Comparison between scrimp horns and stacked Fabry-Perot cavity antennas with small apertures

Scrimp horns and stacked Fabry-Perot (FP) cavity antennas with small radiating apertures (≤ 2.5λ₀) are very attractive antenna solutions for global Earth illumination or primary feeds of focal arrays. Several antennas of each type have been optimized for different radiating sizes, and their radiation characteristics are compared in terms of aperture efficiency and pattern quality. It is shown that scrimp horns provide excellent aperture efficiencies over large bandwidths, but are limited to applications requiring aperture sizes smaller than 2λ₀. It is also demonstrated that the stacked FP cavity antennas are very promising for aperture sizes varying between 1.5λ₀ and 2.5λ₀, and show comparable performances to scrimp horns for aperture size lower than 2λ₀; they also exhibit higher aperture efficiencies for apertures larger than 2λ₀ while keeping the antenna height fixed at λ₀ in contrast to scrimp horns with height increases naturally with the aperture size.