The influence of positioning tables on the results of radiated EMC measurements

Radiated electromagnetic compatibility (EMC) tests usually apply a positioning table in the test zone of the EMC facility. The equipment under test (EUT) is positioned on this table as prescribed by EMC standards. The EMC standards implicitly assume that the influence of the table is negligible as long as such a table complies with the qualitative specification in the standard. In view of the work associated with the uncertainties of EMC standards, the influence of the positioning tables is investigated for both radiated emission and immunity testing. Measurement results and simple simulations demonstrate that the impact of a 'nonconductive table' may be significant. Requirements for positioning tables should therefore be incorporated in emission and immunity standards.