| 摘要 |
A QDPSK communication receiver includes a frequency source, apparatus for translating a received QDPSK signal having inphase I and quadrature phase Q components to baseband and a baseband demodulator. For each symbol period of the baseband QDPSK signal, a signal (Idiff) representative of the inphase component of the phase different between immediately successive received symbols and signal (Qdiff) representative of quadrature phase component of the phase difference between immediately successive received symbols is formed. In order to synchronize the frequency of the receiver frequency source to carried frequency of the received QDPSK signal, a preamble interval is defined during which a sequence of identified symbols is received. The inphase difference component signals of the symbols of the preamble interval are compared with the quadrature difference component signals of the symbols of the preamble interval to generate a plurality of signals representative of a set of predetermined relationships between the inphase difference component signals and the quadrature phase difference component signals. The frequency of the receiver frequency source is adjusted responsive to the plurality of predetermined relationship signals.
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