Recursive bitstream conversion

The author describes an algorithm for sample-rate conversion. Particular emphasis is placed on application of the algorithm for the conversion of the 1-b format as produced by a sigma-delta modulator into the PCM format. The algorithm permits subsampling before the major filtering operation and is therefore interesting for high-frequency applications such as A/D conversion of video signals. The algorithm facilitates implementations in which hardware for the decimation and frequency correction functions is shared. As bandwidth limitation is the only requirement for the associated filter, further hardware reduction can be obtained by choosing single poles at very specific locations. The resulting hardware efficiency is illustrated by the layout of a CMOS circuit for a practical example