算法

啸叫现象会严重影响扩声系统性能.采用自适应滤波算法辨识反馈路径的方式进行啸叫抑制,将成比例系数的无延时多带结构子带自适应滤波(Proportionate Delayless Multiband-structured Subband Adaptive Filtering,PDM-SAF)算法应用到啸叫抑制系统中.该算法继承了子带自适应滤波算法收敛速度快的优点,并考虑到反馈路径的稀疏特性和系统对实时性的要求,采用成比例系数的步长控制和无延时的误差计算方法.仿真结果表明,当扩声系统的反馈路径具有稀疏特性时,PDMSAF算法可以加快自适应滤波的收敛和跟踪速度.     

一种应对窄带非线性主动噪声控制的混合结构

分析参考信号为窄带信号、初级路径为非线性路径、次级路径为非最小相位系统的主动噪声控制（ANC）的初级噪声特性,探究有限脉冲响应（FIR）反馈预测结构和前馈函数链接人工神经网络（FLANN）结构的消噪原理,并探讨其各自的优势及局限性.通过分析总结,本文提出FLANN-FIR混合结构ANC系统,该系统对FIR反馈预测结构和前馈FLANN结构进行优势互补,不仅可以消除可预测部分噪声,对不可预测部分噪声一样具有抑制作用.仿真表明,在不同信噪比参考信号和不同非线性初级路径下,提出的混合结构都具有良好的稳态误差和收敛速度.     

基于形态学运算和自适应阈值的心电信号消噪

抑制信号中的噪声干扰,是心电(ECG)信号预处理中的关键步骤.针对传统形态学滤波损失有用信号的缺陷,本文提出了一种基于形态学运算和自适应阈值的ECG信号消噪算法.首先,对含噪ECG信号进行形态学滤波和形态学峰谷提取运算;然后,估算形态学峰谷信号中时变噪声的即时方差,并依据3σ准则对峰谷信号进行自适应阈值处理,保留其中的有用信号;最后,将阈值处理结果与形态学滤波结果相加,作为ECG信号消噪处理的最终结果.仿真试验与实际应用结果表明,该算法不仅可以有效去除时变噪声的干扰,而且较好地保持了ECG信号的特征形态,处理效果明显优于以往的形态学滤波算法,且比基于平稳小波变换的消噪算法更适用于非平稳ECG信号的消噪处理.     

LMS与RLS算法仿真消噪对比研究

讨论了RLS（递归最小二乘）和LMS（最小均方）自适应滤波算法及原理,对两种算法进行了系统全面的分析,对比研究了各自的优势及不足,提出了两种算法在语音消噪仿真中的算法实现,对实际语音信号进行了仿真消噪,研究表明选用算法对语音消噪是明显有效的,RLS自适应消噪算法及LMS自适应噪声抵消算法具有很强的实际应用价值。     

Noise‐Robust Speaker Recognition Using Subband Likelihoods and Reliable‐Feature Selection

We consider the feature recombination technique in a multiband approach to speaker identification and verification. To overcome the ineffectiveness of conventional feature recombination in broadband noisy environments, we propose a new subband feature recombination which uses subband likelihoods and a subband reliable‐feature selection technique with an adaptive noise model. In the decision step of speaker recognition, a few very low unreliable feature likelihood scores can cause a speaker recognition system to make an incorrect decision. To overcome this problem, reliable‐feature selection adjusts the likelihood scores of an unreliable feature by comparison with those of an adaptive noise model, which is estimated by the maximum a posteriori adaptation technique using noise features directly obtained from noisy test speech. To evaluate the effectiveness of the proposed methods in noisy environments, we use the TIMIT database and the NTIMIT database, which is the corresponding telephone version of TIMIT database. The proposed subband feature recombination with subband reliable‐feature selection achieves better performance than the conventional feature recombination system with reliable‐feature selection.     

分布式子带自适应滤波算法

为了解决分布式最小均方算法在输入信号相关性较高时收敛速度较慢、分布式仿射投影算法计算复杂度较高等问题,本文提出了两种分布式子带自适应滤波算法,即递增式和扩散式子带自适应滤波算法.分布式子带自适应滤波算法将节点信号进行子带分割来降低信号的相关性,从而加快收敛速度.由于用于子带分割的滤波器组中包含了抽取单元,所以分布式子带自适应滤波算法和对应的分布式最小均方算法的计算复杂度相近.仿真结果表明,与分布式最小均方算法相比,分布式子带自适应滤波算法具有更好的收敛性能.     

