Digital filters for high performance audio delta-sigma analog-to-digital and digital-to-analog conversions

A multi-stage decimation filter is described which consists of comb filters and a single-stage finite impulse response (FIR) filter. A multi-rate comb filter structure is used to reduce the data path width. A multi-stage interpolation filter consists of a half-band filter and a short FIR filter. The short FIR filter is designed with a nonlinear phase to realize an overall constant group delay-signal path. The coefficients of the FIR filters are optimally quantized to canonical-signed-digit form to realize multiplier-free (shift-and-add) filter implementations