A New Low-Pass Filter in Asymmetrical Finline Topology Using Split-Ring Resonators

A variation of the quasi-static equivalent circuit model formulation of miniaturized magnetic resonant structures -i.e., split-ring resonator (SRR)- is presented. The validity of this model is verified by means of an analytical model that uses a new, simple and accurate analytical design formula for the SRRs inductance, full-wave simulations and measurements. These structures are inserted on the opposite side of a compact low-pass filter (LPF) in asymmetrical finline consisting of several notches alternating with a number of single-ridge finline sections. A soft transition from metal waveguide to finline is guaranteed by tapering the finline slot employing a numerically adjusted expression. Finally, experimental results of the filter are presented in order to demonstrate the feasibility of the proposed structure.