Performance of bandlimited QPSK, OKQPSK and MSK signals through cascaded nonlinearities

An analysis on the amplitude fluctuations, both the overall average and at the sampling instants for filtered QPSK and OKQPSK signals is presented. A wideband model and two narrowband models are used to evaluate the performance of QPSK, OKQPSK and MSK through cascaded nonlinearities and bandlimiting elements as in a typical satellite channel. Results from the wideband model show that OKQPSK performs slightly better than conventional QPSK and MSK. On the contrary, results from the two narrowband models show that conventional QPSK outperforms OKQPSK and MSK.