Abstract
The authors introduce two flat graded-index (GRIN) lens designs in this study. First of these is a thick lens, which was designed and fabricated by using the three-dimensional (3D)-printing technique. Second, a thin dial-a-dielectric (DaD) lens, which uses state-of-the-art artificially engineered dielectric materials for design and for which they present only the simulated results, with plans to fabricate it in the future. Both designs overcome the difficulties faced in finding desired commercial off-the-shelf materials, either for 3D-printing or for fabricating conventional GRIN lenses. The lenses comprise of several concentric dielectric rings with bespoke relative permittivities for transforming spherical waves into plane waves and vice versa. The 3D-printed thick flat lens is low-cost and light-weight, but provides broadband and high gain performance. Measurement results show that the realised gain of the thick lens is 9–11 dB over the frequency band of 12–18 GHz. The designed DaD lens has the desirable characteristics of low loss, low reflection and broadband properties.
Highlights
A lens is a well-known antenna component designed to transform a plane wave into spherical wave for focusing optical rays to a single point. It converts the spherical wavefronts emanating from a feed, located at the focal point, into planar wavefronts; and, it can be used for antenna application to realise a high directive beam
Research into a variety of flat lens antennas has been carried out based on field transformation [1]–[3], transformation optics [4]–[6], ray optics [7] and transmit array approaches [8]
The entire thick lens was fabricated in one single process without the need for machining or manual assembly
Summary
A lens is a well-known antenna component designed to transform a plane wave into spherical wave for focusing optical rays to a single point. It provides a practical fabrication approach to produce highly customisable structures with the advantages of low-cost and fast automated repeatable design and manufacturing. The expression of the required PLA volume percentage v for tailoring the effective permittivity εεrrrrrrrr of the 3D-printed dielectrics was extrapolated and given by equation (1): vv. High resolution printers with small diameter nozzles or structures with larger total volumes can achieve a lower εεrrrrrrrr. Before equation (2) can be applied to the lens design, it is necessary to know the maximum value of θmax which is determined by the diameter of the lens and the focal length. Narrow rings with small variations of volume fractions are difficult to fabricate accurately due to the resolution of this printer
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