Trellis Sigma-Delta Modulation

Abstract

Chapter seven presents a full analysis of the Trellis sigma-delta modulation algorithm. This algorithm is the first pruned look-ahead sigma-delta modulation algorithm found in literature. It is a derivative of the full look-ahead algorithm and uses concepts from Trellis (Viterbi) decoding, hence the name. In the Trellis sigma-delta modulation algorithm, at all times, a total number of 2N potential solutions (paths) are investigated, of which the most recent N symbols are different for all the solutions. The output symbol of the converter is found by tracing back any of the 2N paths L time steps. After the algorithm discussion a performance analysis is performed, which shows that the Trellis sigma-delta modulation approach results in a converter that has an improved linearity and better stability than a normal sigma-delta modulator, although the computational load is very high. Suggestions for an efficient implementation of the algorithm are provided as well.