Step Impedance Resonator (SIR) Loaded with Complementary Split Ring Resonator (CSRR): Modeling, Analysis and Applications

A novel resonant element that combines a step impedance resonator (SIR) and a complementary split ring resonator (CSRR) is presented. The specific topology consists of a shunt connected SIR in microstrip technology, with a CSRR etched in the ground plane, beneath the SIR capacitive patch. A lumped element circuit model of this composite resonator is proposed and validated by parameter extraction and comparison of the circuit response to full-wave electromagnetic simulations. Such model consists of a series LC resonator connected in series with a grounded parallel LC resonator. The CSRR-loaded SIR resonator exhibits a pole and two transmission zeros. This composite resonator is useful for the implementation of highly selective bandpass filters in microstrip technology. Moreover, since the CSRR can be used as sensing element, sensitive to the properties of its surrounding medium, the structure can be also applied to the implementation of sensors for dielectric characterization.