2.4 Analytical model for the free space radiation of a cubical enclosure intended for fast predesign investigations

A fully analytical model is presented in this work for the free space radiation from a cubical metallic enclosure with a slot at one parallel-plane edge. The radiation loss is considered at the cavity field formulation by the connection of an admittance network to ports at the slot of the enclosure.
In [45] and [46] the radiation loss was calculated from the far field expressions of a cavity model without consideration of the radiation loss. Afterwards this loss was introduced into the cavity model by a quality factor. When the radiation loss becomes the dominant loss mechanism, this method fails, because the radiated power calculated from the model without the radiation loss will be far too high.
The method of this work accurately considers radiation, because the admittances are calculated independently of the cavity model.
Another modeling method for the calculation of the shielding effectiveness and wire coupling inside a cubical enclosure was utilized by [47][48][49][50]. This method models the field inside the enclosure by a superposition of rectangular cavity TE and TM modes. Wires are segmented and each segment is coupled to each TE and TM mode with mutual coupling impedances. These coupling impedances are calculated in advance. The enclosure size is not restricted in this method. However, the method cannot be generalized to arbitrary enclosure geometries.
The method of this work can deal with arbitrary parallel-plate shapes. The analytical model for the cubical enclosure is just a special case intended for first estimations in a predesign phase. Since the method in this work introduces traces only by their vertical segments to the cavity, without mode decomposition, it is more efficient and provides better insight for the optimization.

C. Poschalko: The Simulation of Emission from Printed Circuit Boards under a Metallic Cover