Resistive-reactive class-X power amplifier with bandwidth beyond one octave

This article presents a resistive-reactive Class-X power amplifier (PA) with bandwidth beyond one octave. By introducing resistive component into the second-harmonic load of Class-X power amplifier, the impedance design space is expanded. The basic theory of extended Class-X PA is deduced, including impedance calculation, high-efficiency design consideration and targeted impedance trace design. An impedance overlapping region between fundamental and second-harmonic impedances with high drain efficiency is obtained, paving the way for bandwidth enhancement. For validation, the Class-X and extended Class-X theory are employed to design a broadband PA with bandwidth of 0.6-2.6 GHz (125%), drain efficiency of 57%-70%, and gain of 10.2-13.2 dB.