The Correction of Phase Error for MA-SOQPSK Modulation

Multiple amplitude shaped offset quadrature phase-shift keying (MA-SOQPSK) modulation based on multiple nonlinear power amplifiers (NLPAs) provides both high power-added efficiency and spectrum efficiency. However, the phase misalignment between the different branches of MA-SOQPSK signal in the process of the modulation can significantly degrade the bit-error-rate (BER) performance. A novel scheme of correcting this phase error is proposed in this paper, which contains a phase lock loop (PLL) in the modulation terminal. Theoretical estimation and simulation on the variance of the phase error are also given to validate our method. The BER simulation result shows that our scheme improves the performance more than 3 dB at 10"3, and the improvement becomes more distinct as the SNR.