High performance open-loop AM modulator designed for power control of E-GPRS polar modulated power amplifier

An E-GPRS power amplifier controller, designed in a 5 V 0.5 /spl mu/m CMOS technology, is presented. Based on an open-loop polar modulation transmitter strategy for both GMSK in GSM and 8PSK in EDGE, the power control for both ramping and modulation depth is provided from collector supply control, and critical power amplifier (PA) temperature and process variability is compensated through the use of an automated bias calibration procedure detailed herein. Leveraging the architecture's capability for removal of transmit SAW filters, removal of isolators and maintenance of critical adjacent channel power ratio (ACPR) and error vector magnitude (EVM) performance into PA output mismatched impedance environments, the controller provides excellent linearity for higher power 8PSK power, and performance of transient spectrum due to switching even when run into the battery headroom limit of the supply rail.