Receiver design and performance evaluation with ENCAP-4N digital modulation

The authors examine the coherent detection of ENCoded-Amplitude-and-Phase (ENCAP) offset quadrature phase shift keying (OQPSK) signals with the help of both QPSK-type (MSK-type) receivers and Viterbi receivers. Numerical results are presented on the performance of parallel and serial OQPSK-type receivers as well as matched and mismatched Viterbi receivers. In some cases where compact spectra are obtained, it turns out that the OQPSK-type receivers are nearly as efficient as the optimal Viterbi receivers, even though the former are much simpler. As for sensitivity to synchronization errors, the Viterbi receivers, even if perfectly matched, are not clearly superior to the OQPSK-type receivers