PROCESS AND CIRCUIT FOR ACQUISITION OF CARRIER SYNCHRONISM IN COHERENT DEMODULATORS

A process and a circuit for the acquisition of a carrier synchronism applicable to coherent demodulators which operate with carriers modulated by phase-shift keying (PSK). A modulated signal is divided into two signals which are multiplied (2,3) by two quadrature carriers, and the resulting signals are then added together (8) and subtracted (9) from each other to obtain a plurality of signals. At least two of them are sampled with a first frequency and at least two others are sampled with another frequency which is an even multiple of the first frequency. The proposed process makes use of a simple, low-cost circuity and gives the phase-lock loop of the demodulator an added frequency characteristic which prevents false locks and ensures lock between the local carrier and the reference signal even for very large frequency variations.