1998 Fiscal Year Final Research Report Summary
Performance Analysis of Delayless Subband Adaptive Filter
| Project/Area Number |
09650468
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
計測・制御工学
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| Research Institution | KYOTO UNIVERSITY |
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Principal Investigator |
SAKAI Hideaki Kyoto University, Graduate School of Informatics, Professor, 情報学研究科, 教授 (70093862)
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| Project Period (FY) |
1997 – 1998
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| Keywords | adaptive filter / subband adaptive filter / Hadamard transform / projection method / active noise control / echo canceler |
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| Research Abstract |
The researches of adaptive filters have been done in the some fields such as electronics, communication and active noise control. In recent years, a subband adaptive filter has been used for some applications. A transmission delay appears in the output signal of a conventional subband adaptive filter. This delay is a big problem in the application of an acoustic echo canceler and an active noise control. Recently, a delayless subband adaptive filter has been proposed by Morgan and Thi. However the analysis of the scheme is qualitative and not complete. Also, this scheme require a large amount of computations. The aim of this research is to analyze the delayless scheme quantitatively and to develop a superior method. The following results have been obtained.
(a) quantitative analysis of the conventional delayless adaptive filter
The fuilband adaptive filter in the delayless scheme is obtained by the conversion of the taps of each subband filter. It is clarified that this conversion in the conventional delayless scheme is singular. The conversion matrix is not of full-rank so that the optimal Wiener solution does not belong to its range space.
(b) new method with using the Hadamard transform
A new method using the Hadamard transform is proposed for the subband delayless adaptive scherne with 2^m subbands. It is demonstrated that the above defect is avoided for the 2-band case. The tap conversion from subband filters to a fullband filter can be performed fast because the Hadamard transform does not require multiplication operations.
(c) improvement of the convergence speed by the projection method
When the proposed method is used in some application with an adaptive algorithm such as NLMS, a convergence speed may decrease. The convergence speed can be improved by using the projection method. This effect is demonstrated by some simulations.
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