Effect of local stir and spatial averaging on measurement and testing in mode-tuned and mode-stirred reverberation chambers

The effect of local averaging in mode-tuned and mode-stirred reverberation chambers is investigated, under the assumption of a wide-sense stationary statistical cavity field. The analysis is based on the characterization of the tuning or stirring process in the spectral spatial domain and in the spectral stir domain. The variance function, scale of fluctuation, optimum sampling rate, and normalized spectral bandwidths are computed for each case, based on the modeled power spectral-density function. This second-order analysis enables the effect of local averaging on the point-interval correlation, mean and standard deviation of the maximum test level, upward threshold crossing frequency, time to first passage and mean excursion length to be quantified. The theoretical results for quantifying EUT reliability are illustrated and compared with measured data. The results provide guidelines for the maximum tolerable sensor aperture and stirrer step sizes for mode tuning, and sampling rate and sampling width for mode stirring in chamber calibration and EMC emissions and susceptibility testing.