Modelling the Transient Emission from a Twin Conductor Cable
Plain language title Estimating the level of electromagnetic interference caused by
What’s it about?
Using the equations of transmission line theory, a program is developed to simulate
the response of an open-circuit line to a step pulse. This is compared with the observed
response of a twin conductor cable. It is deduced that not all of the current delivered
to the send conductor arrives back via the return conductor. Some of it departs in
the form of radiated emission.
A virtual capacitor is used to simulate this, with limited success. However, by adding
a second virtual capacitor to simulate transient current being delivered from the
return conductor back to the send conductor, a fair correlation is achieved between
theoretical and actual results. This analysis demonstrates that the return conductor
plays an active role in propagating any signal along the cable.
Why is it important?
This paper demonstrates that a circuit model can be created to simulate the mechanisms
involved in the radiation of interference from power supply cables. The analysis
can be carried out by any electrical engineer since it relies solely on the techniques
of Circuit Theory.
This is but one example of the use of circuit models to analyse electromagnetic interference.