Digital demodulator for pi/4 - QPSK signals

摘要

The received pi/4 - QPSK signal (r) is converted (101) to N baseband signals, in comparison to an N - phase clock (clk). After differential decoding (102,103), a decision error (ea) is calculated (112) for each of the N baseband signals (p3). The squared errors are integrated over a time period dependent upon a frame signal (f), and the clock phase giving the minimum squared error is found. The baseband signal which corresponds to this clock phase is then chosen as correct.