Design of Wideband Bandstop Frequency-Selective Structures Using Stacked Parallel Strip Line Arrays

We present a novel design procedure to implement wide bandstop frequency-selective structures using the periodic arrays of vertically stacked parallel strip lines (PSLs). The proposed structures employing the PSLs can simplify their design through equivalent circuit models. Three structures are designed based on the simple equations to demonstrate the proposed procedure. The first structure features an independent design of the air and substrate regions, allowing the use of higher order resonances to extend the bandwidth. The second structure employs a cascaded array, and the third represents a hybrid of both the first and second structures. Design examples have been provided for each proposed structure, achieving -10 dB fractional bandwidths of 78%, 100%, and 137% for the first, second, and third structures, respectively. The operating principles and the design procedures are explained along with the experimental verification for the first two structures.