Lifeng Zhang

Publication Date


Document Type


First Advisor

Tahernezhadi, Mansour

Degree Name

M.S. (Master of Science)

Legacy Department

Department of Electrical Engineering


Adaptive filters; Echo suppression (Telecommunication)


Adaptive signal processing application in acoustic echo cancellation usually involves adaptive filters with hundreds of taps. Such a long length adaptive filter results in high computational complexity and slow convergence which makes it very difficult to be implemented in real time as well as precluding it from some low cost applications. Subband techniques have recently been developed for adaptive filters to solve these problems. However, some approaches of conventional subband techniques insert signal path delay which limits its use in lowdelay application. This thesis presents a new type of subband adaptive filter architecture in which the adaptive weights are computed in subbands, then, collectively transformed into an equivalent set of wideband filter coefficients. In this manner, it is possible to obtain a low delay in signal path due to the introduction of bandpass filters and keep advantage in convergence speed by comparison with some traditional techniques. Computer simulation is also presented in the thesis using 3 2-subband polyphase FFT FIR LMS and recursive LMS implementations. The computer simulation results for 16-bit fixed point polyphase FFT FIR LMS structure are also provided.


Includes bibliographical references (pages [84]-85)


x, 85 pages




Northern Illinois University

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