Systematical analysis for the mixed couplings of two adjacent modified split ring resonators and the application to compact microstrip bandpass filters

In this paper we synthesize a new kind of modified split ring resonator (SRR) and characterize its mixed couplings between two adjacent such SRRs with all the possible arrangements on one side of a conventional dielectric substrate. Based on the analysis of the mixed couplings, the compact microstrip bandpass filters composed of the proposed modified SRRs are systematically analyzed. We found that two designs out of all the cases have quite well bandpass filter characteristics, e.g., low insert loss within the wide passband, sharp reductions and transmission zeros out of the passband, and harmonic suppression characteristics for a wide frequency range. Both experimental demonstrations and numerical simulations are performed to verify the designed filters and the results agree well with each other. Such kind of filter design can be flexibly integrated in the miniaturized radio frequency/microwave circuits