Miniaturized Bandstop Filters Using Slotted-Complementary Resonators

This paper presents a technique to miniaturize bandstop filters applicable for radiofrequency/microwave applications. The technique comprises the use of small resonant inclusions bridged with a slot, etched from the metallic ground plane underneath the filter’s microstrip line segment. Unlike artificial magnetic materials, for instance split-ring resonators (SRRs) that respond to vertical magnetic field, complementary SRRs (CSRRs) resonate upon an excitation of an axial time-varying electric field. Numerical full-wave studies are presented here to validate and proof the proposed concepts. It is found that high miniaturization factors can be achieved for the filters loaded with the proposed slotted complementary resonators in comparison to nonslotted resonators. Furthermore, sensitivity analysis is conducted to study the effect of geometrical parameters of the proposed slotted resonators as well as the effect of the choice of host media on the suppression bandwidth and rejection level of such filters. Miniaturized bandstop filters based on developed slotted-complementary spiral resonators are also proposed and numerically evaluated.