A 0.9-V 36% PAE Broadband Continuous Class-F CMOS mm-Wave Power Amplifier Using Novel Current-Mode Power Combiner

Abstract

This article presents a fully integrated broadband two-stage differential millimeter-wave (mm-Wave) power amplifier (PA) based on a novel current-mode power combiner. New harmonic terminations have been proposed to obtain an increase in power-added efficiency (PAE) over a wide range of frequencies. A capacitive third harmonic termination to the drain impedance at the output stage of PA provides flexibility in choosing a lower self-resonance frequency (SRF) of the transformer in the output matching network. The freedom of choosing a lower SRF enables the utilization of lateral coupling in the transformer (output matching network), which further removes the requirement of ultrathick top metal (UTM) layer. A low-cost solution has been developed and the PA shows improved performance even without UTM. The proposed idea generalizes the load impedance terminations and reduces the technology dependence of PA design. The PA operates both in the Ka-band and the fifth-generation (5G)-FR2 band. The PA fabricated in a 40-nm CMOS process without a UTM layer occupies a core area of 0.31 mm2. The proposed PA achieves 19.1 dB of measured small-signal gain at 28 GHz, a peak power output of 15.9 dBm from 28 to 31 GHz with a peak power-added efficiency (PAE) of 36% from a supply voltage of 0.9 V. The −3-dB bandwidth of 28.3% achieved by this design is one of the highest reported bandwidths for CMOS mm-Wave PAs. For 64-quadrature amplitude modulation (QAM) 5G-new radio (5G-NR) signal input with 200-MHz bandwidth, the PA shows a measured error vector magnitude (EVM) of −27 dB at 28 GHz and the adjacent channel leakage ratio (ACLR) $\approx -32$ dBc without utilizing digital predistortion (DPD).