Ultra-Thin Planar Reflection-Less Lens Based on Miniaturized-Element Frequency Selective Surfaces for a 230 GHz Polarimetric Single-Aperture Radar

A 230 GHz low-mass, ultra-thin, planar, and reflection-less lens antenna based on miniaturized element frequency selective surfaces (MEFSS) is designed, fabricated, and tested. This lens is designed to provide a narrow beam (0.88°) and high gain (44 dBi) while having a very low reflection coefficient (−35 dB at resonance) measured at its feed. This antenna is a key component in a dual-polarized, and single-aperture radar designed for radar studies of traffic scenes in the 230 GHz band. The phase compensation for the lens is accomplished locally with phase delays through distributed 3-pole spatial filters that make use of only shunt elements. This lens includes three MEFSS-gold patterned layers and two layers of glass substrate. The lens has
$\mathrm{F}/\mathrm{D}=1.4$
and is fed by a dual-polarized horn whose half-power beamwidth covers the aperture of the lens. The fabricated 4″ lens is only 387um thick and weighs 7g which is 13 times lighter and 44 times thinner than an equivalent dielectric lens (the same size and F/D) without degradation in gain but much improvement in average reflection coefficient from 226–234 GHz(> 10dB).