Effect of Measurement Probe Configuration in Undermoded Nested Cavity Tests

A study of the effect of the field-sampling probe configuration used in nested-cavity measurements has been performed. The outer cavity was an overmoded reverberation chamber and the inner cavity was a small conducting enclosure that included a coupling aperture. Mechanical stirring within both the external and internal cavities was combined with frequency stirring to yield the mean received signal. Monopole, meanderline, and log-periodic probes were evaluated. The three-dimensional meanderline probes overall showed the best performance, better sampling the low-frequency signals where the inner cavity is undermoded. Despite the advantages, the mean signals levels still show a dependence on the specific configuration of the meanderline used, particularly at low frequency, and care must be used in interpreting the measured levels.