An approximate theory of RF shielded enclosures

Shielded enclosures are important components of modern electronic systems and devices. They are often used to provide needed RF isolation between a device and the environment; they appear simple, almost trivial, yet they have subtleties that are often misunderstood. This paper uses simple physical concepts to explain the operation of shielded enclosures and derives equations that may be used to estimate their performance. Measured data that supports both the assumptions and the results of the paper are also presented.