Carrier phase synchronisation for a coded PSK signal in satellite links

A technique for carrier synchronization of a digital modem is studied. The modem transmits a rate-3/4 convolutionally encoded 16-phase-shift keyed (CE16PSK) signal over a channel with additive white Gaussian noise. The carrier synchronization circuit is data aided, employing decision feedback. Two estimates of carrier phase of the received coded signal are used in the synchronization circuit. The results of computer-simulation tests are presented and used to compare the performances of the system using two phase estimators. It is shown that the carrier-phase estimate of the received coded signal can be improved significantly by combining the phase estimation process with the decoding process of the signal. With the second phase estimator (B) which makes use of a maximum likelihood decoder, half of the possible locking positions are eliminated. As a result, the loop may acquire lock at only 8 possible positions, instead of 16.link_to_subscribed_fulltex