A dielectric-coated circumferential slot array for omnidirectional coverage at microwave frequencies

The design and development of a resonant array of circumferential shunt slots cut into the broad wall of a ring waveguide are presented. This antenna, which is recessed into a metal cylinder and dielectric coated, provides nearly omnidirectional coverage. Calculations using an idealized model consisting of a dielectric-coated flush-mounted array on a metal cylinder were performed and used as the primary basis for design. The array recess design was experimentally determined and shown to control the elevation pattern when the recessed array is mounted on a variety of spacecraft shapes. The tolerance problems and the related trapped wave effects encountered in the development of the array are discussed.