Phase-modulated DSM-PWM hybrids with pulse length restriction for switch-mode power amplifiers

This paper describes a novel concept to encode amplitude and phase information in binary waveforms for switch-mode power amplifiers (SMPAs). A combination of a phase-modulated delta-sigma modulation (DSM) and pulse-width modulation (PWM) makes it possible to adapt signal generation to the power amplifier limits. The proposed system overcomes the inherent signal quality limits of digital systems with fixed clock frequencies by applying a phase modulated clock. We demonstrate that it is possible to achieve the performance of conventional concepts at less than half of the bit rate. Simulation and measurement results are given for important figures of merit of mobile communication signals with high peak-to-average power ratio (PAPR). A proof of concept is implemented in a laboratory setting using a conventional FPGA.