High standoff dual-mode-actuation MEMS switches

MEMS switches based on a dual-mode actuation scheme that simultaneously allows for large standoff heights and low clamping voltages have been designed and fabricated. These devices are based on the use of a transient external magnetic field to bring the actuating portion of the switch close to a dielectric-coated clamping electrode, followed by application of an electrostatic clamping voltage to keep the switch closed. Since the clamping voltage is applied when the switch is closed, this voltage can be relatively small. This approach is particularly attractive for RF applications such as arrays of switches in reconfigurable aperture antennas. The arrays of switches are simultaneously closed by the magnetic field generated by an external magnetic source, then selected switches are clamped by electrostatic force using low voltages to maintain the ON state. Their utility in such an array has been demonstrated and several different design variations have been explored to improve switch performance. Contact resistance as low as 0.37 Ω has been achieved, with actuating field strength of 40 Gauss. These switches possess a large open state air gap (25 μm), and are able to pass high currents in excess of 1 A under low frequency or DC operation. The large OFF state impedance allows for their usage in switching applications in RF devices. Their high frequency functionality has been tested to find that their open-state impedance was identical to that of a perfect open up to 9 GHz and their RF reconfigurability has been demonstrated in a monopole/dipole test bed.