A hybrid amplitude/time encoding scheme for enhancing coding efficiency and dynamic range in digitally modulated power amplifiers

Digitally modulated power amplifiers (DMPA) are a promising architecture for practical and highly efficient software-defined radio transmitters. Signal encoding schemes for DMPAs have primarily focused either on amplitude or time domain encoding, neither of which can simultaneously provide high coding efficiency, high dynamic range and low design complexity. In this paper, we propose, analyze and evaluate a new hybrid amplitude/time signal encoding scheme that significantly improves the coding efficiency and dynamic range of DMPAs without significantly increasing design complexity. The proposed hybrid amplitude/time encoding scheme combines both the amplitude domain and the time domain to optimally encode information. Evaluation results show that hybrid amplitude/time encoding yields a 35% increase in the average coding efficiency with respect to conventional time encoding, and is only 6.7% lower than peak efficiency when applied to a Wireless Local Area Network signal with a peak to average power ratio equal to 9.9 dB. A new DMPA architecture, based on the proposed hybrid encoding, is also proposed.