Creation of a gradient index structure inside foam material - Microwave application for a lens antenna at 60 GHz

Creating a gradient index into a dielectric structure is a major issue nowadays for the design of microwave components and antennas, especially for inhomogeneous 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 Luneburg lens antenna at 60 GHz.