3D printed millimeter-wave beam-steering reflector using dielectric fluids.

A three-dimensional printed beam-steering reflector surface with dielectric fluids as the tuning agent is presented. The reflector is made using ECO-ABS with six rows of 19 parallel channels of square cross-sections. The permittivity of the ECO-ABS was measured at 2.55 with a loss tangent of 0.053. A conductor is placed at the back of the dielectric. The squared channels are filled with either distilled water or air. The effective permittivity within the reflector changes according to the material used to fill the channels. As an incident wave propagates through the printed dielectric, the configuration of air-water channels shapes the exiting phase front of the wave by locally controlling its phase delay. The resulting phase profile created by the air-water configuration leads to a steered beam. Numerical full-wave simulations show steerable angles ranging from -42∘ to 23° for a set of air-water configurations at 30 GHz. A prototype was fabricated and tested for the same configurations. Experiments confirm a wide range of angles starting at -40∘ up to 20°.

Spherical aberration in electrically thin flat lenses.

We analyze the spherical aberration of a new generation of lenses made of flat electrically thin inhomogeneous media. For such lenses, spherical aberration is analyzed quantitatively and qualitatively, and comparison is made to the classical gradient index rod. Both flat thin and thick lenses are made of gradient index materials, but the physical mechanisms and design equations are different. Using full-wave three-dimensional numerical simulation, we evaluate the spherical aberrations using the Maréchal criterion and show that the thin lens gives significantly better performance than the thick lens (rod). Additionally, based on ray tracing formulation, third-order analysis for longitudinal aberration and optical path difference are presented, showing strong overall performance of thin lenses in comparison to classical rod lenses.

Refraction in electrically thin inhomogeneous media.

This work presents a new formulation for refraction from flat electrically thin lenses and reflectors comprised of inhomogeneous material. Inhomogeneous electrically thin flat lenses and reflectors cannot make use of the Snell law since this classical formulation works solely at interfaces of planar homogeneous media. The refraction of a perpendicularly incident plane wave at a planar interface is physically explained through the phase advance of the rays within the medium. The Huygens principle is then used to construct the refracted wavefront. The formulation is validated using numerical full wave simulation for several examples where the refractive angle is predicted with good accuracy. Furthermore, the formulation gives a physical insight of the phenomenon of refraction from electrically thin inhomogeneous media.

Analytical models for electrically thin flat lenses and reflectors.

This work presents analytical models for two-dimensional (2D) and three-dimensional (3D) electrically thin lenses and reflectors. The 2D formulation is based on infinite current line sources, whereas the 3D formulation is based on electrically small dipoles. These models emulate the energy convergence of an electrically thin flat lens and reflector when illuminated by a plane wave with specific polarization. The advantages of these models are twofold: first, prediction of the performance of electrically thin flat lenses and reflectors can be made significantly faster than full-wave simulators, and second, providing insight on the performance of these electrically thin devices. The analytic models were validated by comparison with full-wave simulation for several interesting examples. The validation results show that the focal point of the electrically thin flat lenses and reflectors can be accurately predicted through a design that assumes low coupling between different layers of an inhomogeneous media.

Electrically thin flat lenses and reflectors.

We introduce electrically thin dielectric lenses and reflectors that focus a plane wave based on the principles of phase compensation and constructive wave interference. Phase compensation is achieved by arranging thin rectangular slabs having different dielectric permittivity according to a permittivity profile obtained through analytic design equations. All incident rays parallel to the optical axis converge to a focal point with equalized optical paths resulting in constructive interference. Plane wave simulations indicate strong focusing, even in the presence of impedance mismatch between free space and the dielectric layers composing the lens. We demonstrate focusing at 9.45 GHz using a lens fabricated with commercially available dielectric materials. In addition to focusing, the flat lens proposed here demonstrates relatively high power gain at the focal point. We also present a flat reflector based on the same concept. We believe that the proposed dielectric lens and reflector are strong candidates to replace heavy metallic dishes and reflectors used in a variety of applications, especially satellites.