Insertion of Guard Band to reduce cross talk

Let us assume that two traces have been routed in parallel to each other. The width of the traces are 5 mils and they are separated at 5 mils apart. Calculations showed that this gave rise to a cross talk of 12% for a height of 10 mils above ground. Guard traces are recommended to reduce the cross talk between the traces. To insert 5 mils guard trace the two traces have now to be separated by 15 mils. In the 15 mils gap between the traces, 5 mils guard trace has been inserted. The cross talk problem was reported to have been solved. The fact is, increasing the separation between the traces from 5 mils to 15 mils significantly reduces the cross talk anyway. Calculations show that increasing the trace separation from 5 mils to 15 will reduce the cross talk from 12% to 2%.

While the guard band does further reduce the crosstalk, the incremental gain is not substantial. Most of the gain is achieved by increasing the separation.

Previous                    Next