Abstract
A novel three-dimensional (3D) optical lens structure for electromagnetic field shaping based on spatial light transformation method is proposed at microwave frequencies. The lens is capable of transforming cylindrical wavefronts into planar ones, and generating a directive emission. Such manipulation is simulated and analysed by solving Laplace’s equation, and the deformation of the medium during the transformation is theoretically described in detail. The two-dimensional (2D) design method producing quasi-isotropic parameters is further extended to a potential 3D realization with all-dielectric gradient refractive index metamaterials. Numerical full-wave simulations are performed on both 2D and 3D models to verify the functionality and broadband characteristics of the calculated lens. Far-field radiation patterns and near-field distributions demonstrate a highly radiated directive beam when the lens is applied to a conical horn antenna.
Highlights
Transformation Optics (TO) concept[1, 2], known as a powerful and effective method to simultaneously control electromagnetic (EM) fields, has been widely used to exploit new classes of optical and electromagnetic devices
We introduce such a design procedure to a 3D lens with a mushroom shape that can significantly enhance the directivity of a conical horn antenna
quasi-conformal transformation optics (QCTO) is an approximate solution of minimizing the anisotropy for general boundary conditions
Summary
The conical horn antenna is modeled by a sector of radius r = 14.5 cm with its central angle chosen to be 2θ and perfect electric conductor boundary conditions are set at the two arms of the sector. In order to examine the reliability of the proposed model, simulations are performed to predict the evolutions of the electric field distribution, as shown in Fig. 3(b,c and d) at 7 GHz, 10 GHz and 13 GHz respectively. It can be noticed that in the case of the conical horn antenna alone, the wavefronts are quasi-cylindrical As it can be clearly observed in Fig. 3(b,c and d), the outgoing waves of the horn antenna in presence of the lens present planar wavefronts and a directive emission, at the three tested frequencies. The cap lens introduces negligible losses to the horn antenna, which guarantees the impedance matching of the whole system
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