Fundamental Properties of Non-cuboid Reverberation Chambers

摘要

Electromagnetic reverberation chambers were proposed in 1968 by Mendez [8] and have been discussed as possible ways for radiated immunity and emission tests since then. Continuous use lead to demand for standardization, which was covered by the publication of the IEC standard 61000-21-4 [2] in 2001. Since electromagnetic reverberation chambers were developed to replace semi-anechoic chambers or open area test facilities for testing of large scale DUTs, most of the, initial research was devoted to large cuboid chambers. Yet, if a smaller chamber is needed (for lack of lab space, for example) or if the use of (expensive) amplifiers is to be avoided, the IEC standard will provide only suboptimal information for this. Furthermore, the possibility to use other geometrical bodies was not yet investigated in depth. Some of the cavity resonators that could be used as a basis for reverberation chambers have a better surface to volume ratio and thereby promise to have a higher quality by default. Additionally, is to be expected that the superposition of different resonant modes will result in larger test volume (read: volume in which fields are homogenous and evenly distributed w.r.t direction and polarization), since the directions of the fields inside a noncuboid volume will be irregular. Therefore, it should be possible to reduce the size of the chambers even more. In this paper we first discuss a relatively small cuboid cavity which we will use as a reference. Then we review chambers based on cylinders with circular and elliptic cross sections, spheres, and finally scalene ellipsoids. For these bodies, eigenmodes and eigenfrequencies are calculated numerically and analytically (if possible). The mode densities and qualities are determined.