Quadrature frequency/phase modulation
S. Fleisher, Shouxing Qu · IEEE Transactions on Communications · 1995
A digital modulation method based on quadrature-carrier multiplexing of two N-dimensional biorthogonal signal sets is proposed. An embodiment of the proposed method referred to as quadrature frequency/phase modulation (QFPM), and its continuous phase modification CP QFPM, are described. QFPM results when two NFSK/2PSK (combined frequency and phase shift keying) signals are quadrature-carrier multiplexed. The power efficiency of QFPM and CP QFPM on the AWGN (additive white Gaussian noise) channel is always superior when compared to that of quadrature-amplitude modulation (QAM), and their bandwidth efficiency is demonstrated to be under certain conditions comparable or better than that of QAM. Both schemes possess a self-synchronization capability. The demonstrated performance characteristics of QFPM and CP QFPM suggest that they may be competitive with respect to QAM on channels where little or no filtering is desired.>