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

© 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:1113-1116, 2015 © 2015 Wiley Periodicals, Inc. 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.