Experimental Evaluation of the Statistical Isotropy of a Reverberation Chamber’s Plane-Wave Spectrum

Synthetic-aperture measurements in a loaded reverberation chamber are used to calculate power-angle profiles describing the instantaneous distribution of received power versus azimuth angle-of-arrival. Averaging multiple power-angle profiles leads to estimates of the reverberation chamber´s power-angle spectrum. A comparison to simulated power-angle spectra for an ideal reverberation chamber indicates that the loaded reverberation chamber tends to provide a statistically anisotropic plane-wave spectrum. Analysis of the measurements´ power-delay-angle profiles suggest that this anisotropy due to both the presence of unstirred multipath components and strong early-time stirred multipath components arising from reflections off of the mode-stirring paddles´ planar surfaces. Guidelines are provided for minimizing the effect of a statistically anisotropic plane-wave spectrum, such as the use of additional stirring mechanisms and minimizing the contributions of unstirred multipath components.