Conducted Emission Measurements with a CDN Showing Very High-Frequency Component Effects in a Synchronous Buck Converter

Modern high-frequency power electronic converters consisting of smaller-sized components composing higher switching frequencies are more prone to noise emissions into the Very High Frequency (VHF) band.Pre-compliance conducted emission testing can be performed in the development laboratory with a Line Impedance Stabilising Network (LISN) that can be constructed and calibrated. As most conducted Electro-Magnetic Compatibility (EMC) tests are performed up to 30 MHz, and some only to 10 MHz, conducted noise emissions beyond this band are not intended to be verified with the standard LISN. If the pre-compliance conducted emission design verification performed in the development laboratory can include the higher frequency bands, well within the VHF frequency range, a more thorough pre-compliance verification can be performed in the development laboratory that can show possible radiation effects.In this paper, we investigated replacing the LISN with a Couple-Decouple Network (CDN) for performing VHF-band conducted emission testing, showing VHF power converter noise phenomena. The CDN sensitivity is demonstrated by showing the UHF effects of a toroidal inductor orientation placement in a two-phase buck converter.