A High Gain Ka-Band Asymmetrical GaAs Doherty Power Amplifier MMIC for 5G Applications

In this paper, a 3-stage, Ka-Band, asymmetrical Doherty Power Amplifier (DPA) MMIC using 0.15-mu m depletion mode (D-mode) Gallium Arsenide (GaAs) pHEMT is presented. In order to increase operation bandwidth, the quarter-wavelength (lambda/4) transmission line behind main amplifier is eliminated and the output matching network is optimized for both back-off and peak efficiency. A 20-ohm Wilkinson power divider is used behind 1st stage so that the input impedance of the power divider can be easily transformed to the load impedance that the device at 1st stage must see. The fabricated DPA exhibits a measured output power of 27-27.5 dBm with a peak power added-efficiency (PAE) of 37%-39% in the frequency band of 27.25-29.75 GHz. The PAE at 6 dB and 7dB output power back-off are obtained as 25%-29% and 22%-28% respectively. Additionally, the large signal gain larger than 18 dB is obtained in the band of operation.