Experimental Results Obtained in the Vibrating Intrinsic Reverberation Chamber

Abstract

Measurements have been performed in a Vibrating Intrinsic Reverberation Chamber (VIRC). This chamber has varying angles between wall, floor and ceiling. Inside the VIRC a diffuse, statistically uniform electromagnetic field is created without the use of a mechanical rotating mode stirrer. In comparison to other reverberation chambers the VIRC displays an improved low frequency behavior, enabling faster, cost effective testing and allows for in-situ measurements. Several measurement results obtained in the VIRC are presented in this paper, such as the change in resonance frequenccy, the stirring ratio and the power density function. Introduction A reverberation chamber generally consists of a rectangular test room with metal walls and a mode stirrer, usually in the form of a large paddle, near the ceiling of the chamber. The EUT is placed in the chamber and exposed to an electromagnetic field while the stirrer slowly revolves. The average response of the EUT to the field is found by integrating the response over the time period of one revolution of the stirrer. The metal walls of the chamber allow a large field to be built up inside the chamber. The EUT is therefore exposed to a high field level consisting of several different polarizations [1,2,3,4]. The electromagnetic field inside a reverberation chamber is not time invariant as in most classic test methods utilizing free space set-ups, but provides a periodic electromagnetic environment, which is • randomly polarized, i.e. the phase between all waves is random, • spatialy uniform, i.e. the energy density in the chamber is uniform everywhere and • isotropic, i.e. the energy flow in all directions is the same. It has been shown that in a Mode Stirred Chamber (MSC) at least 200 modes should be available [3] in order to fulfill these requirements. In [6] several mode modification techniques, such as irregular walls, a moving wall and the Vibrating Intrinsic Reverberation Chamber (VIRC) have been discussed. The VIRC has vibrating walls in order to change the boundary conditions with large amplitude and short time variation. The VIRC is decribed in the next paragraph. Several tests have been carried out using the VIRC. The test set-ups and results are discussed showing the advantages of the VIRC compared to other techniques. The Vibrating Intrinsic Reverberation Chamber The VIRC is a reverberation chamber with walls made of flexible conducting material. It is mounted in a rigid structure and connected to that structure via flexible rubber strings, as shown in Figure 1, and drawn schematically in Figure 2. By moving one or more ridges or one or more walls the modal behavior of the field inside the chamber is changed, and thus the resonance frequencies are changed. Because this frequency shift is much larger compared to what is possible with a conventional mode stirrer, the frequency range of the chamber is extended to lower frequencies compared to a reverberation chambers with equal dimensions. Note the natural corrugation of the flexible walls in Figure 1, which is beneficial for the spatial uniformity too. Another advantage is that the flexible chamber can be erected inside a standard anechoic chamber where the EUT has been installed for standard EMI tests, thus reducing measurement time and cost. Furthermore the VIRC does not need extra space inside the laboratory: it can be folded and put away fast. The most important advantage of the flexible structure of the VIRC is that it can be installed in-situ. Figure 1: The Vibrating Intrinsic Reverberation Chamber hanging in strings

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Cite this paper

@inproceedings{Leferink2004ExperimentalRO, title={Experimental Results Obtained in the Vibrating Intrinsic Reverberation Chamber}, author={Frank Leferink and Jean-Claude Boudenot and Wim van Etten}, year={2004} }