A novel DCT-based prefilter structure for efficient digital filter design

Abstract

In this paper, we present a novel prefilter structure for FIR digital filter design based on the recursive discrete cosine transform (RDCT) filter bank. The proposed prefilter structure is suitable for designing the lowpass, bandpass and highpass digital filters simultaneously. In the lowpass case, the proposed prefilter structure can be simplified to the recursive running sum (RRS) section. In the bandpass and highpass cases, implementing the new prefilter only needs two multipliers and five adders regardless of the filter length and center frequency. Compared with the conventional equiripple design approach, the proposed prefilter-equalizer cascade exhibits approximately the same sensitivity to coefficient quantization. In addition, the new structure can reduce the roundoff noise and provide significant savings in the number of multipliers and adders at the expense of slightly larger filter length.