Study on test distance between EUT and antenna for radiated immunity test in close proximity to equipment

IEC Technical Committee TC77 Subcommittee SC77B is studying a radiated immunity test in close proximity to equipment for incorporation into a new IEC standard, IEC 61000-4-39. Although IEC 61000-4-39 2nd CD, which was published in July 2015, requires that the test distance between equipment under test (EUT) and a test antenna be 100 +/- 5 mm at a frequency range of 385 MHz to 6 GHz, whether this test distance is valid for such a wide frequency range requires additional study. This paper attempts to validate the test distance for a radiated immunity test under the assumption that a 2.4 GHz-band wireless device is used in close proximity to telecommunication equipment. Three antenna candidates were used to examine how the size of the uniform electric field strength to the EUT varies when the test distance is changed. We also examined how the electric field strength near the test antenna affects the appropriate test distance for the case where the side surfaces of the EUT are shielded by metallic conductors. Furthermore, we studied how varying test signal types in a radiated immunity test affects the appropriate test distance and consequently the EUT.