Circulator Load Modulated Amplifier: A Non-Reciprocal Wideband and Efficient PA Architecture

A novel power amplifier (PA) architecure, the Circulator Load Modulated Amplifier (CLMA), is presented and demonstrated. Based on a 3-port non-reciprocal combiner, the CLMA is able to modulate the load of a class-B amplifier by means of controlling the amplitude and phase of a class-C amplifier. The architecture enables broadband highly-efficient operation over a reconfigurable output power control range. As a proof of concept, a narrowband prototype PA based on GaN transistors and a commercial circulator is employed to validate the CLMA concept. It exhibits peak output power of 43.1 dBm and drain efficiency of 73% at 6-dB output power control range at a center frequency of 2.09 GHz.