Discrete-time RF phase and pulse width modulation for power efficient switch-mode transmitter

Abstract

Discrete-time RF pulse width modulation is mathematically analyzed. From the analysis a recipy for the generation of amplitude modulated RF signals by means of pulse-width modulation is derived. Furthermore a suitable fully digital polar phase and pulse width modulator architecture for switch-mode wireless transmitters is proposed. A system with 8 discrete pulse widths rsp. 16 phases at 2 GHz is modelled and simulated in Matlab/Simulink. It exhibits an SFDR of better than -67 dBc and EVM better than 1.8% with an 8 MSps 8-QAM test signal.