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IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES, VOL. 54, NO. 12, DECEMBER 2006 4479 Linearity Improvement of HBT-Based Doherty Power
 

Summary: IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES, VOL. 54, NO. 12, DECEMBER 2006 4479
Linearity Improvement of HBT-Based Doherty Power
Amplifiers Based on a Simple Analytical Model
Yu Zhao, Student Member, IEEE, Andre G. Metzger, Student Member, IEEE,
Peter J. Zampardi, Senior Member, IEEE, Masaya Iwamoto, Member, IEEE, and Peter M. Asbeck, Fellow, IEEE
Abstract--A simple analytical model is proposed and shown to be
effective in predicting the nonlinear behavior of single-ended am-
plifiers, as well as Doherty amplifiers implemented with GaAs het-
erojunction bipolar transistors (HBTs) for handset applications.
The analytical model is based on linear and nonlinear components
extracted from a vertical bipolar inter-company model for Sky-
works Solutions Inc.'s InGaP/GaAs HBT devices. Equations de-
rived from the model provide insights into effects of individual
components on the gain and phase of both the single-ended and Do-
herty amplifiers. The model indicates that tuning the phase delay
inserted in front of the auxiliary power amplifier (PA) within the
Doherty can improve linearity at a high input power. The efficacy
of the model is demonstrated by experimental results in which, for
a Doherty PA with a tuned phase delay at the auxiliary PA side, the
measured gain and phase agree with the simulation results. Fur-

  

Source: Asbeck, Peter M. - Department of Electrical and Computer Engineering, University of California at San Diego

 

Collections: Engineering