I came across this article today (more detailed paper), which claims that the widely recommended Bob Smith termination (75-ohm resistor + 1000pF to chassis GND) may not be ideal (or correct). If this is the case, why is Bob Smith termination still recommended in Ethernet design guides from Intel, TI, etc?
Is the author of the article incorrect in his analysis? Or do people just not care that the return loss could be improved with a proper choice of resistor?
Best Answer
A presentation by Royce Bohnert clearly shows that termination has no effect.
Conditions of the experiment:
Results:
Conclusions:
Picture about common mode choke integrated in Ethernet signal transformers:
All the pictures and text cited above are prepared by Royce Bohnert, the author of the referenced report.