Characterization of the maximum test level in a reverberation chamber

Among the significant characteristics of the electromagnetic environment in a reverberation chamber are isotropy, random polarization and uniformity. These characteristics permit robust immunity testing without moving the equipment under test or the field generating antenna. These characteristics have been repeatedly demonstrated for frequencies where the chamber is highly overmoded. In this case, the statistical electromagnetic test environment can be described in terms of a chi-square distribution. However, the maximum value of the test environment, which is generally the parameter of most interest for immunity testing, is a random variable. Thus there is a potential for an under or over test of the equipment under test. This paper discusses the distribution function for the maximum to mean ratio for an overmoded reverberation chamber. The paper addresses the expected value of the maximum to mean ratio and the uncertainty in the ratio for a given level of confidence. The paper also compares the theoretical predictions to experimental data.