Experimental investigation of the number of independent samples and the measurement uncertainty in a reverberation chamber

Due to the complicated and time-varying boundary conditions, reverberation chamber (RC) measurements are usually studied using statistical analysis. Hence, it is of importance to know the number of independent samples of the measurements. Different methods for estimating the number of independent samples has been proposed in the literature. This paper uses the spatial degrees of freedom method to estimate the independent sample number. Comparing with the commonly used autocorrelation function method, the proposed method requires less computation time and provides a smaller estimation bias for correlated samples and a smaller estimation variance once above a certain sample number. The estimated independent sample number can be used to explain the dependences of the measurement uncertainty on frequency, mode stirrers, and RC loading. Finally, the estimated independent sample number is used to predict the standard deviation (STD) of the average power level for different loading configurations, where good agreements are observed.