Split Ring Resonators (SRRs) Based on Micro-Electro-Mechanical Deflectable Cantilever-Type Rings: Application to Tunable Stopband Filters

A new principle for the implementation of tunable split ring resonators (SRRs) is presented. The rings forming the SRRs are partly fixed to the substrate (anchor) and partly suspended (up-curved cantilever). Through electrostatic actuation, the suspended parts are deflected down, the distributed capacitance between the pair of coupled rings is modified, and hence the resonance frequency of the SRR can be electrically tuned. To obtain electrically movable rings, a cantilever-type micro-electro-mechanical-system (MEMS) design and fabrication process is applied. The resonance frequencies at the different switching states are measured by coupling the tunable SRR to a host microstrip line, and reveal that significant tuning ranges can be achieved. This novel tuning concept is applied to the implementation of tunable stopband filters at K_u band as proof-of-concept demonstrators.