一种简化的自适应回声抵消算法及其应用分析

声学回声抵消器可视为一横向自适应滤波器,声学回声抵消技术在现代信号处理中得到越来越广泛的应用。在讨论了声学回声抵消基本原理后,提出了一种基于自适应滤波技术的声学回声抵消简化频域FDAF—MDFTP算法,并对该算法特性以及对声学回声返回损失增加度的影响进行了分析。最后,基于该频域算法对室内声学回声抵消进行了模拟计算,可得到很好的回音抵消效果。     

基于TMS320DM642实现的一种低复杂度回声抵消器

以TMS320DM642定点DSP为平台,实现了一种低复杂度并适应双端会话情况的回声抵消器.在算法上.为提高双端会话的鲁棒性,采用了双回声路径模型(two echo path moolel,TEPM)作为基本框架;为降低计算的复杂度,采用了多延时分块频域自适应滤波器(multi-delay block frequencydomain adaptive filter,MDF)估计回声路径的冲击响应.在实现上,针对DSP的并行执行能力和指令集的单指令多数据(SIMD)特性对主要运算进行了线性汇编级的优化.测试表明,这种回声抵消器可以在0.45%CPU占用率下处理128 ms路径延时的组合声源信号(composite source signal,CSS)和实际声源信号的回声.     

基于DSP Builder的回波抵消器设计与实现

针对通信中的回波问题,基于自适应滤波的LMS算法,设计了自适应回波抵消器。并基于利用FPGA芯片,在DSP Builder平台上,有效结合MatLab／Simulink和Quartus II设计工具,根据模块化设计思想实现了LMS算法自适应回波抵消器硬件电路设计。软件仿真和系统FPGA硬件实测结果表明,该设计方法使回波抵消器的FPGA硬件实现更加简便快捷。     

基于DSP Builder的回波抵消器设计与实现

针对通信中的回波问题,基于自适应滤波的最小均方（LMS）算法,设计了一个自适应回波抵消器。基于FPGA芯片,在DSP Builder平台上,有效结合MATLAB/Simulink和Quartus Ⅱ设计工具,根据模块化设计思想实现了LMS算法自适应回波抵消器硬件电路设计。软件仿真和系统FPGA硬件实测结果表明,该设计方法使回波抵消器的FPGA硬件实现更加简便快捷。     

无双端会话检测回声抵消系统

提出一种无双端会话检测自适应回声抵消系统,这种系统突破了当前自适应回声抵消器必须进行双端会话检测的限制。仿真结果表明这种无双端会话检测回声抵消器在所有工作模式下均能取得理想的回声抵消效果。     

一种改进的双通道滤波回声抵消算法——过采样无延迟子带方法

在强相关大动态范围语音作用下,回声抵消器直接更新上千阶自适应滤波器系数,计算量大、收敛速度慢。采用子带分析与合成的方法能够减少计算量和提高算法的收敛性能,但子带的分析与合成也给线路中引入了信号延迟。提出了一种改进的双通道滤波回声抵消算法,将子带自适应滤波器映射到全频带滤波器,减少了信号的延迟;同时采用双通道滤波器。使系统工作在较小残余回声功率下。仿真结果表明,改进算法在单边会话情况下收敛快．具有较好的回声抵消效果。     

元器件快讯

独立式TelinnovationTM 回波抵消器德州仪器(TI)推出的一整套基于数字信号处理器 (DSP)的回波抵消解决方案 ,能够有效抵消多达512个话音信道所产生的回波。该方案基于TI的TMS320C55x(tm)DSP平台及Telinnovation回波抵消软件 ,改进了回波抵消器的算法 ,并大大提高了信道密度。通过采用C55xDSP ,该方案可获得多达512个信道密度 ,从而提供了每信道占用空间最小且功耗最低的回波抵消器。这种独立式Telinnovation回波抵消器可为网络设备制造商提供整套回波抵消器系统 ,该系统采用了最广泛的回波抵消技术。它的自适应降噪(ANR特性)采用…     

回声抵消器的DSP方案

阐述了高速DSP芯片数字通信系统回声抵消中的应用设计。     

回声抵消器的应用和测试

在移动通信中，回声抵消器（ＥＣ）对改善话音效果起着重要的作用。它可用于国际长途电路。Ｔ１／ Ｅ１多信道回声抵消、话音／ ＩＰ网关、ＰＣＳ无线基站、无线电话、话音／ＡＴＭ及帧中继等需要抑制回声的电路中。１基本用途 回声抵消器的基本用途是控制话音激励信号的回声。在任何２线或２／４线结合的电话电路上，由于阻抗失配会产生回声。回声抵消器可把回声减少到容许的水平。在回声抵消器发送输入端出现的回声，是远端7来话话音失真和时延的结果。位于电路４线部分的回声抵消器，用于减少发送通道的近端回声，通过从近端回声中减去估…     

基于IPNLMS算法的回声抵消器的设计

主要针对电话系统中的线路回声进行研究,分析了线路回声的基本原理与抑制方法,深入研究、设计并实现了基于IPNLMS自适应算法的回声抵消算法。测试结果表明,所设计算法能够很好地抵消延迟长达120 ms以内的回声信号,语音质量的PESQ得分值由回声抵消前的2.2分左右提高到回声抵消后的3.5分以上。     

