A Multibeam Tapered Cylindrical Luneburg Lens

We present a cylindrical, multibeam, modified Luneburg lens antenna. The proposed antenna features low-profile, good impedance match, high gain, and wide angle scanning capability. We tapered the thickness of a dielectric disk along its radius to achieve the required refractive index profile of the lens in a nondispersive fashion. Seventeen dielectric-filled waveguide feeds, arranged circumferentially around the focal arc of the lens, provide almost invariant azimuthal scanning in the range of +/- 60 degrees from broadside direction. The lens and the interior of the waveguide feeds are made of the same dielectric material, offering a smooth impedance transition from the feed antenna to the lens. A prototype of the antenna was fabricated and characterized. Measured reflection coefficient is better than -10 dB from 14 to 16 GHz. The isolations between feeds remain higher than 24 dB over the entire operational frequency range. We measured a maximum antenna gain of 20.5 dB with only 1.5 dB gain loss near the maximum 60 degrees scanning angle. The proposed high-gain, multibeam antenna design can be used in a wide range of applications including automotive and surveillance radars.