(Color online) The simulation model, in which Circle I is composed of regions II and III, while Circle II is made up of regions I and II. The two circles have the same size (R = 30 mm), and their centers have a distance of d (d = 14 mm in our setting).
(Color online) The 2D simulation results using COMSOL at 10 GHz. (a) Circle I is rotated by 90° to the left. (b) Circle I is rotated by 45° to the left. (c) Circle I is not rotated. (d) Circle I is rotated by 45° to the right. (e) Circle I is rotated by 90° to the right.
(Color online) The 2D simulation results of the far-field radiation patterns using COMSOL.
(Color online) The distribution of the refractive index of the special Luneburg lens. The minimum index is set as 1.1, which is determined by the drilling-hole composite materials. Here, different dielectric plates are used in Areas I and II to satisfy the requirement of the refractive index distribution.
(Color online) (a) The simulation environment setting in the CST Microwave Studio. (b) The relations between the refractive index and the drilling-hole’s diameter, D. Two different dielectric units based on F4B are shown at 10 GHz. The sizes of (a) and (b) are 2 × 2 × 2 mm3 and 2 × 2 × 1.2 mm3, respectively.
(Color online) The 3D CST simulation results of the entire model (special lens plus Vivaldi antenna) at different frequencies: (a) 8 GHz, (b) 9 GHz, (c) 10 GHz, and (d) 11 GHz.
(Color online) The fabrication of the special Luneburg lens and the Vivaldi antenna. (a) A large composite material plate with a radius of 30 mm is composed of inhomogeneous 2 × 2 × 1.2 mm3 unit cells. (b) A small metamaterial plate with a radius of 9 mm is composed of inhomogeneous 2 × 2 × 0.8 mm3 unit cells. The 2 × 2 × 2 mm3 unit cells can be achieved by adhering two such unit cells. (c) The constructed special Luneburg lens composed of several layers. (d) The designed Vivaldi antenna. (e) The combination of the special lens and the Vivaldi antenna. (f) The side view of such a device and the height of the lens is equal to 10 mm.
(Color online) The measured far-field radiation patterns of the fabricated sample (special lens plus Vivaldi antenna) at different rotation angles; (a) 8 GHz, (b) 9 GHz, (c) 10 GHz, and (d) 11 GHz.
(Color online) The beam scanning based on the Luneburg lens.
(Color online) The COMSOL simulation results at 10 GHz. (a) The schema of the simulation model. (b) The near field radiation result when d = 5 mm, (c) d = 8 mm, (d) d = 11 mm, (e) d = 14 mm, (f) d = 17 mm, and (g) d = 20 mm. (h) The near field radiation result with the normal Luneburg lens. (i) The near field radiation result of the Vivaldi antenna.
The measured gain and HPBW of the antennas.
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