Chapter 2

Main Physical Features of Electromagnetic Cavities

2.1. Introduction

We will recall in this chapter the physical principles of reverberation chambers, partly based on the features of electromagnetic cavities. We will not recall the mathematical formulation details of the fields and of the couplings within cavities. There are many excellent books on this topic that we recommend readers consult beforehand. Instead we will take a more specific look at the behavior of the oversized cavities, cavities excited via continuous sinusoidal sources; these sources release a wavelength much smaller than their dimensions. With this purpose, the theory developed in section 2.2 will merely consist of a one-dimensional (1D) cavity made up for that reason of a coaxial line, closed at both ends by perfect short-circuits. This very simplified vision offers the advantage of analyzing the physical behavior of a common cavity, thanks to the currents and voltages coming from the transmission line theory. Thanks to this device, admittedly far from a real chamber, we reach the calculation of the eigenmodes and the assimilation of the cavity to an assembly of electric resonators made up of inductances, capacitances and conductances. This additional simplification will facilitate the rise of the quality factor concept. Its use will be essential to the physical understanding of mode stirring and other features of reverberation chambers.

Section 2.3 is the natural continuity of the previous section, ...

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