New Modulation Techniques for Low-Cost Power and Bandwidth Efficient Satellite Earth Stations

New power and bandwidth efficient modulation techniques, named intersymbol interference and jitter-free (IJF)-QPSK and IJF-OQPSK, are presented. The properties of the IJF-QPSK and IJF-OQPSK signals in linear and nonlinear earth-station-satellite systems are studied. A finite-state Markov chain model is used to calculate power spectra of hard-limited IJF-QPSK and IJF-OQPSK. The model provides insights into the spectral spreading action of the ideal hard-limiter on the IJF-QPSK and IJF-OQPSK signals. Experimental, simulation, and theoretical results are in good agreement. The results indicate that the IJF-OQPSK modulated signal exhibits much less spectrum spreading than QPSK, OQPSK, and MSK. The error probability (P_e) performance of IJF-QPSK and IJF-OQPSK in an additive white Gaussian noise and adjacent-channel interference environment is evaluated. The results show that the P_e performance of the IJF-OQPSK is superior to that of QPSK, OQPSK, and MSK is narrow-band nonlinear channels.