Pseudo-coherent phase shift keyed demodulator

A PSK (phase-shift keyed) demodulator that combines many of the advantages of coherent and noncoherent demodulators is described. It has the structure of a typical coherent demodulator, but it has no carrier recovery function, using instead an instantaneous estimate of the carrier; hence the name pseudo-coherent is used. It results in a differential phase shift directly out of the detector. The carrier estimates can also be used as input to a carrier recovery routine if coherent demodulation is desired. Since the demodulator structure is similar to coherent demodulators, a recovered coherent carrier could be switched in to replace the estimates of the carrier. In this way, the estimates of the carrier could be used to provide demodulated data immediately, and after the carrier recovery circuit has converged to a true coherent carrier, the same structure could be used with the coherent carrier to realize the slightly better performance of a true coherent demodulator. Both the mathematical and the functional implementation descriptions of the demodulator are given. A few implementation results based on the Bell 212 modem standard are presented