An Asymmetrical Single-stage GaN MMIC DPA at 25 GHz Implementing Dynamic Input Power Division for Enhanced PAE at 7.6 dB OBO

This paper presents an asymmetric single-stage Doherty power amplifier (DPA) in MMIC form using OMMIC GaN transistors operating at 25 GHz. The DPA implements a dynamic input power division technique in contrast with the more conventional fixed input power division. The technique mentioned above splits the input power by sending most of the power to the main PA when the peak PA is not conducting. Therefore, the power sent to the peak PA gradually increases after it reaches a certain input power level and starts conducting. This behavior is achieved by taking advantage of the non-linear behavior that characterizes the gate capacitance of a transistor in class C operation. As a result, the input impedance of the peak PA will be matched appropriately for saturation. However, it will show a higher real-valued impedance at power levels below back-off (BO) operation. This will have a substantial positive impact on the PAE and small-signal gain degradation at BO that would occur if fixed input power division was to be used. The DPA reaches a maximum output power of 33.8 dBm at a PAE of 28% and efficiency of 22% for 7.6dB OBO, keeping a level of PAE over 16% over the 7.6dB to maximum output power range.