Compact coplanar waveguide bandpass filter based on coupled S-shaped split ring resonators

ABSTRACT This letter is focused on the application of coupled single‐layer S‐shaped split ring resonators (S‐SRRs) to the design of highly compact bandpass filters in coplanar waveguide (CPW) technology. S‐SRRs have been previously demonstrated as miniaturized resonators, particularly suited for applications in conjunction with coplanar line geometries. However, size reduction of CPW filters based on impedance inverters and S‐SRRs is limited by the inverters. Therefore, this letter proposes an alternative geometry of CPW bandpass filters employing S‐SRRs in a configuration based on the theory of coupled resonators. A highly compact third‐order bandpass filter is designed using this principle, and the proposed approach is validated through experiment, demonstrating competitive filter performance achieved in an extremely small area. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:1113–1116, 2015