Mm-wave single-pole single-throw m-HEMT switch with low loss and high linearity

This Letter presents a single-pole single-throw (SPST) switch for high-power applications in the mm-wave frequency band. A stacked-FET structure is adopted in the shunt switching cell for reducing the insertion loss and improving the linearity of the switch. To enhance the isolation, the parasitic inductance of the stacked-FET structure is resonated out by connecting a series capacitor. The number of stacked FETs in each shunt cell and the number of the shunt cells are optimised considering the trade-off among the insertion loss, isolation, and linearity. The SPST switch is fabricated in a 70-nm GaAs m-HEMT process. The measurement shows that the insertion loss is <1.1 dB, and the isolation is >25 dB over the frequency from 59 to 77 GHz. Both the insertion loss and isolation are not compressed at all until the input power reaches 19.5 dBm at 75 GHz.