Transfer impedance measurement of a 19"-subrack

The transfer impedance of a 19"-aluminum subrack has been measured by injecting a current into the shield surface and measuring the voltage across the inner surface between the injection points. The measurements were performed in the frequency range from dc up to 30 MHz. With two different set-ups, the influence of the current return path was examined. The surface transfer impedance depends strongly on the mounting conditions of the basic unit (side plates and horizontal rails) and the covers. The interference currents were symmetrically injected into opposite shield surfaces in x, y and z-direction.