Abstract: A system for selectively blocking electromagnetic energy. The system includes a first mechanism for employing a perforated component to pass a beam characterized by a first property and reject a beam characterized by a second property. A second mechanism selectively alters a beam passed by the first mechanism so that upon reflection, the beam exhibits the second property. In a specific embodiment, the first property corresponds to a first polarization, and the second property corresponds to a second polarization. In the specific embodiment, the perforated component includes a beamsplitter having a first perforated metallic plate. The second mechanism includes a quarter-wave plate having a second perforated metallic plate.

Abstract: A biconical antenna having fully adjustable design parameters. The biconical antenna has a coaxial feed having outer and inner conductors. A lower support structure secures a lower cone to the outer conductor. An upper support structure secures an upper cone to the inner conductor. A dielectric window support is disposed between the lower and upper support structures. To make the antenna relatively lightweight, each cone may be made of sheet metal plates that are connected to the lower and upper cone support structures. A reservoir is formed within the upper cone. Dielectric material, such as oil, is disposed within the antenna. Air bubble escape holes are disposed in the upper support structure so that air bubbles that are formed at the coaxial feed can escape to the reservoir. The holes do not allow electromagnetic power leakage between the coaxial feed and the reservoir, and the position of the holes is such that the air bubbles rise from the coaxial feed into the reservoir.