Modeling of complex field inside chaotic Electromagnetic reverberation chambers
Résumé
Electromagnetic reverberation chambers (RC) are nowadays commonly used for electromagnetic immunity testing applications. Thanks to the presence of a mechanical stirrer (generally a rotating metallic object), electronic devices under test are submitted to an isotropic, statistically uniform and depolarised electromagnetic field. The latter features of the field can be obtain as long as the frequency is above the so-called lowest useable frequency (LUF). We can note that the statistical requirements of a well-stirred RC above the LUF closely correspond to the natural behaviour of a chaotic cavity, of course without the help of any stirring process. We propose to use the universal properties of chaotic cavities to reduce the LUF. We present a numerical investigation of three-dimensional electromagnetic chaotic (Sinai- like) cavities. We computed around 600 eigenmodes for two different geometries: a parallelepipedic cavity with one half-sphere on one wall and a parallelepipedic cavity with one half-sphere and two spherical caps on three adjacent walls. In these cavities we show that the statistical requirements of a well operating reverberation chamber are better satisfied in the more complex geometry due to its spatial and spectral statistical behaviours very close to those predicted by random matrix theory. More specifically, we show that in the range of frequency corresponding to the first few hundred modes, the suppression of non-generic modes can be achieved by reducing drastically the amount of parallel walls. Finally, we model and compare the influence of losses on the statistical complex response of the field inside a parallelepipedic and a chaotic cavity.