An externally-synchronized coherent communication system design.

摘要

The research described within this dissertation was initiated to investigate coherent communication improvements made possible by using a carrier reference derived from a residual carrier broadcast. It develops theoretical and simulated predictions of the performance of transceivers using a residual carrier broadcast as the basis for coherent modulation and demodulation.; Coherent demodulation provides superior link performance in the form of lower bit error rate (BER) for a received signal with a given signal-to-noise-ratio (SNR). Unfortunately, it is not always possible to produce a reliable replica of the carrier signal from the information-bearing signal.; The studied approach supplies a residual carrier reference signal as a carrier synchronization reference common to both transmitter and receiver. Research shows that the common reference provides carrier synchronization and stabilizes the link carrier frequency.; The investigations performed under this research effort includes developing a model for a radio frequency (RF) link using an external reference signal, determining the effects of noise on the simulated reference signal, and comparing the simulated link performance with conventional links, which recover a carrier from the received signal. The model consists of three parts. The first part consists of a model using conventional synchronization in which the carrier is extracted from the information-bearing signal. The second part models the behavior of phase-locked loops (PLLs) when referenced to a residual carrier reference signal. The third part is a design tool for predicting the synchronization and bit error performance of a transmitter and a receiver synchronized to external residual carrier broadcast (a triad configuration). The models demonstrate that a transceiver referenced to a double-sideband residual carrier broadcast maintains synchronization at a very low received SNR.; Results of this research could be used in the development of externally-referenced wireless links for commercial and military applications. The models could serve as design aids to determine the expected performance of such systems.