A Linear and Efficient Doherty PA at 3.5 GHz

This article outlines the design procedure and presents the results of the winning power amplifier (PA) design at the PA competition held at the 2012 IEEE MTT-S International Microwave Symposium (IMS2012) and sponsored by the High-Power Microwave Components Committee (MTT]5). Traditionally, the figure of merit (FOM) employed was the maximum continuous wave (CW) power added efficiency (PAE) multiplied by a frequency weighting factor. However, this time, a major modification has been introduced to the PAE measurement: aiming to reflect linearity as well, the PAE is to be measured when producing a two-tone carrier-to-intermodulation ratio (C/I) of 30 dB [1]. In the following, it will be explained how this has seriously affected the strategy behind the choice of the PA architecture. Unlike earlier single-track PA designs, a Doherty with driver stage design was made (see Figure 1), employing Creefs CGH40006P GaN HEMT [2]. For a 30 dBc C/I, the circuit delivered 6.5 W average output power with a two-tone PAE of 59% (66% two-tone drain efficiency) at 3.5 GHz. © 2000-2012 IEEE.