Study on test signals for radiated immunity test in close proximity to equipment

IEC TC77 SC77B is studying a radiated immunity test in close proximity to equipment for incorporation into an IEC standard, IEC 61000-4-39. In July 2015, it published IEC 61000-4-39 2nd CD, which proposes that the test signal should be a pulse modulation wave with a 50% duty cycle in the frequency range of 385 MHz to 6 GHz. However, since actual wireless devices use different types of modulation, such as amplitude modulation, pulse modulation, and phase modulation, and may emit broadband signals, the EMI impact of wireless devices on other equipment can vary depending on the transmission method used by these wireless devices. This paper studies the test signal to be used in a radiated immunity test through experiments for cases where a 2.4-GHz band wireless device is placed in close proximity to communication equipment. The experiments have revealed that a radiated immunity test that uses only a pulse modulation wave with a 50% duty cycle as the test signal, as is specified by IEC 61000-4-39 2nd CD, can underestimate the impact of a wireless device on equipment because the immunity level of the equipment is highly dependent on the frequency used and the area to which the wave is applied.