Harmonic-Injection Class-EM/Fn Power Amplifier With Finite DC-Feed Inductance and Isolation Circuit

This article presents the analysis and design of a Class-EM/Fn power amplifier (PA). The high peak switch voltage factor of the classical Class-EM PA is reduced by 27.3% through the adoption of the Class-F⁻¹ third-harmonic termination on the main circuit, resulting in a novel topology called the Class-EM/Fn. The adoption of a finite dc-feed inductance enables the introduction of the design parameter k, which can be exploited to extend the maximum operating frequency of the PA. The idealized voltage and current waveforms of the PA show that the main circuit fulfills not only zero voltage switching (ZVS) and zero voltage derivative switching (ZVDS) conditions as in the Class-E but also zero-current switching (ZCS) and zero-current derivative switching (ZCDS) conditions as in the Class-E⁻¹, thus minimizing power dissipation during OFF-to-ON and ON-to-OFF transitions. The load-network parameters of the main and auxiliary circuits are derived, and harmonic-balance simulations are performed to confirm the analytical results. A Class-EM/F3,5 PA employing a transmission-line load network was designed and implemented using GaN HEMTs. The constructed Class-EM/F3,5 PA delivered a drain efficiency of 83%, a power-added efficiency of 76%, and an output power of 42.3 dBm at 1.8 GHz.