A 10.8-GHz GaN MMIC Load-Modulated Amplifier

This work presents a 10.8-GHz load-modulated MMIC power amplifier designed in the 0.25 µm GaN-on-SiC Cree Wolfspeed process. The carrier amplifier has a single stage and is biased in class-AB, while the peaking path is designed as a two-stage amplifier. The output power at saturation is 35.5 dBm with 7.6 dB of gain and PAE of 38%. At 7-dB output power backoff, the PAE remains above 26%. The combiner network is synthesised with a black-box method constrained to exhibit Doherty amplifier behaviour. The disagreement between measurements and simulations is explained in part through an analysis of the interstage matching network using scattering parameters renormalised to complex terminations.