Abstract: A programmable signal decoder processes incoming signals using any one of several predefined decoding schemes. The signal decoder is programmed to perform the desired decoding operations by downloading configuration data representative of the decoding scheme from a data memory to programmable logic in the signal decoder. Programmable metric tables provide set mapping. A generic four-level decoder structure includes two levels that are programmable Viterbi decoders, one level that is a Wagner decoder and another level that provides free bit selection operations. The four levels are combined, as needed, to implement two-dimensional, four-dimensional, multi-level and other coded modulation formats.

Abstract: A simplified symbol lock detector which uses T/2 spaced signal samples in conjunction with an interpolator to approximate the T/4 shifted signal samples used by conventional symbol lock detectors. The approximated T/4 shifted signal samples are processed by a phase detector prior to input to a threshold detector which indicates proper symbol lock if the lock signal exceeds a predetermined threshold.