7. Transfer impedance

Transfer impedance is a quantity related to the insulation quality of a shield, and is fundamental to electromagnetic compatibility. The aim of this discipline is to study the causes and effects of all undesirable electromagnetic phenomena, and the means of eliminating them. We therefore study the protection of cables, circuits and systems against electromagnetic disturbances of all kinds, whether natural or man-made. In electromagnetic compatibility, there are also disturbances that come from the system itself: coupling between elements of the same circuit, or interference between antennas that are too close together. Shielding is essential for system protection. A shield's defining characteristic is its transfer impedance. This is defined by studying a plate of finite thickness. We then examine its properties and orders of magnitude.