High-power Density W-band MMIC Amplifiers using Graded-channel GaN HEMTs

We report the W-band amplifier performance of graded-channel GaN HEMTs with f
T
and f
MAX
of 170 GHz and 347 GHz, respectively. Graded-channel GaN HEMTs with a gate periphery of 0.15 mm show a peak power-added-efficiency of 50% at 94 GHz at 2.2 W/mm associated power density after deembedding of the matching network loss of 0.3 dB. Pre-matched power cells with 0.6 mm total gate periphery yielded 2.1 W output power and 3.5 W/mm power density at 94 GHz. Finally, we report three-stage W-band amplifiers with a peak gain of 22.5 dB at 92.5 GHz, yielding 7.5 dB gain per stage.