Using autoregressive models to estimate the number of independent samples available with stirrer rotation in reverberation chamber

In reverberation chambers (RC), measurements are often performed by selecting samples using the rotation of the mode stirrer. The number of independent samples is the number of stirrer positions that give uncorrelated field in the cavity, and thereby uncorrelated power levels. A larger number of samples provides a better accuracy of the measured parameter. To determine the number of independent samples, contradictions were already highlighted about the normative method using the autocorrelation function (ACF) with the criterion 0.37. Calculating the number of independent samples remains a great challenge. This paper proposes a new method based on autoregressive (AR) models and central limit theorem (CLT) to find the number of independent samples available with stirrer rotation. The simplicity of implementation is demonstrated and experimental validation is provided.