A PROPOSED METHOD FOR QUANTIFYING UNCERTAINTY IN RF IMMUNITY TESTING DUE TO EUT PRESENCE

Abstract

Throughout the performance of a RF immunity test according IEC 61000-4-3 there are several factors that should be taken into account to ensure the quality and to estimate the uncertainty associated to the results. One phenomenon that should be considered to calculate uncertainty is the disturbing efiect produced by the EUT over the electric fleld generated within the calibrated uniform fleld area; nevertheless the mentioned efiect is not easily quantiflable because the measuring process using additional antennas or fleld probes inside the semianechoic chamber could also alter the electric fleld distribution. An experimental method for quantifying the mentioned uncertainty contribution is presented. The method is based upon the fact that antenna-EUT coupling and re∞ection efiects could be measured through changes in the input impedance of the fleld generation antenna. A validation procedure for the proposed method is also described. Hence, a relationship between the re∞ection coe-cient at the antenna input port and the electric fleld strength is derived. The uncertainty contribution is calculated through the maximum relative change in the E-fleld intensity magnitude for the frequency range of 80{1000MHz, considering the worst case for several EUT positions.