Automated system for electromagnetic field generation and immunity testing

An interactive computer-controlled system has been constructed for radiated immunity measurements. It can set up a desired unperturbed field at a point in space and simultaneously measure field strengths and polarizations at up to ten different positions. Field mapping experiments have been performed with the system in an anechoic chamber, a partially loaded shielded room, and an unloaded shielded room. The results confirm a considerable improvement in spatial field uniformity as more absorber is used. If the unperturbed fields in a specified test volume do not deviate more than a desired amount for any frequency of interest, an equipment under test (EUT) can be placed in the test volume and its response to radiation measured using current probes and a spectrum analyzer. Such an experiment requires many midexperiment calculations, so that automation results in significant time savings. Measurements have been made in the range from 50 to 200 MHz, which previously has been a different band in which to perform immunity measurements. This measurement system can be used in conjunction with many other facilities, such as TEM cell, an open field site (ground screen) or a reverberating chamber, and can be used to test at frequencies from the low kilohertz region to 2 GHz