Modulation circuit for a digital radio communications apparatus using a phase shifted DQPSK modulation system

摘要

A modulation circuit includes a mapping position detector as well as a circuit for differentially phase coding a plurality of separated data streams. The differentially phase coding circuit is adapted to differentially phase code the plurality of data streams for each pulse time and generate a coded signal containing amplitude information. The mapping position detector detects the phase mapping position of the coded signal based on the amplitude information in the coded signal which is output from the differentially phase coding circuit. Information representing the detected phase mapping position is supplied to the differentially phase coding circuit so as to achieve a differential phase coding at a pulse time following one pulse time.