부산대학교 도서관

The last two decades have seen numerous investigations about the optimal design of mechanical stirrers for reverberation chambers (RCs), with the aim of improving their stirring efficiency, without leading to a clear consensus on the reasons for their limited efficiency. This article introduces a new criterion, by focusing on the incremental disorder introduced by mechanical stirrers, measured by their stirring coherence time, a measure of the rate of loss of coherence independent from the RC loading and excitation source. The model predicts that increasing losses would result in a loss of disorder and, therefore, of stirring efficiency. Therefore, the stirring efficiency is not limited by a stirrer being too small (electrically) or too simple-shaped, but by the limited time they have to introduce disorder in a lossy RC. Experimental tests confirm the accuracy of the model's predictions under variable loading conditions. The model can predict the maximum loading for which a stirrer can be acceptably efficient. It applies to electromagnetic compatibility testing of lossy devices, as well as over-the-air tests for wireless communication devices, where absorbers are introduced in order to emulate different propagation environments.