Design of lens-based, broadband multi-beam antenna apertures using effective medium theory approach

We present a new technique for designing a broadband, low-profile, multi-beam high-gain antenna. In order to achieve high-gain multi-beam operation with a wide field of view, the antenna uses multiple feed elements placed on the focal plane of a planar microwave lens. The constituting elements of the lens are unit cells of appropriately-designed miniaturized-element frequency selective surfaces (MEFSSs) which act as spatial-time-delay-units. An effective medium approach for designing such lenses is also presented that greatly simplifies the full-wave electromagnetic simulation of MEFSS-based lenses. In this approach, the pixels of the lens are treated as homogenous effective media which reduces the difficulty of the modeling and optimizing of the proposed structure with relatively large aperture size in a full-wave electromagnetic simulation tool. Using this technique, a prototype multi-beam antenna operating in the 8-10 GHz range with an overall thickness of 2λ₀, inclusive the separation between the feed antenna and the lens is designed. Measurements demonstrate consistent radiation characteristics over the antennas entire operational band with multiple beams in a field of view of ±45°.