A High-Performance 220–290 GHz Micromachined Waveguide Switch Based on Interference Between MEMS Reconfigurable Surfaces

This article presents a highly integrated novel silicon micromachined single-pole-single-throw waveguide switch based on two microelectromechanically reconfigurable switching surfaces (MEMS-RSs), which allows optimizing the switching performance by tuning the interference between the two such MEMS-RSs utilizing integrated electrostatic comb-drive actuators. The switch prototype is implemented with axially aligned standard WR-3.4 waveguide ports with a total footprint of 3 mm×3.5 mm×1.2 mm. The measured blocking (
off
) state insertion loss (isolation) and return loss, measured between two standard WR-3.4 waveguide flanges, are 28.5–32.5 dB and better than 0.7 dB, and the propagating (
on
) state insertion and return losses are 0.7–1.2 dB and better than 17 dB in the 220–290 GHz frequency band, respectively. The measured results were in excellent agreement with the simulation data, implying 27.5% fractional bandwidth, which is very close to a full waveguide band performance. For further investigations, two variants of the switching circuit with only a single MEMS-RS and without any MEMS-RSs have also been fabricated. The single MEMS-RS switch achieved the
off
-state isolation,
on
-state insertion loss, and return loss of only 11.5–12.5 dB, 0.8–1.3 dB, and better than 12 dB from 220 to 274 GHz, respectively, which clearly indicates the drastic performance improvement of the interference-based double MEMS-RS switch design. Moreover, measurement of the waveguide-only reference structure showed that the waveguide section alone attributed to 0.2–0.5 dB of the measured
on
-state insertion loss of the double MEMS-RS switch, and the rest is due to the introduction of the MEMS-RSs inside the waveguides.