Analysis and Design Guidelines for Wideband CRLH SRR-loaded Coplanar Waveguide

This article presents a novel lumped-element equivalent circuit model for split-ring resonator (SRR)-based composite right/left-handed (CRLH) coplanar waveguide (CPW). The proposed model has closed-form expressions in terms of the parameters of the constituent transmission lines and is valid over a wide frequency range. This article also presents a novel slotline to coupled microstrip (MS) line E-plane T-junction. Based on the circuit model and the proposed junction, systematic design procedures for ultrawideband balanced SRR-based CRLH CPW unit cells that benefit from the geometry of the unit cell and do not rely on adding extra components or parametric iterations are developed. This article also explains the layout constraints and presents alternatives to realize wideband designs. Two CPW unit cells using SRR and edge-coupled (EC) SRRs are designed, fabricated, and characterized. Simulations, which are in good agreement with measurements, show that the operating bandwidth can reach 97% and 78.21% for the two cells, respectively.