Wideband High‐Efficiency Power Amplifier Using a Novel Filtering Impedance Transformer

ABSTRACT

This article introduces a design strategy for a class of broadband high efficiency power amplifier (PA) utilizing a novel bandpass filtering transformer. For fundamental impedance matching, the novel bandpass filtering transformer consisting of a triple‐mode cross‐shaped resonator is used to achieve high selectivity and harmonic suppression. With the advantage of the filtering characteristic, the second harmonic impedance can be controlled at the edge of the Smith chart, placing it within the high‐efficiency region of PA. This approach not only provides small‐signal gain response with sharp rejection characteristic but also achieves high efficiency in large‐signal simulation. For verification, a wideband filtering PA operating at 3–4 GHz is implemented and measured. The measured drain efficiency (DE), output power, and gain of the fabricated PA are 68.6%–81.2%, 40–40.1 dBm, and 11.1–12 dB, respectively.