Relation between the PCB near field and the common mode coupling from the PCB to cables

Abstract

The common mode coupling from PCB sources to cables is one of the most significant emission mechanisms. We obtain a design expression for the common mode coupling inductance of a PCB trace inside a cavity from the cavity field, which is excited by this trace. This reveals a general relation between the coupling of PCB sources to a cavity and the common mode coupling to cables. In a second step we show that the coupling of a PCB to a parallel plane cavity can be obtained from the PCB near field.