A Non-Uniform Distributed GaN LO Amplifier for Wideband 5–38 GHz Applications

A wideband LO amplifier is designed using a single-stage non-uniform distributed topology that contains 10 cells with varied 0.18 $\boldsymbol{\mu}\mathbf{m}$ GaN HEMT peripheries interconnected by tapered gate and drain lines to provide improved large signal terminations to the transistors. Non-uniform capacitive division is incorporated at all cell gates for increased bandwidth, while gate resistors are tailored to ensure stability and produce a bias path. Simulated performance and probed measurements show that for the first time a GaN MMIC PA with more than 35 dBm maximum output power, $< \boldsymbol{2}$ dB of gain ripple, and $> \boldsymbol{15\%}$ PAE has been demonstrated for a 5–38 GHz bandwidth at the die level. For packaged measurements at $\boldsymbol{P}_{in}=\boldsymbol{28}$ dBm, the 2.3 mm x 3.0 mm amplifier measured (including package losses) an average of 32.5 dBm output power and 5 dB gain with $> \boldsymbol{10\%}$ PAE from 5–35 GHz, where the upper end of the band was limited by the external fixture.