Split rings for metamaterial and microwave circuit design: A review of recent developments (Invited paper)

This article is a review of recent applications of split rings to the design of planar microwave circuits based on metamaterial concepts. The considered resonators, namely, split-ring resonators (SRRs), complementary SRRs (CSRRs), and their open counterparts (OSRRs and OCSRRs), are reviewed, and the equivalent circuit models of artificial lines based on such resonators, including parasitics, are presented and discussed. The second part of the article is devoted to highlight some recent applications of the considered resonators. This will include the design of dual-band components and wideband bandpass filters based on the combination of OSRRs and OCSRRs, the design of tunable components based on cantilever-type SRRs, and the design of CSRR-based differential (balanced) lines with common-mode suppression. (c) 2012 Wiley Periodicals, Inc. Int J RF and Microwave CAE 22:439458, 2012.