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simulating 100R differential lines with EM/Sonnet

Question asked by mlabro on Apr 11, 2005
Latest reply on Apr 30, 2005 by ROB_LEFEBVRE
For ethernet switch, I need to use 5cm (Tx+,Tx-) and (Rx+,Rx-) 100R lines.

Suppose I draw in layout two 15 mils wide, 2000 mils long, microstrip lines separated with a 10 mils gap on a 62 mils fr4 substrate.

1. Could you please tell me how we can put ports and configure EM/Sonnet to compute Zcommon (50R expected when widthes/spacing are correctly computed) and Zdifferential (100Rexpected) and display these on graphs ?

2. Computing mathematically widthes and spacing are hard to do. We need special expensive softs (Quick solver...) to do that. Do you think it is possible to draw arbitrary values (15,2000,10 mils) optimize these until Zcommon and Zdiff are the expected 50R and 100R values ?

A wsp would be appreciated.