Efficiency enhancement of single off-axis and multiple overlapping beam reflectors using dielectric-covered focal plane array feeds

Reflector antennas fed by dense focal plane arrays (FPAs) are known for their high aperture efficiency, low scan loss, and ability to achieve closely overlapping beams and thus improved continuity in the field of scan. These benefits are possible because FPAs comprise electrically small elements with diameters within half a wavelength, which sample the focal plane fields to a high resolution. This work explores the prospects of further enhancing the total efficiency of FPA-fed reflector systems by using dielectric covers placed over FPA feeds composed of open-ended waveguides. The parameters investigated are the permittivity and thickness of the dielectric layer. We will demonstrate the ability of these covers to improve the overall efficiency of reflectors compared to that of reflectors fed by uncovered FPAs, over several beam widths of scan for single steered beams, as well as to enhance the individual constituent beam efficiencies of simultaneously overlapping multiple beams.