Taking Into Account GTEM Field Nonuniformities in Radiated Immunity Simulations Through a Simple Measurement

When performing immunity measurements through the 10 × 10 cm aperture that some gigahertz transverse electromagnetic (GTEM) cells feature, its field uniformity is generally unknown. Yet, this (non)uniformity causes an error on test results. Measuring the field uniformity by taking a grid of samples would be time-consuming. Even with such a measurement, it would be hard to predict the magnitude of this error in immunity measurement results. Therefore, another approach to the problem was taken: several imperfections of the GTEM cell were characterized simultaneously by measuring its input reflection coefficient. Then, the immunity of a device under test was simulated with the nominal GTEM field plus the first reflection. Entering this field model into the simulation corrected the major error in the 0.1-2.0 GHz range in some of our test cases, with no degradation in any case. Thanks to the speed of this method, it may be broadly applied, even only to quantify the effect of some of the GTEM's imperfections on a given immunity measurement.