A balanced-to-Doherty (B2D) mode-reconfigurable power amplifier (PA) is presented in this article, which is endowed with a unique capability of maintaining high linearity and high efficiency against load mismatch. The Doherty operation of this PA is based on a new Doherty PA (DPA) architecture configured from an ideal balanced amplifier, named quasi-balanced DPA (QB-DPA). This article, for the first time, analytically proves that the QB-DPA is functionally equivalent to a standard DPA. Most importantly, this new discovery enables PA reconfiguration between the Doherty and balanced modes. With the tunability implemented using a silicon-on-insulator (SOI)-based single-poledouble-throw (SPDT) switch, a reconfigurable B2D PA prototype using GaN technology is demonstrated at 3.5 GHz, exhibiting the state-of-the-art linear DPA performance in the nominal 50-Ω load condition. Specifically, the Doherty mode achieves a continuous-wave measurement efficiency of 70% and 54.5% at the maximum output power of 41.9 dBm and 6-dB power backoff, respectively. In the modulated long-term evolution (LTE) evaluation, the DPA exhibits -37-dB adjacent channel power leakage (ACPR) and 2.36% error vector magnitude (EVM) at the maximum rated power of 34.5 dBm while achieving a 42.4% efficiency. It is experimentally demonstrated that the Doherty (QB-DPA) mode is well resistant to load mismatch with high efficiency across a majority portion of the 2:1 voltage standing wave ratio (VSWR) circle, while the combination of Doherty and balanced modes can ensure a constantly linear performance of the B2D PA (e.g., 2.2%-5% of EVM) under the entire mismatch condition.
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Novel Outphasing Power Amplifiers Designed With an Analytic Generalized Doherty-Chireix Continuum Theory
An analytic theory for dual-input outphasing power amplifiers that incorporate in one unified treatment, the continuum of solutions for power combining including the Doherty and Chireix modes is presented. This unified theory developed at the current-source reference planes reveals the performance trade-off achieved by all of the possible power amplifier (PA) combiners within the continuum of solutions. Furthermore, it identifies a novel type of dual-input hybrid Chireix-Doherty PA that combines key features of the Doherty and Chireix operations such that the fundamental drain voltages applied to both the main and auxiliary transistors remain constant. This hybrid PA relies on an input outphasing angle varying with the input power level to obtain the correct load modulation behavior. A 2-GHz dual-input hybrid Chireix-Doherty PA is implemented using nonlinear embedding and experimentally evaluated to validate the theory. A drain efficiency of 61% at 9-dB backoff power and a maximum output power of about 43 dBm are obtained for continuous-wave (CW) measurements. The efficiency increases monotonously with output power unlike that of the Doherty PA used for comparison. When excited with a 20-MHz LTE signal with 9.5-dB peak-to-average power ratio (PAPR), the dual-input PA yields a 60.0% average drain efficiency and -48.1-dBc adjacent-channel power-leakage ratio (ACLR) after linearization.
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- Award ID(s):
- 1711278
- NSF-PAR ID:
- 10098207
- Date Published:
- Journal Name:
- IEEE Transactions on Circuits and Systems I: Regular Papers
- ISSN:
- 1549-8328
- Page Range / eLocation ID:
- 1 to 14
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1109/TCSI.2019.2910471
