220–325 GHz high-isolation SPDT switch in InP DHBT technology

A broadband single-pole-double-throw (SPDT) switch is presented covering 220–325 GHz in 800 nm transferred substrate InP DHBT technology. The SPDT switch configuration employs shunt-topology. The circuit achieves an isolation of >36 dB within the band with very low DC power of 9 mW, benefitting from the low intrinsic capacitance of the transistors. This is the highest reported isolation for wideband SPDT switches covering 220–325 GHz. This three-stage SPDT switch also demonstrates the highest isolation of 12 dB per stage in this frequency range.