A Broadband Mixed-Signal CMOS Power Amplifier With a Hybrid Class-G Doherty Efficiency Enhancement Technique

Abstract

This paper presents a broadband mixed-signal CMOS power amplifier (PA) with a hybrid Class-G Doherty architecture for PA efficiency enhancement up to the deep power back-off (PBO) region. Our proposed mixed-signal linearization technique ensures the PA’s amplitude modulation (AM)–AM linearity by digital PA operation and suppresses the PA’s AM–phase modulation (PM) nonlinearity by real-time analog phase compensation. The PA is fully integrated in a standard 65 nm bulk CMOS process, and achieves a peak output power ( ${P_{{\text{out}}}}$ ) of $+ {{26}}.{{7}}\;{\text{dBm}}$ with a 40.2% peak drain efficiency (DE) at 3.71 GHz. The DE at 6 and 12 dB PBO is $1.8\times$ and $2.6 \times$ over the reference Class-B PA operation, advancing the state-of-the-art CMOS PA PBO efficiency performance. The PA 1 dB bandwidth is extended from 1.08 to 1.8 GHz by reconfiguring the phase difference between the main and auxiliary paths in the Doherty PA. In the modulation measurements with 1 MSym/s 16 QAM signals, the PA performs dynamic hybrid Class-G Doherty operation and achieves $+ {{20}}.{{8}}\;{\text{dBm}}$ peak ${P_{{\text{out}}}}$ with 28.8% DE at 3.71 GHz and $2.42\times$ efficiency enhancement at 8.1 dB PBO over Class-B operation. The real-time AM–PM linearization technique achieves 3.3 and 2.9 dB improvements on the EVM and adjacent channel leakage ratio (ACLR), respectively. The broadband Class-G Doherty operation is also demonstrated with modulated signals.