Design strategy for tri-band Doherty power amplifier

This paper presents design of a tri-band Doherty power amplifier operating at frequencies of 1.6 GHz, 1.9 GHz and 2.2 GHz. The circuit utilizes two 10 W GaN HEMT transistors in a symmetric Doherty power amplifier configuration. A peak drain efficiency of more than 60% is achieved in measurement at each frequency of operation. At 6 dB output power back-off, the measured drain efficiency is more than 45% at 1.6 GHz, 2.2 GHz and better than 38.2% at 1.9 GHz. In comparison to the balanced mode operation, this corresponds to an improvement of 19.7%, 10.4 % and 16.7% in the drain efficiency achieved at 1.6 GHz, 1.9 GHz and 2.2 GHz respectively. The ratio of Carrier to third order intermodulation distortion is better that 18 dBc at saturation for all three frequencies of operation.