SNR-maximizing interpolation filters for band-limited signals with quantization

As an interpolation filter for sampling rate transformation, a half-band filter with a reduced amount of computation is often used. Due to the restrictions on its amplitude characteristic, it is not possible to sufficiently reduce the quantization noise of the transition region of the filter. In this paper, the output SNR of the L-interpolator filter is analyzed with a quantized band-limited signal as the input. A design method is proposed for the linear phase FIR filter maximizing the output SNR. For the design, both the SNR maximizing design within the Type I FIR filters and one supplemented with the restriction of the L-th band filter are presented. Each design is reduced to derivation of the solution of a system of linear equations with a coefficient matrix represented analytically. The filter based on the proposed method can attain an SNR not attainable under the sacrifice of the order in the conventional filter taking into account only the passband and the stopband. (c) 2005 Wiley Periodicals, Inc.