METALLIZED FOAM MAY be a way to reduce antenna manufacturing complexity and cost. For example, a microstrip-patch antenna embedded in a rectangular cavity, inspired by the Koch island geometry, has all metallic parts (patch, cavity, and feeding probe) metallized on foam. This work was conducted by Jaume Anguera, Carmen Borja, Josep Mumbr, and Carles Puente from Fractus (Barcelona, Spain) together with Jean-Pierre Daniel and Tiphaine Leduc from Advanten (Rennes, France) and Nancy Laeveren and Peter Van Roy from Emerson & Cuming Microwave Products (Nijverheidsstraat, Westerlo, Belgium).

Metallized-foam technology can be used to design structures that are lightweight, flat or conformal, and low in cost. Such structures also may be arbitrary shaped, as is the case with fractal geometries, using electromagnetic-bandgap and other advanced materials. The materials are formulated according to a required dielectric constant. Yet the foaming process also is critical because the expansion and gelation of the foam must be balanced for controlled cell formation. Such variations in foam properties can arise from the chemistry of the formulation.

The researchers' main objective was to achieve direct metallization of the foam rather than a metallic film applied on a previously machined convex foam surface. Their technique offers the possibility of three-dimensional metallized shaped surfaces including arbitrary metallized shaped holes (rectangular, circular, etc.) and via holes. To get a deposit of metal over all of the surfaces in the contact, this approach immerses the object in different saline solutions. Compared to a standard fabrication process, the researchers found that far fewer pieces were needed to construct their antennas. See "Metallized Foams For Fractal-Shaped Microstrip Antennas," IEEE Antennas & Propagation, December 2008, p. 20.