AlGaN/GaN $Ka$ -Band 5-W MMIC Amplifier

A broadband Ka-band AlGaN/GaN on SiC high electron-mobility transistor monolithic-microwave integrated-circuit (MMIC) power amplifier was developed for millimeter-wave antenna applications. The 0.18-mum gate two-stage 50-Omega matched MMIC produces 13plusmn1 dB of gain from 26 to 36 GHz. At 35 GHz, the measured continuous wave (CW) saturated output power (P_out) was 4 W (5 W pulsed), indicating a CW power density of 3.3 W/mm (4.2 W/mm pulsed). The CW power-added efficiency was 23%. Across the band, the measured CW P_out was >2 W (2.5 W pulsed). While individual (or partially matched single stage) devices have been demonstrated with good output power, to the best of our knowledge, this is the first report of a 10-GHz-bandwidth Ka-band GaN MMIC with high output power and gain. A unique aspect of the design, contributing to the wide bandwidth, is the use of positive feedback in the first stage to increase the gain. RF power stress test and detailed investigation of the channel temperature effect are presented. A preliminary RF power stress test indicates a lifetime of 1000 h at 191 degC channel temperature, and elevated temperature operation indicates that P_out decreases by 0.013 dB/degC