INITIAL SYNCHRONIZING METHOD FOR DEMODULATION OF FREQUENCY PATTERN SIGNAL

摘要

PURPOSE:To ensure a stable initial synchronous lead-in, by controlling the timing of the local oscillation signal with the correlation output between the received signal and the local oscillation signal. CONSTITUTION:In case the carrier frequency is transmitted after switched to the pseudo random, the test data is transmitted first. The received signals are mixed at the receiver side with the output signals of the mark frequency pattern signal generator and the space frequency pattern signal generator. Then the regular intermediate frequency component of the intermediate frequency signals M and S obtained through the above-mentioned mixing plus the detuned intermediate frequency component are extracted through band pass filters 18-21. A mutual addition is given to the envelope curve detection signals of the frequency signals. A certain level of output emerges at the mark or space side if no synchronism is secured for the local oscillation signal. An output obtained by a correlation between the correlation characteristics of the frequency pattern and the interference wave emerges at all time to the output of the detuning frequency side. Thus a synchronous control is carried out by the level comparator 32.