A 39.5 dBm GaN Doherty Amplifier MMIC with Phase Control for Ka-band Space Applications

In this paper, a high-power multi-cell, multi-stage GaN MMIC Doherty Power Amplifier (DPA) for space applications is presented. The amplifier implements a novel approach for the Doherty output power combiner, integrating matching and load modulation in the output matching network of the main and peak PAs. To achieve high efficiency operation of the DPA at 7 dB output power back-off (OBO), an asymmetric 2.5:1 input power division ratio was realized. The DPA is operating at Ka-band between 25.5 and 27 GHz supporting two 750 MHz wide channels. Two digitally controlled phase shifters are implemented in the input of the main and peak PAs allowing on-chip phase balance of the main and peak signals. This allows for optimization of the performance across the two sub-bands. The DPA delivers a maximum saturated output power over 39.5 dBm at 24% PAE and over 17% PAE at 7 dB back-off operation.