  This paper reports the experimental characterization at the cryogenic
temperature of a compact mm-wave broadband single-pole single-throw (SPST)
switch in 22nm FDSOI CMOS technology. The switch consists of two n-MOSFETs with
a special device option to reduce the substrate parasitic effects, and a third
n-MOSFET to improve isolation. Unlike prior wideband mm-wave switches, it does
not require any large passive components, allowing a very compact design, low
loss and high isolation performance. The cryogenic measurements at 2 K show an
insertion loss lower than 2.3 dB, an isolation better than 25.3 dB, and the
return loss better than -11.5 dB, over the entire frequency range from DC to 70
GHz.
