High-Efficiency WCDMA Envelope Tracking Base-Station Amplifier Implemented With GaAs HVHBTs
Jinseong Jeong
Kimball, D.F.
Myoungbo Kwak
Draxler, P.
Chin Hsia
Steinbeiser, C.
Landon, T.
Krutko, O.
Larson, L.E.
Asbeck, P.M.
Dept. of Electr. & Comput. Eng., Univ. of California at San Diego, La Jolla, MD, USA;
This paper appears in: Solid-State Circuits, IEEE Journal of
Publication Date: Oct. 2009
Volume: 44,
Issue: 10
On page(s): 2629-2639
ISSN: 0018-9200
INSPEC Accession Number: 10880524
Digital Object Identifier: 10.1109/JSSC.2009.2026845
Current Version Published: 2009-09-22
Abstract
A record high-performance GaAs high-voltage HBT (HVHBT)-based WCDMA base-station power amplifier is presented, which uses an envelope tracking bias system to achieve high efficiency and linearity. A wideband envelope amplifier provides dynamic collector supply biasing to the RF stage. A digital pre-distortion technique is employed to satisfy the linearity specifications of WCDMA. The measured overall power-added efficiency reached 58% with a normalized root-mean-square (RMS) error of 2.9% and an adjacent channel leakage ratio (ACLR) of -49 dBc at 5-MHz offset at an average output power of 42 W and a gain of 10.3 dB for a single carrier WCDMA signal with 6.6-dB peak-to-average power ratio. A memory mitigation algorithm further improves the linearity, resulting in an ACLR of -70 dBc and a normalized RMS error of 0.3%. Measurements were made to quantify separately the efficiency contributions of the HVHBT-based RF stage, and of the envelope amplifier. The measurements show that the RF stage operates at collector efficiency above 85% over most of the instantaneous power range of the WCDMA signal. This remarkably high efficiency is the result of low ldquoon-resistancerdquo and low (and nearly voltage independent) output capacitance of the HVHBT.
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