A 2-D Multibeam Half Maxwell Fish-Eye Lens Antenna Using High Impedance Surfaces

This letter describes the design and measurement of a planar multibeam half Maxwell fish-eye (HMFE) lens antenna with seven beams in azimuth based on variable high impedance surfaces (HISs). The desired refractive index profile is controlled by using slotted square mushroom metallic cells of different sizes on a grounded dielectric slab. The lens antenna, 6.2 lambda x 3.1 lambda in lens plane and 0.65 lambda total height, is fabricated and characterized in TM mode at 13 GHz for both single-and multiple-beam configurations. The optimized lens for single-beam operation achieves 14.1 dBi measured gain, 67 degrees and 12 degrees half-power beamwidth for E-plane and H-plane, respectively, and 55.3% impedance bandwidth for -10-dB return loss. This lens can be used to launch multiple beams by implementing an arc array of seven-element short monopoles at the periphery of the lens. The measured overall scan coverage is up to 45 degrees with gain dropless than 2.4 dB. Its low profile, light weight (only 136 g), and ease of manufacturing makes it well suited for Local Multipoint Communication Systems (LMCS).