A Polar Doherty SCPA with 4.4°AM-PM Distortion Using On-Chip Self-Calibration Supporting 64-/256-/1024-QAM

Abstract

In this paper, an efficient switched-capacitor power amplifier (SCPA) with high linearity using on-chip self-calibration technique is proposed. The inherent AM-PM distortion in digital power amplifier (DPA) is decreased by the proposed self-calibration technique without any pre-distortion. Meanwhile, to improve the modulation bandwidth, a storage capacitor array (SCA) is introduced to decrease the settle-time of the calibration loop for transition among various baseband signals. The proposed polar Doherty SCPA is implemented in conventional 40-nm CMOS technology. It operates in 1.4-2.8 GHz with peak output power of 28.9 dBm, peak drain efficiency (DE) of 43.9%, peak system efficiency (SE) of 37.2%, and AM-PM distortion of 4.4°at 1.8 GHz. It supports 100 MHz 64-QAM signal (i.e., 22.6 dBm average output power, 4.87% EVM, and 33.9% average DE) and 10 MHz 1024-QAM signal (i.e., 21.3 dBm average output power, 1.77% EVM, and 32.1 % average DE) without any pre-distortion.