Microwave Transmission Through an Array of Ring Slots in a Metal Sheet Capped With Concentric Metal Rings

The resonant transmission response of an array of ring slots in a metal sheet, capped with concentric copper rings (annuli) is explored both experimentally and numerically. This frequency selective surface (FSS) shows dual pass band behavior due to two resonances associated with two annular resonant spaces (annular cavities). One is formed between the outer edge of the annulus and the metal beyond the outer circumference of the ring slot, and the other is formed between the inner edge of the annulus, and the inner circumference of the ring slot. The experimental results are in agreement with finite element method (FEM) modeling predictions. Using the same modeling, the behavior of multi pass band structures using a series of concentric copper annuli over a similar series of concentric annular slots in a ground plane is also explored.