| 摘要 |
PURPOSE:To reproduce easily a carrier wave for synchronizing wave detection of a received multi-value QAM (quadrature amplitude modulation) signal at the reception side, by providing a phase control circuit which outputs the signal component produced by a leakage carrier wave contained in a synchronizing wave detection output signal of said QAM signal in the form of a phase control signal. CONSTITUTION:A received multivalue QAM signal is branched by a hydrid circuit 21 and applied to syncrhonizing wave detectors 22 and 23. The output signals fed from a voltage control oscillator 33 are supplied to those detectors 22 and 23 with 90 deg. phase to each other via a 90 deg. hybrid circuit 34. In other words, the QAM signal receives the synchronizing wave detection by using the output signal of the oscillator 33 as a reproduction carrier wave. Then a signal of a level corresponding to both the frequency and phase differences between a leakage carrier wave and a reproduction carrier wave appears to the multi-value data DQ of a channel Q of the output signal of the detector 23. A phase synchronizing circuit is designed so that the above-mentioned signal is set at zero, and the output signal phase, i.e., the reproduction carrier wave phase is controlled. Thus it is possible to obtain synchronization between the phase of the reproduction carrier wave and that of the leakage carrier wave. |
