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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.
Zhang et al. (Mon,) studied this question.