The Effect of Peripheral Equipment Loading on Reverberation-Chamber Metrics

Measuring wireless devices in a reverberation chamber often requires ancillary equipment to be present in the chamber. This paper illustrates the effect of their presence on metrics that are important in wireless device tests, such as chamber decay time, coherence bandwidth, and antenna efficiency calculations. The results show decreases in chamber decay time of approximately 20 % when power supplies and power cords are present in the NIST chamber. For the chamber studied, the effect is approximately 10 % with a regular power cord, demonstrated to be mostly caused by the copper conductors through measurements and a model of the cord insulation. The effect on antenna efficiency by using a predetermined time constant is shown to be between 5 % and 10 % for different setups. Results from two reverberation chambers are presented, showing lower percentages for a chamber with higher losses.