High-Efficiency WCDMA Envelope Tracking Base-Station Amplifier Implemented With GaAs HVHBTs |
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Authors: | Jinseong Jeong Kimball D.F. Myoungbo Kwak Draxler P. Chin Hsia Steinbeiser C. Landon T. Krutko O. Larson L.E. Asbeck P.M. |
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Affiliation: | Dept. of Electr. & Comput. Eng., Univ. of California at San Diego, La Jolla, MD, USA; |
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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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