A 35–100GHz Continuous Mode Coupler Balun Doherty Power Amplifier with Differential Complex Neutralization in 250nm InP

This paper presents a 35-100GHz continuous mode coupler balun Doherty PA (CCDPA) in a 250nm InP process for 5G & Beyond wireless applications. The CCDPA employs a new active load modulation network using two coupler baluns in series connection, which, together with Main/Auxiliary (Aux) PA role exchange, achieves Doherty-like back-off efficiency enhancement over a 3:1 bandwidth. Distinct from the LMBA PA with 90° coupler, our CCDPA and its coupler balun active modulation network offers several key advantages including differential operation, equal Main/Aux PA weighting, and no inherent early gain compression. Each CCDPA Main/Aux path consists of a two-stage common emitter (CE) PA for optimal power gain and efficiency. Moreover, at the power device level, a novel differential complex neutralization technique is used to achieve broadband double-peak gain/reverse isolation improvement. At 60GHz, the reported CCDPA achieves 27.3% peak PAE with 21.5dBm Psat, 22.9% PAE at 19.3dBm OP1dB, and 19.1% PAE at 15.5dBm (6dB PBO). Overall, the InP CCDPA achieves 18.9-22.6 dBm Psat, 14.7-29.3% peak PAE and 8.2-19.2% 6dB PBO PAE over 35-100GHz, showing ×1.08-×1.4/×2.16-×2.8 6dB PBO efficiency boost ratio compared to normalized ideal class-B/class-A PA.

I. Introduction

Mm-Wave wireless technologies serve as a key enabler for 5G and beyond-50 revolutions. To maximize the throughput, capacity, and frequency diversity, wireless standards mandate channels with OHz bandwidth (BW) over multiple noncontiguous mm-Wave bands. As high peak-to-average-power-ratio (PAPR) spectrally efficient modulations. e.g., OFDMs, are widely employed, system dynamic range and linearity are also critical. Moreover, to compensate for the mm-Wave path loss and enable diverse MIMOs, complex high-density arrays with high system energy efficiency are increasingly needed. These requirements pose tremendous challenges on mm-Wave frontends, in particular power amplifiers (PAs). There is a perennial quest for fundamental innovations on PA topologies [1] that can simultaneously deliver high efficiency (at both peak and back-offPBO) and high linearity over a wide BW.