Broadband Active Load-Modulation Power Amplification Using Coupled-Line Baluns: A Multifrequency Role-Exchange Coupler Doherty Amplifier Architecture

Abstract

Broadband active load-modulation power amplifiers (PAs) are effective to enable multistandard wireless communication systems with high dynamic-range wideband signals and high energy efficiency. Traditional Doherty or outphasing PA architectures support their classic active load-modulation operations but, however, exhibit limited carrier bandwidth. We propose a broadband active load-modulation PA architecture with multifrequency role-exchange coupler-based Doherty amplifier (MF-CDA) operations to cover over-an-octave bandwidth. A proof-of-concept PA has been designed and fabricated in a 45-nm RF CMOS SOI process, which achieves a peak PAE of 41.88%–19.4% with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$P_{\mathrm {sat}}$ </tex-math></inline-formula> of over 22.66–19.53 dBm from 26 to 60 GHz. The PA also achieves a 33.75%–10.2% 6-dB PBO efficiency with its best 1.8 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times $ </tex-math></inline-formula> efficiency enhancement over an ideal Class-B PA. Using a single-carrier 64-QAM signal with 0.8–3 GSym/S (4.8–18 Gb/s), the PA supports an average <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$P_{\mathrm {out}}$ </tex-math></inline-formula> of 15.8–11.3 dBm with an average PAE of 23.8%–8.5% at −23-dB rms EVM over the entire bandwidth. For a single-carrier 16-QAM signal with 1–2.5 GSym/S (4–10 Gb/s), the PA achieves an average <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$P_{\mathrm {out}}$ </tex-math></inline-formula> of 18.7–15.6 dBm with an average PAE of 34%–14.8% at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$&gt;-$ </tex-math></inline-formula> 20-dB rms EVM over the bandwidth. The PA also supports 5G NR modulation using 5G new radio (NR) FR2 200 MHz 1-CC 64-QAM signals, achieving 16.54%–5.2% average PAE at 12.25–9.34 dBm and average <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$P_{\mathrm {out}}$ </tex-math></inline-formula> with an rms EVM of −24 dB over 26–60 GHz.