Unbalanced Power Amplifier: An Architecture for Broadband Back-Off Efficiency Enhancement

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Title: Unbalanced Power Amplifier: An Architecture for Broadband Back-Off Efficiency Enhancement
Authors: Nikandish, GholamrezaStaszewski, Robert BogdanZhu, Anding
Permanent link: http://hdl.handle.net/10197/12024
Date: Feb-2021
Online since: 2021-03-10T17:09:12Z
Abstract: In this article, we present a new broadband power amplifier (PA) architecture with a back-off efficiency enhancement that supports very wide modulation bandwidths. The unbalanced PA is composed of two cooperating sub-PAs using the Lange couplers as input power splitter and output power combiner. The PA operation is controlled by the transistors' width ratio and coupling coefficients of the Lange couplers. The output power back-off (OPBO) level is given by the transistors' width ratio and coupling coefficient of the output coupler, while the maximum efficiency is achieved at the back-off point. These features provide more design flexibility compared with the conventional Doherty PA, where the OPBO can be set only by the transistors' width ratio, and the maximum efficiency is achieved at the peak power. Using broadband harmonic matching networks, the main and auxiliary sub-PAs operate in the continuous mode to improve efficiency over a broad bandwidth. A fully integrated unbalanced PA, implemented in a 250-nm GaN-on-SiC process, achieves 32.2-34.3-dBm output power, 27%-37% efficiency at peak power, and 27%-40% at 5-6-dB back-off, across 4.5-6.5 GHz. The PA provides 3.7/4.5% (-28.6/-26.9 dB) rms error vector magnitude (EVMrms) and 30% average efficiency for a 256-QAM signal with 100-/200-MHz bandwidth, 7.2-dB PAPR, and 25.5-dBm average output power, without using any predistortion.
Funding Details: Science Foundation Ireland
Funding Details: Trinity College Dublin (TCD)
Type of material: Journal Article
Publisher: IEEE
Journal: IEEE Journal of Solid-State Circuits
Volume: 56
Issue: 2
Start page: 367
End page: 381
Copyright (published version): 2020 IEEE
Keywords: Back-offBalanced amplifierBroadband circuitCoupler
DOI: 10.1109/jssc.2020.3014244
Language: en
Status of Item: Peer reviewed
ISSN: 0018-9200
This item is made available under a Creative Commons License: https://creativecommons.org/licenses/by-nc-nd/3.0/ie/
Appears in Collections:Electrical and Electronic Engineering Research Collection

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