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

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.