Impact of the Symmetry of Coupling-Decoupling Networks on the Conducted Immunity Testing of PLC Modems

For conducted immunity testing, the injection of the test common mode signal is achieved by way of the couplingdecoupling network (CDN) whose symmetry is not defined in the standards. Due to the low symmetry of PLC cabling, part of the injected common mode test signal is converted into a differential mode signal that interferes with the wanted signal at the input of the modem being tested. We show in this paper that the expected bit error rates due to the differential mode current from the CDN are of the order of 1×10⁻⁵ to 5×10⁻⁵, which can be handled by coding and MAC ARQ procedures. We also show that it is unlikely that the differential mode signals from the CDN#2019;s finite LCL will overload the modems.