| 摘要 |
PURPOSE:To attain stable synchronization by extracting a phase error voltage at the input period only of a burst signal, switching a loop filter at a fixed phase carrier period added to the head of the burst signal and at other periods so as to control a voltage controlled oscillator. CONSTITUTION:A burst QPSK signal is inputted to detectors 1, 2, a switch 8 is closed only at a period (T=T1+T2) when a bust signal is inputted and a phase error voltage obtained by the burst signal only is fed to low pass filters 9, 10. A switch 11 selects an output of the low pass filter 9 at the head T1 of the burst signal. The cut-off frequency of the low pass filter 9 is set so that the synchronizing lock time of the loop is finished within the period T1 and the synchronization is ensured during the period. Further, the switch 11 selects the low pass filter 10 at a period (T2+T3) other than the period T1.
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