Synthesis of open complementary split ring resonators (OCSRRs) through aggressive space mapping (ASM) and application to bandpass filters

This paper deals with the automated synthesis of open complementary split ring resonators (OCSRRs) using aggressive space mapping (ASM) for the first time. These open resonators are electrically small planar elements useful for the implementation of shunt LC resonators in microstrip or coplanar waveguide technology. However, their synthesis is in general complex and requires the experience of the microwave engineers. To solve this limitation, and to ease any design process involving OCSRRs, we have developed an efficient iterative synthesis tool based on ASM, able to provide the physical dimensions of the resonator from the required reactive elements (given by specifications) and substrate parameters. As an example of application, the tool is used for the synthesis and design of a planar wideband bandpass filter based on OCSRRs coupled through admittance inverters. Due to the inherent transmission zeros associated to the OCSRRs, these filters exhibit good stop band performance, with high selectivity at the upper transition band.