Digital transmission system comprising a double synchronising loop

摘要

The transmission system (10) includes a receiving appts. (14) with a demodulating circuit (110) and processing circuit (120). A synchronising device (16) synchronises the carrier to estimate and compensate for synchronisation faults. The synchronising device includes a first loop (1) for phase and frequency correction and a second loop (2) for phase correction with first and second error signals produced respectively by the loops. The error signals are filtered. Their operation is controlled by a mode detector (130) by which the latched or unlatched status is determined. The second loop mixes the phase correction signal with a demodulated signal.