The interface between a multi pin connector and the printed circuit board (PCB) is a critical part of the signal path in high speed digital systems like mainframe computers. Long range via coupling effects are analysed for connectors with a huge signal count and high speed signals using CST MICROWAVE STUDIO® simulations. A realistic cross section of the PCB with a mixture of ground and voltage layers has been taken into account. It was possible to understand the reason for the behavior by analyzing the field distributions during the signal propagation inside the PCB. A further important result was the calculation of the magnitude of the distortions to judge their impact on the signal integrity of a complete system. Finally, the long range crosstalk effect was verified with time domain measurements on a specially designed test card system.
Thomas-Michael Winkel, Roland Frech (IBM Entwicklungs GmbH); Thomas Gneiting (AdMOS GmbH)