Demodulated radio signals

摘要

A received and demodulated multi-level signal (32) is corrected for D.C. offset by a feedback loop (34) which applies a correction signal (38) to the multi-level signal (32). Initial coarse correction is provided by feeding the corrected signal (42) into the feedback loop where a low pass filter (36) averages the corrected signal over time and detects departure from zero of this time-averaged signal. After initial coarse correction, finer correction of D.C. offset is provided in a data-aided mode in which detected data values (46) are fed into the feedback loop (34). The method achieves D.C. offset correction without the need to know anything about the data pattern of the received signal (32).