A finite length cylindrical FSS is proposed as a spatial filter for both transmitting and receiving antennas. This filter has the advantage of not perturbing the omnidirectional property of the enclosed antenna. The proposed surface is constructed up as cylindrical array of rectangular conducting patches. The strips are arranged periodically in the φ- and z-directions. The electric field integral equation (EFIE) approach is used for analyzing the characteristics of the proposed spatial filter. The Rao-Wilton-Glisson (RWG) basis functions are used for current expansion on the conducting strips. The mutual effects between the filter and the antenna can be accurately investigated. The effects of some dimensional parameters on the filter characteristics, such as, the axial and angular spacing between the array elements, the length and the radius of the cylindrical surface are studied over a wide frequency range. The oblique incidence of plane waves on such a cylindrical filter is studied with varying the direction of incidence. The performance of the proposed spatial filter is examined when operating with nearby antennas. The effects of such a filter on the input impedance, VSWR, and radiation pattern of an enclosed bowtie antenna are investigated over a wide frequency range.
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