A Compact DC-110GHz SPST Switch in 22nm FDSOI CMOS

This brief reports a compact DC-110GHz single-pole single-throw (SPST) switch in 22nm FDSOI CMOS technology. The switch adopts solely three n-MOSFETs, two of them with a special device option to reduce the substrate parasitic effects, and a third n-MOSFET in parallel to the gate resistance of the series n-MOSFET to improve isolation. Unlike prior wideband mm-wave switches, it does not make use of any large passive components, such as spiral inductors, transformers and transmission lines, which are prone to large parasitic effects, including losses, and require large area on silicon. Altogether, the novel switch circuit allows a very compact design, low losses and high isolation performance. The switch exhibits an insertion loss lower than 3.1 dB, an isolation better than 22 dB, and a return loss better than 12 dB, over the entire frequency range from DC to 110 GHz. The area on die amounts to
$160~\mu \text{m}^{2}$
, that is up two or more orders of magnitude smaller than prior wideband mm-wave SPST switches.