The Effect of Noise on Reverberation-Chamber Measurements of Antenna Efficiency

In this work, we show that high antenna frequency selectivity can make it more challenging to accurately measure antenna efficiency in a reverberation chamber (RC) when using the two-antenna method since electronic noise can affect the measured stirred-energy component of the S-parameters. Recognizing whether the measured antenna-efficiency estimate is significantly affected by electronic noise is not trivial. The measured S-parameters used for calculation may have high signal-to-noise ratios (SNRs), but the antenna-efficiency estimate can still show large systematic errors due to noise. We model noise as a component of the measured stirred energy, showing that the measured reflection is much more susceptible to noise than the measured transmission. We do not focus on the origin of the noise, but rather on the effect it has on the measurement. We show the effect of noise on the overestimation of the stirred energy components of the S-parameters, which affects the two-antenna formulation more significantly than the three-antenna method one. We show that this overestimation can cause efficiency estimates calculated with the two- and three-antenna methods to be significantly over- or under-estimated and we show that uncertainties increase as well. Finally, we provide clear steps to recognize and reduce noise effects in antenna efficiency measurements.