| Summary: | Two types of cost-efficient antennas based on dielectric gradient index dielectric lens have been designed for 5G applications at <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>28</mn><mo> </mo><mi mathvariant="normal">G</mi><mi mathvariant="normal">H</mi><mi mathvariant="normal">z</mi></mrow></semantics></math></inline-formula>. The first is a linearly polarized flat lens antenna (LP-FLA) for terrestrial 5G communications. The second is a novel circularly polarized stepped lens antenna (CP-SLA) for 5G satellite services. An efficient design method is presented to optimize and conform the lens topology to the radiation pattern coming from the antenna feeder. The LP-FLA is fed by a traditional linearly polarized pyramidal horn antenna (PHA). The CP-SLA is fed by an open-ended bow-tie waveguide cavity (BCA) antenna. This cavity feeder (BCA), using cross-sections with bow-tie shapes, allows having circular polarization at the desired frequency bandwidth. The two types of presented antennas have been manufactured in order to verify their performance by an easy, low-cost, three-dimensional (3D) printing technique based on stereolithography. The peak realized gain value for the flat (LP-FLA) and stepped (CP-SLA) lens antennas have been increased at <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>28</mn><mo> </mo><mi mathvariant="normal">G</mi><mi mathvariant="normal">H</mi><mi mathvariant="normal">z</mi></mrow></semantics></math></inline-formula> to <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>25.2</mn></mrow></semantics></math></inline-formula> and <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>24.8</mn><mo> </mo><mi mathvariant="normal">d</mi><mi mathvariant="normal">B</mi><mi mathvariant="normal">i</mi></mrow></semantics></math></inline-formula>, respectively, by disposing the lens structures at the appropriated distance from the feeders. Likewise, using an array of horns (PHA) or open-ended bow-tie waveguide cavity (BCA) antenna feeders, it is possible to obtain a maximum steering angle range of 20° and 35°, for a directivity over <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>15</mn><mo> </mo><mi mathvariant="normal">d</mi><mi mathvariant="normal">B</mi><mi mathvariant="normal">i</mi></mrow></semantics></math></inline-formula> and <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>10</mn><mo> </mo><mi mathvariant="normal">d</mi><mi mathvariant="normal">B</mi><mi mathvariant="normal">i</mi></mrow></semantics></math></inline-formula>, in the planar and stepped lens antennas, respectively.
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