System architecture of an all-digital GHz transmitter using pulse-width/position-modulation for switching-mode PAs

This paper presents a novel concept for direct-pulse-width/position-modulation (PWPM) in an all-digital transmitter by using a parallel baseband PWPM and high speed digital up-conversion. By parallel calculation and subsequent serialization of the digital PWPM signal carrier frequencies above 1 GHz become feasible. PWPM enables the usage of highly efficient switching-mode power amplifiers (SMPA) and direct control of the output power. Because PWPM modulator can be completely implemented in the digital, time discrete domain, all analogue baseband blocks can be dropped and replaced by reconfigurable digital blocks. The only remaining mixed-signal and analogue blocks are the multiplexer and the power amplifier. Requirements on the digital and mixed-signal blocks are discussed. Feasibility of the concept is demonstrated by system and circuit simulations showing the possibility of using digital PWPM in wireless applications.