Design of Wideband, FSS-Based MultiBeam Antennas Using the Effective Medium Approach

We present the design, simulation, and measurement results of a broadband, low-profile, multibeam antenna. The antenna uses multiple feed elements placed on the focal plane of a planar microwave lens to achieve high-gain, multibeam operation with a wide field of view. The lens is based on a recently reported design employing the constituting unit cells of appropriately designed miniaturized-element frequency selective surfaces (MEFSSs) as its spatial time-delay units. A new technique for modeling such lenses is also presented that greatly simplifies the full-wave electromagnetic simulation of MEFSS-based lenses. This technique is based on treating the pixels of the lens as effective media with the same effective permittivity and permeability and significantly reduces the difficulty of modeling and optimizing the proposed multibeam antenna with its relatively large aperture size in a full-wave electromagnetic simulation tool. Using this procedure, a prototype multibeam antenna operating in the 8-10 GHz range is designed. The prototype is fabricated and characterized using a multiprobe, spherical near field system. The measurement results are in good agreement with the simulation results obtained using the proposed simplified modeling technique. Measurements demonstrate consistent radiation characteristics over the antenna's entire operational band with multiple beams in a field of view of +/- 45 degrees.