46–102 GHz GaN Balanced Cascode Amplifier-Isolator

This paper details a solid-state transistor isolator using a balanced cascode amplifier topology. The circuit design, with a focus on stability, is discussed. The amplifier is implemented in a 40nm GaN-on-SiC process with an overall size of 2.1mm by 1.6 mm. Measured small-signal S-Parameters are in good agreement with simulation with a flat
$S_{21}$
of 7 dB over a 3-dB bandwidth of 46 GHz to 102 GHz. Reverse isolation is above 32 dB over this frequency range. Large-signal measurements from 82 GHz to 96 GHz show a 1 dB input compression point between 5–6 dBm with corresponding output power up to 13.7 dBm. The presented circuit is well suited for use in wideband millimeter-wave MMIC front ends, as e.g. an isolated driver.