Electrostatical coupling-spring for micro-mechanical filtering applications

This paper presents a novel method of implementing coupled resonator micro-mechanical (MEMS) filters without mechanical springs. The method proposes to use an electrostatical spring, formed by two or more electrostatical transducers, to couple single resonators. This spring has a stiffness controlled by bias voltages, thus variable-bandwidth filters can be obtained. An original biasing scheme is used to avoid external connections on sensitive signal nodes. Theoretical analysis as well as experimental results on 4-th order bandpass filters at 2.5 MHz are presented.