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Dispersion Characteristics of a Cylindrical Electromagnetic Band Gap Structure

In this letter, a new analytical expression for the dispersion equation of radially periodic structures is derived. The periodic structure is considered as a set of parallel cylindrical frequency selective surfaces, and the dispersion equation is calculated by using a transmission line model. Using this result, the dispersion proprieties of cylindrical electromagnetic bandgap structures composed of continuous or discontinuous metallic wires are presented. It is shown that the band structures of these materials can be determined by using the proposed dispersion equation. Cylindrical periodic materials have potential applications for designing directive antennas, circular high impedance surfaces, or agile antennas