Quantisation noise control in perceptual audio coding using low selectivity filter banks

The problem of computing, in a subband audio coder, the maximum quantisation noise power that can be injected in each band to ensure transparent coding when low selectivity filter banks are used, is addressed. A low complexity strategy, taking into account the frequency responses of the synthesis filter bank, is proposed for achieving an overall distortion due to quantisation noise always below the masking threshold (provided by a psycho-acoustic model) for any length prototype filters.     

Adaptive Modulation with Channel Estimation in High-Speed Packet-Based OFDM Communication Systems

1　Introduction　TherapidgrowthofInternetandmobilecommu nicationssuggestthatwirelesshigh speeddataser viceswillbeingreatdemand .Beyond 3Gsystemsaimingatdataratesupto 2 0Mbpsorevenhigherareunderintensivestudy[1～ 3] .Butprovidinghighdataratesinadversewirelesschannelsischalleng ing .OFDMhasbeenconsideredthemostpromisingsolutionforbeyond 3GbecauseofitsrobustnesstoInter SymbolInterference (ISI)andhighspectrumefficiency[4] .　OFDMhasanumberofapplications,includingAsymmetricDigitalSubscriber…     

Subband image coding using entropy-coded quantization over noisychannels

Under the assumption of noiseless transmission the authors develop two entropy-coded subband image coding schemes. The difference between these schemes is the procedure used for encoding the lowest frequency subband: predictive coding is used in one system and transform coding in the other. After demonstrating the unacceptable sensitivity of these schemes to transmission noise, the authors also develop a combined source/channel coding scheme in which rate-compatible convolutional codes are used to provide protection against channel noise. A packetization scheme to prevent infinite error propagation is used and an algorithm for optimal assignment of bits between the source and channel encoders of different subbands is developed. It is shown that, in the presence of channel noise, these channel-optimized schemes offer dramatic performance improvements     

Optimal filter banks for signal reconstruction from noisy subbandcomponents

Conventional design techniques for analysis and synthesis filters in subband processing applications guarantee perfect reconstruction of the original signal from its subband components. The resulting filters, however, lose their optimality when additive noise due, for example, to signal quantization, disturbs the subband sequences. We propose filter design techniques that minimize the reconstruction mean squared error (MSE) taking into account the second order statistics of signals and noise in the case of either stochastic or deterministic signals. A novel recursive, pseudo-adaptive algorithm is proposed for efficient design of these filters. Analysis and derivations are extended to 2-D signals and filters using powerful Kronecker product notation. A prototype application of the proposed ideas in subband coding is presented. Simulations illustrate the superior performance of the proposed filter banks versus conventional perfect reconstruction filters in the presence of additive subband noise     

基于Contourlet变换和模糊理论的红外图像增强算法

红外图像具有噪声大、对比度低等特点,针对该特点,提出了一种基于Contourlet变换与模糊理论的红外图像增强算法。首先对图像进行Contourlet变换,得到多尺度多方向的低通子带和带通子带。对低通子带,进行基于子带系数最大最小值的线性变换,提高图像的整体对比度;对于带通子带,先估计噪声阈值,对子带系数进行抑制噪声处理,然后通过模糊增强算法,对高频系数进行非线性增强,增强目标边缘纹理的特征,抑制背景信号。最后经过Contourlet逆变换得到对比度增强,噪声被抑制的图像。经过算法仿真,与几种现有的图像增强算法相比,该算法更能有效地抑制噪声,增强图像的对比度,突出图像的边缘与细节纹理信息。     

基于传声器阵列的近场宽带波束形成方法

提出了一种适合于近场宽带传声器阵列处理的空时子带波束形成新方法。该方法通过将一个空域子带阵列和时域子带多速率滤波器组合并来同时获得空域和时域两种子带系统的优点。计算机仿真比较了其与全带自适应波束形成方法的性能,结果表明该方法对干扰有较强的抑制能力,改善了宽带波束形成频域不一致问题,并且能够并行处理,为实际语音通信系统的应用提供了一种有利途径。     

Noise reduction in oversampled filter banks using predictivequantization

We introduce two methods for quantization noise reduction in oversampled filter banks. These methods are based on predictive quantization (noise shaping or linear prediction). It is demonstrated that oversampled noise shaping or linear predictive subband coders are well suited for subband coding applications where, for technological or other reasons, low-resolution quantizers have to be used. In this case, oversampling combined with noise shaping or linear prediction improves the effective resolution of the subband coder at the expense of increased rate. Simulation results are provided to assess the achievable quantization noise reduction and resolution enhancement, and to investigate the rate-distortion properties of the proposed methods