Application of the optical black-hole principle to the estimation of shielding effectiveness to radio frequency energy

The interior of a typical shielded enclosure is usually densely filled with interconnected electronic subassemblies each contained within its own shielded container and pretested to have a specified shielding effectiveness in a free-space environment. The problem of estimating the overall shielding effectiveness when these subassemblies are placed inside the shielded enclosure is discussed. An optical black-hole (i.e. reflectionless aperture) principle is used to obtain estimates (within 10 dB) of the shielding effectiveness of enclosures having dimensions that are large compared to a wavelength. Empty enclosures are considered, as well as enclosures filled with subassemblies, groups of which are characterized as domains. Formulas are given for cavity buildup for an empty enclosure and for an enclosure containing a domain comprising of a cable between two subassemblies. A limiting case is discussed for which this approach may not apply