An explicit design technique for wideband couplers and high quality filters using periodic topology

A novel approach is introduced for computer-aided design (CAD) of wideband couplers and high-quality filters using periodic structures. This design technique consists of two explicit steps. The first step is to obtain single periodic cell parameters for a given electrical specification or vice versa by the use of field-theoretical approaches in conjunction with Floquet´s theorem. The next step is to determine the number of the given periodic cells used in wideband couplers or high-quality filters for a desirable coupling or filtering characteristic. Experimental prototypes and theoretical simulations validate the present design approach with satisfactory accuracy for both a 10-dB coupler and a stopband filter based on nonuniform periodic planar topology. Some interesting features of lossy and lossless periodic structures with a finite number of cells are discussed.<>