Multi-beam, multi-lens microwave antenna providing hemispheric coverage

Abstract

The novel multi-beam multi-lens antenna of the present invention provides multi-beam coverage over a hemisphere or greater three-dimensional spatial coverage region. In its simplest configuration, the antenna comprises two microwave lenses whose design is integrated to minimize path length errors and aberrations for beams over a 360.degree. azimuth coverage range. The antenna comprises a 3-D focal ring bootlace first microwave lens that is a figure of revolution and a non-planar dome second microwave lens which provides the refractive properties necessary to obtain the hemispheric coverage while providing additional degrees of freedom necessary to reduce errors and aberrations of the lens system to within acceptable levels. Both lenses are time delay lenses to effect broadband operation and are circularly symmetric. This symmetry results in antenna performance that is invariant with azimuth beam position. The parameters that are available for design optimization include the bootlace lens inner and outer surface contours, the interconnecting delay lines, the relative radial positioning of the lens elements on the inner and outer surface, the dome lens surface contours and the dome delay lines in the constrained embodiment or gradient function in the dielectric embodiment. These parameters are determined to provide a minimum rms path length error across the radiating aperture in the desired beam directions.