Formula for the Field Excited in a Rectangular Cavity With an Aperture and Lossy Walls

A formula is derived for the field excited in a rectangular cavity with lossy walls by an external field acting on an aperture in a wall. The formula is used to calculate the energy density shielding effectiveness (SEU) of a lossy cavity. The calculated SEU is shown to be in good agreement with results derived elsewhere for the SEU of lossy cavities.