An EMI estimate for shielding-enclosure evaluation

A relatively simple, closed-form expression has been developed to estimate the EMI from shielding enclosures due to coupling from interior sources through slots and apertures at the enclosure cavity modes. A power-balance method, Bethe's (1944) small-hole theory, and empirically developed formulas for the relation between radiation, and slot length and number of slots, were employed to estimate an upper bound on the radiated EMI from shielding enclosures. Comparisons between measurements and estimated field strengths suitably agree within engineering accuracy.