Analysis of space harmonic selectivity of period-varying folded waveguide

A period-varying folded waveguide is formed by varying the period ofa folded waveguide. It has the advantages of the space harmonicselectivity and the wide bandwidth. However, the regularities of thevariety of these period-varying folded waveguides are unavailablefrom the published papers. In order to solve this problem, theprinciple of the space harmonic selectivity of a period-varyingfolded waveguide is analysed, and the conditions to select the spaceharmonic for this slow wave system are obtained. In addition, thespace harmonic selectivities for a linear period-varying foldedwaveguide and a hyperbolic sine-varying period folded waveguide arealso analysed as examples.