Creation of a gradient index structure inside foam material for an Inhomogeneous lenses with focusing and beam scanning capabilities in millimeter waves

The presentation deals with inhomogeneous dielectric lenses which allow to focus energy from one primary source (antenna). The index law inside the lenses give the opportunity to design beam scanning and beam shaping antennas. Creating a gradient index into a dielectric structure is a major issue nowadays for the design of microwave components and antennas, especially for lenses as Luneburg, Fresnel and Maxwell Fish-eye. The use of a foam material and a simple technological process can allow this. Because a foam material is composed of air bubbles, and core materials (resin, PVC ...), removing the air will increase the density of the foam and so increase its dielectric constant. The authors present a simple technological process to expel the air from a piece of foam in order to increase the permittivity of the foam. This is then applied to the design of a various kind of lens antenna in millimeter waves. The authors worked on this type antenna for millimetre wave applications such indoor communication systems at 60GHz of automotive radars at 24 and 79GHz. The presentation will be divided in sub parts as: How to reconstruct the index law inside the lens? Which type of primary source to illuminate the lenses? Beam scanning and beam shaping capability; Example of 60GHz active lens antenna.