Wide flare-angle horn antenna with enhanced directivity using a third-order bandpass frequency selective surface

This paper describes the performance of a wide flare-angle horn antenna loaded with a low profile frequency selective surface (FSS) designed to enhance the horn directivity. The FSS structure is made of three metallic layers separated by two thin dielectric substrates. The metallic layers are composed of two-dimensional periodic elements with sub-wavelength dimensions and periodicity. This FSS behaves as a third-order spatial bandpass filter and is used here as a phase correcting device in the horn mouth. The corresponding discrete lens is designed for a short pyramidal horn with an aperture of 2.7λ₀×2.7λ₀ and a flare angle of 97.5°. The horn height is only 1.24λ₀. The numerical results demonstrate that the antenna aperture efficiency reaches 65% over a 16% bandwidth around 4 GHz.