Design of an LISN for Low-Frequency Conducted Emissions Measurement

In this article, a line impedance stabilization network (LISN) with frequency bandwidth extended down to 2 kHz is designed, to address low-frequency measurement not currently aligned by the IEC and CISPR standards. For instance, different evaluation methods and limits are defined for the frequency range from 2 to 150 kHz in IEC 61000-4-7, IEC 61000-4-30, and CISPR 16-2-1. To this end, the limitations of existing LISNs for conducted emission (CE) measurement are first investigated, and a two-stage cascaded filter LISN topology is designed by resorting to multiobjective optimization. To ensure the desired performance, the influence of component tolerance and parasitic effects are studied. Eventually, an LISN prototype was manufactured and characterized. It was proven that the proposed LISN assures improved performance in terms of decoupling factor, voltage division factor, and LISN impedance in the frequency interval starting from 2 kHz.