Method and apparatus using photoresistive materials as switchable EMI barriers and shielding

摘要

A method and apparatus for providing a switchable electromagnetic interference (EMI) barrier. The method protects an object against electromagnetic radiation, through the steps of: providing an object to be protected from electromagnetic radiation; placing a barrier sheet adjacent to the object, the sheet being opaque to radiation when exposed to light; directing the light against the sheet when a barrier to the radiation is desired; and extinguishing the light when passage of the radiation through the sheet is desired. One embodiment is a switchable electromagnetic radiation barrier system that includes a photoresistive sheet interposed between a source of electromagnetic radiation and an object to be protected from the radiation. This sheet is opaque to the radiation when exposed to light of a selected visible intensity range. A light source adjacent to this sheet directs the light against the sheet. A second embodiment is an apparatus for protecting an EMI-sensitive device in an air vehicle from external electromagnetic radiation (EMR). The apparatus includes: a cavity in an air vehicle; an EMI-sensitive device in the cavity; and a barrier window covering the cavity. The window includes a support sheet having a layer of photoresistive material. This material transmits EMR when exposed to light and does not transmit EMR when unlighted. A light source is provided to selectively illuminate the layer. Another embodiment is an antenna element of layered sandwich construction, including a polyimide film layer. Switchable means are used in the embodiments to turn the light source off and on.