Truncated 2-D Gutman Lens Antenna With Planar Feeding Surface for Stable Wide-Angle Beam Scanning in Millimeter-Waveband

摘要

A truncated 2-D Gutman lens (GL) antenna (GLA) with planar feeding surface is investigated for millimeter-wave (MMW) applications. To flatten the feeding surface of Luneburg lens (LL) while maintaining the wide-angle scanning capability, three effective measures have been taken. First, the focal points of LL are shifted to the interior to obtain GL (f = aR, 0 <a < 1) by utilizing Hamiltonian optics, and then the GL is truncated through the interior focal circle at t = bR (b < a) to provide a focal surface with a larger radius of curvature. Second, the feeds are arranged on two sides of the focal surface to reduce the distance variation between the feeds and focal surface, thus reducing the gain fluctuation in the wide-scanning range. Third, two metal posts are introduced near the edge feeds to perturb the electric field in the vicinity, further enhancing the gain of edge beams. Consequently, a truncated GL with stable wide-angle beam-scanning performance is achieved, and simultaneously its permittivity features a narrow range and a regular distribution profile which is easy to implement. Moreover, to facilitate the process of the GL, its desired permittivity is synthesized using dielectric-post cells of different sizes and complementary air-hole cells of the same material. For validation, a truncated 2-D GL with a thickness of 4.5 mm and a diameter of 65 mm is processed using 3-D printing technology, and tested with nine feeding patch antenna elements that are linearly arranged on a planar surface. The measured results indicate that the obtained GLA can achieve a wide-angle beam-scanning range of +/- 63(degrees) at 30 GHz, with a gain fluctuation of 0.7 dB and a cross-polarization level of less than -20 dB.

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