A 90W High-Efficiency Four-Way Doherty Power Amplifier with 37.8% Fractional Bandwidth over a 15 dB Power Back-Off Range

This work presents the synthesis, design, and implementation of a new four-way Doherty power amplifier with an easy-to-implement <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$2 \times 2$</tex> output combiner. By careful selection of the drive profiles of the main and three peaking amplifiers, the proposed Doherty amplifier achieves smooth RF output power and efficiency over a very large fractional bandwidth and power back-off range. For validation purposes, a 90 W GaN four-way Doherty amplifier has been realized for the 0.9 GHz band. The measurement results show more than 49.5 dBm saturated output power over a 37.8 % relative bandwidth with drain efficiency ranging from 54.0 % to 59.3 %. At 15 dB power back-off, the efficiency is maintained within the range of 41.3 % to 51.1 %.