Knowledge of the shielding effectiveness of an enclosure is important for the electromagnetic compatibility of electronic systems. The shielding effectiveness of an enclosure depends on the absorption cross section of its contents. It might be expected that the energy absorption in an electronic circuit changes according to the operating state of the semiconductor devices which compose the active components. In most published research, the absorption cross section measurements were performed when the contents were unpowered. In this paper we compare the measured absorption cross sections of the components of a personal computer in powered and unpowered states. Comparisons indicate that power and the particular operating configuration do not have a significant influence on the absorption cross section. This means that the process of determining absorption cross sections of circuit boards and other components can be easily achieved without the need to provide power and define a particular operating state.
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