A 42–46.4% PAE continuous class-F power amplifier with Cgd neutralization at 26–34 GHz in 65 nm CMOS for 5G applications

This paper presents a wideband high efficiency continuous class-F (CCF) power amplifier (PA) at mm-Wave frequencies for the first time. A tuned load with a high-order harmonic resonance network is used to shape the current and voltage waveforms for the proposed CCF CMOS PA. Further, a transformer with a tunable coupling-coefficient (k_tune) is incorporated in the tuned load network to address the detrimental feedback effect caused by the increased transistor gate-drain capacitance (C_gd) in deep submicron CMOS technology. This technique allows precise neutralization of C_gd, reducing undesirable influence on the tuned load, and maximizing power-efficiency and stability. The CCF PA prototype, implemented in 65 nm CMOS exhibits more than 42% power added efficiency (PAE) over 8 GHz bandwidth (26-34 GHz), while delivering saturated output power (P_sat) of 14.75 dBm at 30 GHz. This design presents one of the highest reported PAEs among mm-Wave CMOS PAs, achieving 46.4% peak PAE at 29 GHz.

I. Introduction

With the recent escalation of interest in next-generation wireless technologies (e.g., 5G, E-band and WiGig), implementation of highly efficient mm-Wave transceivers has become an important research topic. Design of suitable PAs for these systems is a critical obstacle due to the challenges associated with implementing wideband, highly efficient PAs at mm-Wave frequencies. Recently, tuned mm-Wave PAs have been demonstrated based on class-E [1]–[2] and inverse class-F [3] topologies achieving high efficiency. However the reported high efficiency is achieved only over a narrowband range.