Serial MSK-Type Detection of Partial Response Continuous Phase Modulation

Abstract

Partial response continuous phase modulation (CPM) schemes have a high spectrum utilization and also a high immunity to nonlinear distortion, since they have a constant envelope. Schemes with high power efficiency can also be designed when they are coherently detected with a Viterbi detector. These schemes are sometimes complex, however. In this paper two minimum-shift-keyed (MSK)type receivers are studied. The MSK-type receiver can be implemented as a serial receiver and as a parallel receiver. Both receivers are useful for binary modulation schemes with modulation index <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">h = 1/2</tex> . Only coherent detection of signals transmitted over an additive white Gaussian noise channel is considered. The serial receiver can be implemented with only two filters and simple decision logic. The decisions are made serially in one decision eye pattern. Two types of receiver filters are considered. Error probability results are presented for the receiver, both with and without phase and timing errors present in the receiver. It is shown that, assuming perfect phase and time synchronization, the serial and parallel receivers have equal performances. The advantages of the serial receiver over the parallel receiver are the same for partial response continuous phase modulation as for classical MSK; i.e., both in implementation aspects and in the reduced sensitivity to phase errors.