A zipper RF MEMS tunable capacitor with interdigitated RF and actuation electrodes

Abstract

This paper presents a new RF MEMS tunable capacitor based on the zipper principle and with interdigitated RF and actuation electrodes. The electrode configuration prevents dielectric charging under high actuation voltages. It also increases the capacitance ratio and the tunable analog range. The effect of the residual stress on the capacitance tunability is also investigated. Two devices with different interdigital RF and actuation electrodes are fabricated on an alumina substrate and result in a capacitance ratio around 3.0 (Cmin = 70–90 fF, Cmax = 240–270 fF) and with a Q > 100 at 3 GHz. This design can be used in wideband tunable filters and matching networks.