A Triple-Power-Mode Digital Polar CMOS RF Power Amplifier With LO Duty Cycle Control

Abstract

A triple-power-mode digital polar CMOS power amplifier (DPA) with a high dynamic range is presented. The triple-power-mode to enhance the efficiency when operating under back-off power is facilitated by the combination of a switched output transformer to change the load impedance and a reduced duty cycle of the LO input signal of the DPA for additional back-off power. This static power-mode method for the low-power region can be used with a DPA which has a high dynamic range in conjunction with a digitally controlled bias generator. An improvement in the PAE from 14.5% to 28.7% is achieved at a back-off power of 6.5 dB from a peak output power of 21.54 dBm at 1.7 GHz. A digital transmit power control (TPC) range of 68.2 dB for WCDMA is realized without any external components.