Digital signal receiver having a dual bandwidth tracking loop

摘要

A DPSK digital signal receiver is disclosed that has a dual bandwidth offset Costas loop that is switchable from an acquire bandwidth to a narrower tracking bandwidth in response to detection of a start code preceding a message signal included in the digital signal. Detection of the start signal may occur before absolute carrier lock on, which then is completed in the narrow-band tracking mode. Thus, carrier acquisition is achieved much faster than that obtained by prior art circuits requiring absolute carrier lock on before switching bandwidths.