Fast initialization of data-driven Nyquist in-band echo cancellers

A echo canceller fast training scheme for data-driven Nyquist in-band echo cancellers is presented. This scheme simultaneously estimates the desired near and far echo canceller coefficients by sending a special periodic training sequence and correlating a segment of the sequence with the real echo samples. The requirements and the generation of the training sequence are discussed. It is shown that the fast training method can also provide the parameters for the fast initialization of the phase roll compensator in the echo canceller, and thus complete the fast training of the entire echo canceller. Compared to the conventional LMS training and other training methods, this scheme provides accurate estimates of the echo canceller coefficients in a significantly reduced training time     

Performance analysis of an echo-cancellation arrangement thatcompensates for frequency offset in the far echo

Analytical and experimental results are presented for the performance of one echo canceller arrangement. It consists of a data-driven echo canceller having a so-called cross-coupled structure, which is followed by a rotator and a phase-locked loop (PLL). A cross-coupled echo canceller structure without a PLL is analyzed first. Expressions for speed of convergence and achievable echo-return-loss enhancement (ERLE) in the presence of frequency offset are derived. These results are compared in previously published results for a noncross-coupling echo canceller structure. Specifically, it is shown that the cross-coupled structure converges twice as fast as the noncross-coupled structure and provide an achievable ERLE that is about 6 dB better. The joint adaptation of the echo canceller and the PLL is then studied. It is shown that it is always possible to choose design parameters for the echo canceller which are consistent with adaptation requirements under double-talking conditions, provided that the PLL is properly engineered. The sensitivity of the performance of PLL to the power level of the far echo, as well as possible solutions to this problem, are discussed     

与VoIP声码器结合的回声消除器

NLMS算法是回声消除器中最常用的算法之一,然而语音信号的强相关性使NLMS(归一化最小均方)算法的收敛速度变慢。鉴于VoIP(网络电话)常用的低速率声码器大多基于LP(线性预测)编码,给出了一种与声码器结合的回声消除器,通过利用从解码端获得的LP系数和激励信号,省去了对去相关滤波器系数的计算,并且不再需要专门的前置滤波器为远端信号去相关,同时又改善了回声消除器性能。仿真结果表现出更高的收敛速度和回声抵消量。     

Nonlinear Echo Cancellation of Data Signals

This paper describes a new technique for implementing an echo canceller for full-duplex data transmission (such as in digital subscriber loops and volceband data sets). The canceller can operate in spite of time-invariant nonlinearities in the echo channel or in the implementation of the echo canceller itself (such as in the D/A converters). The basic structure of the linear echo canceller is not changed, but taps are simply added to account for the nonlinearity. The number of taps which must be added depends on the degree of nonlinearity which must be compensated. Numerical results based on computer simulation are given which show that typical nonlinearities encountered in MOS D/A converters can be compensated by a relatively small number of taps added to the linear echo canceller, and substantial improvement in the cancellation results.     

一种新型的空间声回波消除器

空间声回波消除因回波通道冲激响应长达几百毫秒一直是信号处理领域的一个难题.本文设计了空间声回波消除器,提出了自正交轮流受限分段批处理频域LMS(PBFLMS)算法,可以达到收敛性能、失调性能、计算复杂度以及延时等性能之间的折衷,并结合空间声回波消除器的具体应用,改善了该算法。最后将空间声回波消除器在ATD-C30开发仿真系统中实现,得到了比较满意的结果.     

语音及数据传输中的回波对消问题

文章主要介绍电话系统中的回波产生的机理，回波对消的理论基础，回波对消器的实现方法及有关问题。     

A data-driven multitone echo canceller

A data-driven echo canceller for full-duplex data transmission with multitone modulation is presented. This multitone echo canceller (MTEC) is not impaired by eigenvalue-spread problems that are inherent in signal-driven echo cancellers-it has numerical performance and cancellation range that equals, and in most cases exceeds, that of data-driven echo cancellers used in data transmission with baseband or quadrature amplitude modulation. The method makes use of frequency-domain updating, but time-domain implementation of the canceller. It introduces no delay into the received signal path and presents no special difficulties for interframe interpolation between near-end echo, far-end echo, or far-end data signal. The authors also investigate the fast initialization and the special case of far-end frequency offset in the echo signal     

An Adaptive-Step Sign Algorithm for Fast Convergence of a Data Echo Canceller

This paper proposes an echo cancellation algorithm that can be used for full-duplex digital data transmission over existing twisted-pair cables. The proposed algorithm is a form of the "sign algorithm." A new adaptation method is introduced to change the canceller step size according to the residual echo level by using the correlation between the echo and the error signal. The adaptation method can increase the echo canceller convergence speed by an order of magnitude over the conventional sign algorithm. An echo canceller utilizing the proposed algorithm is suitable for VLSI implementation, because it requires no multibits analog-to-digital converter. Theoretical analysis and parameter optimization are carried out. The rapid convergence property of the algorithm is verified by computer simulation as well as experiments.     

移动通信网回声抑制器的使用和设置

本文对回声产生的原理进行了分析,结合移动通信网中的回声问题,对移动通信网中的回声抑制方法和回声抑制器设置原则进行了阐述,解决了移动和PSTN间通话存在的回声问题,有效利用了回声抑制器设备资源。     

A 125-MHz mixed-signal echo canceller for Gigabit Ethernet oncopper wire

A discrete-time analog echo canceller is described that reduces the echo in the front end of Gigabit Ethernet twisted-pair interfaces. Echo cancellation in the analog domain by means of four taps reduces the complexity of the digital echo canceller and crosstalk cancellers. Designed in a 0.4-μm CMOS technology, the circuit employs an LMS algorithm to adapt to the cable length and impedance discontinuities, providing an echo suppression of 10 dB. The design operates at 125 MHz while consuming 43 mW from a 3-V supply