Cyclic spectral analysis of continuous-phase modulated signals

Continuous-phase modulated (CPM) signals play a prominent role in modern co mmunication systems due to their desirable constant-modulus property and th e ability to control their power and bandwidth efficiencies. Popular CPM si gnals include the classical minimum-shift keyed (MSK) signal, the LREC fami ly of signals also known as continuous-phase frequency-shift-keyed (CPFSK) signals, and Gaussian MSK, which is used in state-of-the-art GSM and PCS mo bile communication systems. CPM signals, Like virtually all man-made commun ication signals, are known to exhibit cyclostationarity, which implies that their probabilistic parameters, such as mean, second moment, and higher or der cumulants, are almost-periodic functions of time, In this paper, a nove l representation of CPM signals as a sum of PAM signals is presented for bo th integer and noninteger modulation index cases. Then, the Nth-order cyclo stationarity properties of binary CPM signals are derived in terms of Nth-o rder temporal and spectral moment and cumulant functions. Moreover, the cas e of M-ary CPM signals is briefly addressed. The results are illustrated wi th simulations involving MSK, LREC, and GMSK signals.