Chebishev Bandpass Spatial Filter Composed of Strip Gratings

A new filter composed of a cascade of strip gratings with a 3rd order Chebishev frequency response that operates within a prescribed frequency band, is presented in this paper. Theoretical development was undertaken to establish equivalence between electromagnetic characteristics of a frequency selective surface (FSS) configuration and equivalent model based on circuit parameters that are used in the realization of Chebishev frequency response. The FSSs replace the impedance inverter elements in circuit implementation of the filter and the spacing between FSSs, which are adjusted to obtain the desired electrical performance, correspond to resonant elements in the circuit implementation. Dielectric slabs similar to the ones that were employed in FSS stages were used as the spacers between the constituent FSS layers to increase the robustness and rigidity of the structure. The fabrication process is described in detail and methods are introduced to account for tolerances in the permittivity and etching process during the design stage. Close agreement between measurement results demonstrates the validity of the design procedure.