Filter Parameter Extraction for Triple-Band Composite Split-Ring Resonators and Filters

A configuration of composite resonators consisting of three split-ring resonators is proposed to obtain a triple-band response with two transmission zeros between the passbands. Two new topologies are presented to design triple-band filters with controllable responses. A systematic filter design approach is presented based on a filter coupling model. The model is established to enable triple-band filter design with controlled passbands. Two methods are proposed and compared for the extraction of filter parameters. Coupling between nonadjacent elements is considered in the model and shown to have a significant effect. By changing the orientation of the coupled composite resonators, it is possible to introduce additional transmission zeros. Two sixth-order filter examples illustrate the use of the coupling model with the filter design approach to design filters with specified responses. The limitations of this filter topology are discussed.