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A Dual-Band Outphasing Power Amplifier Based on Noncommensurate Transmission Line Concept | IEEE Journals & Magazine | IEEE Xplore

A Dual-Band Outphasing Power Amplifier Based on Noncommensurate Transmission Line Concept


Abstract:

This article proposes a design methodology of dual-band outphasing power amplifier (OPA) based on two noncommensurate transmission lines (NCTLs). The devised NCTLs are us...Show More

Abstract:

This article proposes a design methodology of dual-band outphasing power amplifier (OPA) based on two noncommensurate transmission lines (NCTLs). The devised NCTLs are used to replace the imperative reactance compensation and impedance matching networks in a conventional design. In virtue of this, the overall complexity of the combiner can be greatly reduced without sacrificing the load modulation effect. To support operations at two distinct frequencies, the conceptual NCTLs are further realized using two dual-band stub-loaded transmission lines. Comprehensive theoretical analysis is given to describe the proposed scheme and to illustrate how the electrical parameters of essential elements are determined. As a proof of concept, an OPA prototype operating at 2.6 and 3.5 GHz is fabricated. The implemented PA based on two 10-W GaN high electron mobility transistor (HEMTs) achieves 44.8 and 44.2-dBm maximum output power, and 74.5% and 62.1% peak drain efficiencies under continuous wave excitation at these two independent frequencies. At 6-dB output back-off points, the corresponding efficiencies reach 63.8% and 54.9%, respectively.
Published in: IEEE Transactions on Microwave Theory and Techniques ( Volume: 68, Issue: 7, July 2020)
Page(s): 3079 - 3089
Date of Publication: 02 June 2020

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I. Introduction

Power amplifier (PA), a key component in a transmitter, is in the process of rapid development because of the quick advancements of wireless techniques nowadays. For instance, communication schemes such as long-term evolution advanced (LTE-A) and the upcoming 5G generally rely on complex modulations that have very high peak-to-average power ratios (PAPRs). PAs are therefore required to have high efficiency at the back-off region. Because of this, load-modulated PA types, represented by Doherty and outphasing, are becoming more and more popular recently [1]–[5]. At the same time, solutions for large data throughput, such as channel bandwidth expansion and carrier aggregation, put forward increased requirement on PA bandwidth. Besides, the coexistence of old and new radio standards significantly encourages transmitters that can support wideband or multiband operation to increase hardware configurability and save system cost. Driven by these factors, various wide-band/multiband load modulated PAs have been developed in recent years [6]–[11]. In particular, significant progress has be done to the Doherty PA, for which a fractional bandwidth over one octave or triple-band operation have even become possible [10], [11].

References

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