Prediction of Radiated Emissions From Cables with Multiple Connections to a Metal Plane

The radiated emissions from a partially shielded cable mounted 5 cm above a metal plane have been found to be dominated by the emissions from the 5 cm vertical conductor segments, which connect the cable shield and the signal wires to the metal plane at various locations. An equivalent circuit model has been developed for predicting radiated emissions from the cable. As part of an extension from the developed model, an additional wire is included and pulled back in the test setup. The methodology of modeling is applied to this new setup by adding an additional transmission line for the wire against the metal plane, and by including the mutual inductance between the transmission lines, which accounts for the locations of the transmission lines. The predicted radiated emissions match the full-wave simulated radiated emissions, further validating the modelling technique that was previously developed. This modelling procedure can be used to determine if a system meets a given radiated emission specification before any actual testing is done. If the radiation is predicted to be excessive then design changes, such as additional filtering, can be modelled before the cabling is built to determine if the changes will allow the system to meet the radiated emissions specification before testing begins.