Performance of power and bandwidth efficient modulation techniques in regenerative and conventional satellite systems

On-board satellite regeneration is an effective way of reducing distortions introduced due to a cascade of two nonlinear devices. QPSK modulation method is considered and compared to OKQPSK and MSK modulation techniques for use in both regenerative and conventional satellite systems. As an illustration, simulation results for a 120 Mb/s system having cascaded nonlinearities, which include both AM/AM and AM/PM conversions, are presented for both regenerative and conventional translating systems. The filters in the system are chosen to meet the Intelsat V specifications. QPSK outperforms OKQPSK and MSK in both regenerative and conventional systems. By using regeneration a gain of 2 to 5 dB can be achieved depending on the modulation method. It is also shown that the gain to be realized by using regeneration is significantly influenced by the group delay characteristics of the filt