Frequency Agile Monolithic GaN Doherty Power Amplifier

This paper proposes a monolithic GaN Doherty power amplifier (DPA) capable of efficiently amplifying communication signals located in multiple widely spaced wireless frequency bands. The proposed monolithic DPA incorporates a number of microelectromechanical systems switches which were used to mitigate the variation of the DPA circuit parameters within the operating frequency. A systematic design methodology was used to optimize the size and complexity of the frequency agile DPA thus locating the reconfigurability out of the combining network so that this latter can be kept off-chip. A monolithic DPA was designed and fabricated using the Canadian Photonics Fabrication Centre GaN500 monolithic microwave integrated circuit (MMIC) process (0.5 um gate length) which was operated at 1.7GHz, 2.14GHz and 2.6GHz. The preliminary measurement results demonstrated drain efficiency higher than 50% for power levels up to 6dB back-off from the peak output power.