Common-mode currents through cables connected to printed circuit boards (PCBs) are often the dominant cause interference. Therefore, Bersier proposed in 1983 precompliance tests where a common-mode current is measured or injected though each cable attached to the equipment under test. This relatively simple method has been proven to be accurate and reliable according to many engineers. We model such a test for a PCB and describe the coupling between the signal circuits on a PCB and the circuits formed by the attached cables by means of a transmission-line approach. Demonstration PCBs with linear devices and digital logic showed that for frequencies up to about 700 MHz calculations and measurements on a 20 cm long PCB agreed within 8 dB. Keywords--- Physical Design, Printed Circuit Board (PCB) Design, EMC, Common-mode Currents. I. Introduction All electrical and electronic equipment radiates electromagnetic (EM) waves and is susceptible to external EM waves. With the increasing speed ..
