A Self-Calibration SCPA With Storage Capacitor Array Supporting 64-/256-/1024-QAM

Abstract

This article presents a digital polar Doherty switched-capacitor power amplifier (SCPA) using on-chip self-calibration technique with storage capacitor array (SCA) to compensate the amplitude modulation (AM)-phase modulation (PM) distortion automatically for high data-rate signals. Such a self-calibration technique detects the AM-PM distortion at output and generates the related phase compensation in PM signals. The SCA is proposed to store control voltages of phase shifter for different amplitude code and decrease the settle time for high data-rate, which achieves fast locking of the calibration loop. Based on the proposed self-calibration with SCA, a polar Doherty SCPA is designed and fabricated in conventional 40-nm CMOS technology. This chip achieves 28.9-dBm peak output power (AP sat) and 43.9% peak drain efficiency (DE) at 1.8 GHz. It supports 100-MHz 64-QAM/10-MHz 1024-QAM signal with 22.6-/21.3-dBm average output power and 33.9%/32.1% average DE without digital pre-distortion (DPD).