Evaluation of frequency and mechanical stirring efficiency in a reverberation chamber

Measurements in reverberation chambers are usually performed by changing the electromagnetic environment using either mechanical or frequency stirring. Independent stirrer positions or independent frequencies provide uncorrelated fields in the cavity and thereby uncorrelated power levels. The independence of samples is necessary to make a statistical analysis of the data and provides a better accuracy of the measured parameters. The normative method has been proved to be inefficient to evaluate the number of uncorrelated samples because it uses a unique criterion which does not depend on the size of samples. This paper presents experimental results using a new method based on autoregressive models for estimating frequency and mechanical stirring efficiency. Also, we provide an experimental verification of the central limit theorem for both stirring processes, highlighting that uncorrelation does not necessarily implies independence.