Tunable split rings resonators for reconfigurable metamaterial transmission lines

In this work, it is demonstrated that a microstrip line section loaded with a pair of square shaped split rings resonators (SRRs) and a metallic signal-to-ground via, is a constitutive brick for the fabrication of metamaterial transmission lines with left handed (LH) wave propagation in a narrow band above SRRs resonance. Moreover, it will be shown that the region where the structure is transparent (i.e. exhibits a left handed behavior) can be tuned by merely placing varactor diodes (and the necessary circuitry for biasing) between the inner and outer ring of the SRR. This tunable SRR, called varactor-loaded SRR (VLSRR) by the authors, can open the door to the design of compact reconfigurable resonators and filters based on the metamaterial concept.