Reconfigurable bandpass filter based on split ring resonators and vanadium dioxide (VO 2 ) microwave switches

In this paper, we present the design, fabrication and characterization of the first tunable bandpass filter that combines split ring resonators (SRRs) and vanadium dioxide (VO 2 )-based microwave switches. The device consists on a pair of coupled SRRs, feed by means of tapped microstrip lines, that can be connected to metallic patches by electronically activating the VO 2 -based switches. Through the fast and reversible Semiconductor-to- Metal Transition (SMT) of the VO 2 thin films, the electrical characteristics of the SRRs are modified so that their resonance frequency, and as a result the central frequency of the bandpass filter can be electrically tuned. The fabricated filter, designed to operate in the X-band, exhibits a tuning range of nearly 10% where its electrical characteristics (bandwidth, insertion losses, etc.) are roughly preserved.