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

Abstract

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 1$^{st}$ stage so that the input impedance of the power divider can be easily transformed to the load impedance that the device at 1$^{st}$ 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.