Narrow-band filtering by means of triangular meta-material resonators based on RF MEMS cantilevers in CPW configuration

Abstract

Triangular resonators, designed by using Radio Frequency Micro Electro Mechanical Systems (RF MEMS) cantilevers in coplanar waveguide (CPW) configuration, have been proposed, fabricated on alumina and on silicon substrates and tested up to 40 GHz. They can be utilized as building blocks for realizing reconfigurable filters. A triangular split ring resonator has been etched in the central conductor of the CPW transmission line and the split is provided by the presence of a technologically actuated cantilever beam, i.e. with metal directly deposited without the sacrificial layer, to emulate the ideal actuation and to get preliminary information of the expected microwave response in comparison to numerical simulations. Two main configurations of the triangular transmission line have been studied for narrow-band microwave switching, the first one without the MEMS cantilever and the second one with a technologically actuated MEMS cantilever switch. Because of the contributions of both the resonator and the switch, the device has a narrow band filtering feature. Moreover, these geometries can also be characterized in the broad class of metamaterial devices, because the unit cell can be described by negative equivalent electric permittivity and/or magnetic permeability, by means of a transmission line parameters extraction method. This finding contributes to the possibility of miniaturization implementations of the resonating structures. A simple but effective lumped element circuit for the modeling of the single triangular resonator is presented in the end.