U.S. Philips Corporation

Petrus C Sommen

Petrus J Van Gerwen

Theodoor A Claasen

Hendrik J Kotmans

Christinus Johannes Van Valburg

Adaptive discrete-time filters, as used, for example, in echo cancellers responsive to input signals, more specifically speech signals, which can be modelled with an autoregressive process of the order of p, a control circuit for controlling the coefficients for adjusting a discrete-time transversal filter in accordance with an algorithm which requires the same amount of computation as the Least Mean Square (LMS) algorithm but leads to the same or better convergence results for this type of signals than the Orthogonal Projection (OP) algorithm.

Adaptive discrete-time transversal filter

A frequency-domain block-adaptive digital filter (FDAF) having a finite impulse response of length N for filtering a time-domain input signal in accordance with the overlap-save method includes window means (11) for obtaining modifications (B(p;m)) of the 2N frequency-domain weighting factors (W(p;m)) from correlation products (A(p;m)). A known FDAF of this type contains five 2N-point FFT's, two of which are used in the window means (11). By utilizing a special time-domain window function which can be implemented very efficiently in the window means (11) with the aid of a frequency-domain convolution, a FDAF of this type containing only three 2N-point FFT's is obtained whose convergence properties are comparable to those of the known FDAF containing five 2N-point FFT's.

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Eindhoven, Netherlands

Petrus C Sommen