Abstract
This paper presents an extremely flat-beam cylindrical lens antenna with a 180 mm ($36~\lambda$ ) diameter lens at 60 GHz. The parameters of lens antennas in the horizontal plane i.e. dielectric constants, radii, and focal length are optimized to widen beams in the vertical plane while obtaining pencil beams in the horizontal plane. The optimization procedure consists of a theoretical method and differential evolution (DE) algorithm. This beam-widening idea is analyzed and proved to be feasible owing to cylindrical apertures, which is quite different from the results of antennas with planar apertures. Then, the permittivity distribution which results in an extremely flat beam is investigated and shows a novel S-shape rather than following either the law of modified Luneberg lens or the Luneberg's Law. Finally, the proposed lens antenna is fabricated and measured. At the design frequency of 60 GHz, the measured 3-dB E- and H-plane beamwidths separately are 100.4° and 2.3°. As compared to the gain peak, the measured and simulated gain drop at ±60° in the E-plane are less than 4 dB and 5 dB, respectively. Measured results show good agreements with the simulated results, thus validating the extremely flat beam of the proposed lens antenna and the effectiveness of the optimization procedure.
Highlights
Wide angle scanning and multiple beams are highly desirable functions required in 5G communication and modern radars
To verify the feasibility of extremely flat beams, we prove that the parameters in the horizontal plane i.e. dielectric constants, radii, and focal length can be used for widening beams in the vertical plane
To analyze the causes of the extremely flat beam, the optimal permittivity distribution is investigated by some comparisons and analysis
Summary
Wide angle scanning and multiple beams are highly desirable functions required in 5G communication and modern radars. Cylindrical lens antennas within parallel plates are attractive solutions due to its symmetrical, focusing properties, and good isolation to external structures [1]–[7]. These lens antennas exhibit a narrow beam and multi-beam capacity in the horizontal plane while showing a wide beam in the vertical plane. Several equivalent media methods are applied to design cylindrical Luneberg lens antennas. An airfilled cylindrical Luneberg lens antenna was presented in [9], [10] by using parallel-plate techniques. By controlling the profile of dielectric, Wu demonstrated fan-beam lens antennas [11], [12].
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