Electromagnetic Reverberation Chambers

Chapter 3

Statistical Behavior of Stirred Waves in an Oversized Cavity

3.1. Introduction

Chapter 2 reached the conclusion that the field distribution observed in an electromagnetic cavity was hard to predict when its dimensions were much higher than the wavelength. The theoretical difficulty mainly comes from the presence of scattering devices. We can add to these geometrical details the energy losses. Their contribution manifests itself in the appearance of groups of modes, whose relative intensity depends on the lesser displacement of the transmitting antenna immersed in the chamber. If the calculation of the field remains possible using theoretical simulations adapted to the context of the MSRC, the use of these numerical models is extremely costly in computer resources. All of these reasons have thus encouraged scientists to compare the electric or magnetic fields with random variables. We will try to add to these variables probability density functions and statistical properties, all examined in this chapter [KOS 91, SER 09].

Section 3.2 is devoted to the statement of the postulate specifying that the distributed field in a perfect MSRC answers to the largest random behavior. This means that under continuous sinusoidal excitation, the complex components of electric (or magnetic) field variable appropriate the conditions of maximum entropy and minimum energy. This reasoning leads to the normal probability density function (pdf), while assuming an isotropic field distribution. ...