回波消除器的研究

【作者】 欧雄兵；

【导师】 殷福亮；

【作者基本信息】 大连理工大学 ， 信号与信息处理， 2003， 硕士

【摘要】 随着语音通信技术的发展，人们对语音通信质量的要求越来越高。回波消除技术能有效地解决长距离电话网络、IP电话、免提电话和视频会议等通信系统中的回波问题，明显地改善语音通信质量，具有广阔的市场前景。 本论文主要研究自适应回波消除器，包括电回波消除器和声回波消除器两个方面。自适应回波消除器可以生成一个模拟的回波信号。从近端信号中减掉该模拟回波信号，就可以实现回波消除。 本文是按以下几方面组织的： 第一章简要介绍了回波消除器的背景知识，包括回波产生机理，自适应回波消除器的基本原理和基本构成模块，最后介绍了本文的主要工作。 第二章主要讨论了各种自适应滤波算法。根据实际通信系统的要求，主要研究了减小自适应算法的计算复杂度，以便进行实时处理，降低系统成本。还探讨了各种自适应滤波算法之间的联系和区别。 第三章介绍了子带技术和子带自适应滤波器，着重讨论了子带自适应滤波技术的好处和子带混叠对回波消除器的影响。 第四章结合回波消除器的实现，研究了加快收敛的实用方法和减少回波消除器计算量的措施。提出了一种新的基于双辅助滤波器结构的回波消除器，讨论了有限精度的影响和用TITMS320C549DSP实现的有关问题。 第五章和第六章给出了电回波消除器和声回波消除器的测试结果以及未来工作展望。其中主要测试指标为稳态残留回波和收敛速度。更多还原

【Abstract】 The echo problem exists in many fields, such as large loop delay telecommunication channels, mobile phone system and teleconference system etc. It’s difficult to get smooth conversation without proper echo control. So to support high-speech-quality voice communication, the technology of echo cancellation has been a very active research field in the recent years.This paper is focused on the adaptive echo canceller, which includes the electric echo canceller and the acoustic echo canceller. The basic principle of the adaptive echo canceller can be summarized as follows:Adaptively synthesize a replica of the echo and subtract it from the echo-corrupted signal.This paper is organized as follows:The background knowledge about the echo canceller such as echo mechanism, the basic principle and basic components is introduced in the first chapter.In the second chapter, many kinds of adaptive filter algorithms are discussed. To meet the requirement of the real-time processing, we put more emphasis on the fast algorithms and the algorithms that can get a tradeoff between the convergence performance and the compute complexity. The correlation and the difference of these algorithms are also discussed.The subband technology and the subband adaptive filters are introduced in the third chapter. We especially focus on the merit of the subband adaptive filter technology and the influence to the performance of the echo canceller because of the subband alias.Then according to the implementation of the echo canceller, we discuss the applied methods to improve the convergence speed and reduce the computation complexity. A new kind of echo canceller based on the structure of dual-assistant filters is proposed to solve the double talk detection problem. Other implementation issues such as finite precision effects and the realization based on TI TMS320C549 are also discussed.Finally, the test results are given to demonstrate the performance of the design electric echo canceller and acoustic echo canceller, where the steady residual echo and the rate of convergence are the main indexes.更多还原