K-band GaAs Doherty Power Amplifiers for microwave backhaul

This paper presents the design and characterization of two Doherty power amplifiers for K-band applications implemented with Qorvo's 150 nm GaAs pHEMT technology. A 1 W module is developed first, and a 2 W amplifier is then obtained by combining on-chip two identical Doherty modules. The complete characterization of the two amplifiers demonstrates that the design approach, based on a matching combiner rather than a 50 Ω combiner, leads to very good combining efficiency with a relatively compact layout. The combined amplifier achieves, in the 23.2 GHz-25.2 GHz range, an output power in excess of 32 dBm, a remarkably high power for a GaAs Doherty MMIC amplifier at these frequencies. The small-signal gain is around 10 dB, while the power-added efficiency is higher than 24% and 19% at maximum power and at 6 dB back-off, respectively, over the whole frequency range.