Validity of Mains Cable Termination by VHF-LISN for Radiated Emission Measurement Compared with the Conventional Test Condition

In this article, we introduce an alternative terminating condition for the AC mains cable of Equipment Under Test (EUT) with appropriate common mode impedance by VHF-LISN in radiated emission measurements at test sites. In Round Robin Testing (RRT) conducted by CISPR SC-A/I joint ad hoc group 6 (JAHG6), inter-laboratory reproducibility was significantly improved by setting terminating conditions for the AC mains cable of EUT, thus, reflecting the same results as those of previous RRT conducted by CISPR/SC-I. However, since only a conventional comb generator was employed, differences in radiated emission of EUT with and without AC mains cable termination by VHF-LISN were not clear. In this RRT, we performed actual product measurement (prepared by ten participating laboratories) and compared the accumulative probability distributions of radiated emissions by using two types of VHF-LISN of different termination impedances and without a termination device (deemed as the actual operating condition). From the investigation results, mains cable termination with VHF-LISN of a specific common mode impedance was deemed to be valid for radiated emission measurement.