Including dielectric loss in printed circuit models for improved EMI/EMC predictions

The properties of printed circuit boards (PCBs) pertinent to electromagnetic interference/compatibility (EMI/EMC) are commonly studied using circuit models. This paper describes a method for improving these models by including the effects of frequency-dependent dielectric loss. The approach can be applied to discrete capacitors, microstrips, striplines, power buses, and power planes. The loss terms, which are expressible as frequency-dependent conductances shunting capacitors in the models, can be closely approximated over a wide frequency range as the real part of the driving-point admittance of a resistor-capacitor network. The method is applied to the important case of shunt loss conductance proportional to frequency, but other dielectric classes are as easily treated. An example power bus is analyzed for typical electrical responses, demonstrating the application of this approach, and showing the effect that frequency-dependent dielectric losses can have on the responses.