Experimental extreme field strength investigation in reverberant enclosures

The field strength distribution in real reverberant enclosures, such as plane fuselages or factory interiors, is often too complex for a deterministic approach but can also fall into a category where theoretical assumptions normal for perfect cavities no longer hold. It can vary a lot depending on the actual environment. Estimation of the extreme peak value in real reverberant enclosures is of utmost importance for Electromagnetic Interference (EMI) in terms of either in-situ measurements or EMI threat analysis. It is very difficult to measure it on-site due to usually a low number of available samples. However, as long as these are multipath environments, the peak values can be estimated within a certain confidence based on the average field strength, which can be measured much simpler. In this paper, the maximum-to-average electric field ratio was experimentally analysed in three configurations of two Vibrating Intrinsic Reverberation Chambers (VIRC), simulating the real reverberant environments with different mode densities obtained either by scaling the enclosure in terms of physical or electrical size. In each configuration the influence of the chamber loading, and therefore the quality factor, was analysed in at least 7 steps as a parameter relating the enclosures to each other. 1 hour long measurements were conducted taking samples every 10 ms in each setup, exploiting the randomness of the chamber and allowing for high repeatability of results.