In this paper, a systematic design of a dual-band power amplifier (PA) is presented. Using the inherent impedance matching flexibility of a Class J operating mode, we can start by relaxing the performance sensitivity and design requirements of the matching networks. Then, a novel dual-band matching network topology is devised to simultaneously present adequate source and load impedances at the fundamental and harmonic components of both targeted operating frequencies. The dual-band matching network is designed in two stages. First, a complex-to-real impedance transformation network, with harmonic control capability, is used to transform the complex impedance for class J operation to real impedance that is common to both operation frequencies. Then, a real-to-real trans-impedance transformer is synthesized using dual-band filter theory. This technique was successfully applied to design a dual-band 45W GaN Class J PA operating at 0.8GHz and 1.9GHz. The measurement results of the fabricated PA shows peak efficiencies of 74.4% at the lower band and 57.6% at the upper band.
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