Abstract: An apparatus for the selective transmission or reflection of incident electromagnetic radiation. The apparatus comprises a plurality of dielectric substrates combined so as to form a stack, wherein at least two of the substrates comprise conductive elements extending in first and second directions on a surface of the substrates and at least one of the substrates includes diodes which connect adjacent conductive elements in at least the first direction. The apparatus is electronically controllable between a reflection mode and a transmission mode, wherein in the reflection mode the diodes are reverse-biased and electromagnetic radiation incident on the apparatus is substantially reflected and in the transmission mode the diodes are forward-biased and incident electromagnetic radiation is substantially transmitted.

Abstract: An integrated planar antenna-mixer device for microwave reception utilizes a slot-ring antenna and a diode quad connected thereto. The device comprises a planar metallic sheet backed on one side by a dielectric layer. A circular ring pattern is cut from the metallic sheet forming a slot ring antenna with a central disc and a surrounding ground plane. Diodes of a diode quad are connected between the central disc and the ground plane with adjacent diodes being separated by 90.degree.. The incoming microwave signal is directed perpendicular to the device plane and polarized in a direction orthogonal to a local oscillator signal similarly directed. Operation is quasi-optical without waveguides.