Applications of vanadium dioxide (VO2)-loaded electrically small resonators in the design of tunable filters

This paper presents some examples of the large possibilities offered by the combination of vanadium dioxide (VO₂)-based switches and split ring resonators (SRRs) for the design of compact filters with frequency agility. First, the synthesis of an all-integrated reconfigurable four pole band-stop filter is presented. It follows the design of a digitally tuned band-reject filter. Preliminary results of the fabricated devices operating in the X-band under thermal actuation are presented. The tuning principles of both structures are validated. Good agreement between experimental data and electromagnetic simulations is obtained. This paper opens the way to the design of compact tunable microwave filters based on new principles that rely on the combination of VO₂ and SRRs, but the ideas presented in this work can also be extended to many other electrically small resonators.