We develop a significance test that determines whether the component of uncertainty due to the finite number of stepped mode-stirring samples or the component due to the lack of spatial uniformity dominates for a particular chamber set-up and stirring sequence, as well as expressions for uncertainty for both cases. The significance test is illustrated with a measurement example comparing unloaded and loaded chambers for the measurement of a large-form-factor machine-to-machine device transmitting the W-CDMA protocol. Based on this example, we illustrate a method that allows users to estimate the minimum number of stepped mode-stirring samples needed to ensure that the component of uncertainty due to spatial uniformity dominates for a given chamber set-up, allowing use of a simplified expression for uncertainty.
Keywords: measurement uncertainty; over-the-air testing; reverberation chamber; wireless system.