A 250–310 GHz Piezo-Motor Actuated SPDT Waveguide Switch With High Isolation

The design and performance of a subterahertz (sub-THz) single-pole double-throw waveguide switch is presented, operating from 250 to 310GHz. The piezo-motor actuated switch is suitable for high-fidelity calibration of THz spectroscopy and radiometry instruments, thanks to its low insertion loss,
$< -0.6 \,\mathrm{dB}$
, low return loss,
$< -20 \,\mathrm{dB}$
, and high isolation,
$< -75 \,\mathrm{dB}$
. The high isolation and low leakage is achieved by using an array of rectangular metal pillars surrounding the waveguide apertures, which act as an electromagnetic band gap structure in the proximity of the switching element. The switching element is controlled with micrometric precision to direct the signal through a U-bend waveguide to either one of the two output waveguide apertures. The reliability and durability of the switch is tested by performing one million switch actions at its maximum switching rate of 1 Hz, resulting in a mean positioning error better than 2
$\mu \text{m}$
.