Demodulation circuit for phase-keyed digital signals - uses coherent and phase-difference demodulators to separate start pulses

摘要

The demodulation system, for phase-keyed digital signals, prevents the derivation of correlation peaks being affected by the long build up times that can occur when obtaining the carrier in coherent demodulation circuits. The likelihood of error is consequently reduced and the drop-out rate of start pulses decreased. The start pulse and the digital signals are separated by passing them to a coherent demodulator (KD) and to a phase difference demodulator. The phase difference demodulator's output is fed to a correlation receiver (KE1) to obtain in the start pulse.