Combined Linear and Δ-Modulated Switched-Mode PA Supply Modulator for Polar Transmitters

Abstract

A combined linear and Δ-modulated switched-mode PA supply modulator for polar transmitters is designed in a 0.25μm CMOS process. The modulator follows the input envelope and achieves 20dB output DR, a maximum efficiency of 75.5%, and 75dB SNDR for envelope signals up to 4MHz occupied RF BW. For a 1625kb/s 8PSK RF input at 900MHz, polar modulation of a GSM-900 PA provides 10dB ACPR improvement.