Parameter Analysis of Millimeter-Wave Waveguide Switch Based on a MEMS-Reconfigurable Surface

Abstract

This paper presents a novel concept of a millimeter-wave waveguide switch based on a microelectromechanical (MEMS)-reconfigurable surface with insertion loss and isolation very similar to high performance but bulky rotary waveguide switches, despite its thickness of only 30 μm. A set of up to 1470 micromachined cantilevers arranged in vertical columns are actuated laterally by on-chip integrated MEMS comb-drive actuators, to switch between the transmissive state and the blocking state. In the blocking state, the surface is reconfigured so that the wave propagation is blocked by the cantilever columns short-circuiting the electrical field lines of the TE 10 mode. A design study has been carried out identifying the performance impact of different design parameters. The RF measurements (60-70 GHz) of fabricated, fully functional prototype chips show that the devices have an isolation between 30 and 40 dB in the off state and an insertion loss between 0.4 and 1.1 dB in the on state, of which the waveguide-assembly setup alone contributes 0.3 dB. A device-level yield analysis was carried out, both by simulations and by creating artificial defects in the fabricated devices, revealing that a cantilever yield of 95% is sufficient for close-to-best performance. The actuation voltage of the active-opening/active-closing actuators is 40-44 V, depending on design, with high reproducibility of better than (σ = 0.0605 V). Lifetime measurements of the all-metal, monocrystalline-silicon core devices were carried out for 14 h, after which 4.3 million cycles were achieved without any indication of degradation. Furthermore, a MEMS-switchable waveguide iris based on the reconfigurable surface is presented.