Cavity Model for the Slot Radiation of an Enclosure Excited by Printed Circuit Board Traces With Different Loads

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

“…The coupling from a trace, like in Fig. 5, to the cavity field is considered with two ports in (6) according to [4]. One port at the source position so of the trace and a second port at the load position lo of the trace.…”

“…RELATION OF THE PCB NEAR FIELD TO THE CAVITY FIELD In Section II we described the relation between the cavity field and common mode coupling to cables. Only the vertical current segments of a trace couple to the cavity, according to [4]. High currents on PCB traces and ICs are identified from a near field magnitude scan.…”

“…Since the common mode coupling of a PCB trace to cables depends on the trace geometry and the trace position on the PCB and not only on the trace current magnitude, critical areas on the PCB cannot generally be assigned to areas with increased near field magnitudes. In Section II we obtain the common mode inductance L cm for a PCB trace inside a parallel plane cavity from the cavity model of [4]. We verify this L cm with measurements and a comparison with the common mode inductance formulation for parallel planes of [5].…”