High-Efficiency Wilkinson-Power-Combining Class-EF Amplifier with Lumped-Element Load Network

This paper presents a design strategy to incorporate the load network of Class-EF power amplifier (PA) into a complex-impedance-terminated Wilkinson power combiner (WPC) in order to reduce the circuit complexity and footprint. To further reduce the circuit footprint, the WPC and the Class-EF PA's load network are designed using lumped elements as opposed to transmission lines typically employed in the classical designs. The proposed circuit provides an impedance matching from 50 Ω to a complex impedance at the fundamental frequency and a short-circuit termination at the second harmonic. The new topology exhibits a band-pass frequency response instead of low/high-pass as in the conventional WPCs, thus enabling suppression of unwanted signals at low and high frequencies. Closed-form design equations, derived using even/odd mode analysis, are given along with a design example. Driven by a 3-GHz continuous-wave input signal, the proposed PA delivers 41.5-dBm output power with DC-to-RF efficiency of 83.6% at 3.9-dB compressed gain of 15.2 dB.