On the measurement of shielding effectiveness in a mode stirred chamber

In the work presented here, the authors investigate how the isotropic shielding effectiveness measured in a mode stirred chamber (MSC) varies with probe type and position for a generic avionics bay. The measurements are made using six different probes in six positions. In the analysis, the measured received power is compared to the theoretical exponential distribution with good agreement for the entire frequency range, from 400 MHz to 18 GHz. Using confidence intervals, the authors show that for a given probe, shielding effectiveness is not independent of position. Indeed, the measured isotropic shielding effectiveness can vary with more than 10 dB between positions. The possible reason for these somewhat surprising results is assumed to be caused by leakage from one dominant unintentional aperture of the generic avionics bay.