A geodesic slotted cylindrical (GSC) antenna having a shaped elevation pattern and a narrow or shaped azimuth beam that can be scanned 360. degree. in the azimuth plane. The azimuth radiation pattern of the GSC antenna can be reconfigured through the use of interchangeable beam forming feed networks. The GSC antenna comprises a parallel plate waveguide formed by spaced-apart inner and outer cylinders constructed from conductive material. Radiation occurs from a stack of circumferential slots in the outer cylinder. By varying the slot spacing with the azimuth angle, the elevation pattern can be altered as a function of the azimuth angle. The GSC antenna can be excited by a number of equally spaced probes on a circle at the base of the cylinders. The feed radius is typically smaller than the outer cylinder's radius to minimize the number of active components and to minimize the number of spurious ray paths that can wrap around inside the cylinder's parallel plate region. The probes can be phased so that rays from each probe will travel between the parallel cylindrical plates and radiate from the slots to produce a beam that is focused in azimuth. The elevation pattern can be scanned or altered by mechanically moving a tapered dielectric insert within the parallel plate region.
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