Duality and Superposition in Split-Ring-Resonator-Loaded Planar Transmission Lines

Three types of coplanar transmission lines loaded with split-ring resonators (SRRs) and including series gaps and/or shunt wires are analyzed in this letter. The phase advance originally predicted for these microstructures can be modified and their frequency selectivity can be enhanced while maintaining the advantage of miniaturization. Full-wave electromagnetic simulations and measurement of different prototypes operating in S- and C-frequency bands are performed for retrieving the effective permittivity and permeability. It is shown that right-handed transmission bands can be obtained slightly below the resonance frequency of the SRRs, giving an effective control of the propagation characteristics in magnitude and phase of these planar transmission lines.