Peak-to-average power ratio and intersymbol interference reduction by Nyquist pulse optimization

The efficiency of a power amplifier is partly determined by the peak-to-average power ratio (PAPR) of the modulated signal. Communication systems using high order QAM have large PAPR resulting in low efficiency and a high level of intermodulation distortion. In this paper, we propose a simultaneous minimization of the PAPR of the transmitted signal and the intersymbol interference (ISI) of the demodulated signal based on the optimization of the root raised cosine (RRC) filter. This is performed under spectral requirement constraints using a multivariate optimization technique. It is shown that the use of the proposed filters significantly increases the power amplifier efficiency while preserving the symbol error rate (SER) performance; 1.85 dB of power increase is typically obtained. Alternatively, they may be used to lower the spectral emissions and improve the error probability. The results were measured on a radio to obtain a 7 to 11 dB out of band signal power reduction.