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Problem in S- parameters simulation at trace thickness 7 um.

Question asked by mukulratwani on Mar 1, 2015
Latest reply on Mar 3, 2015 by volker_muehlhaus
Hello all, 

               I am simulating S-parameters for  chip on board(COB) testing system.  Specification of the PCB parameters are as follows: 

1. Dielectric constant = 4.4 (Mitsubishi material)
2. loss tangent = 0.006
3. PCB thickness = 0.25 mm (0.001 inch)
4. Trace thickness(height) = 7um

The trace layout  png image is also attached.  I am running simulations from 100 Mhz to 25 Ghz.   Results obtained from layout window  were collected and re-simulate it in schematic window using differential configuration.  Testing mechanism is also attached. But it is showing some weird results. S11 should be good at 100 Mhz. It is showing S11 at 100 Mhz is -1.16 dB.  Simulations are perfectly fine when I was running  at Trace thickness 35 um.  I recalculate all dimensions at 7 um, but at 7 um result was not fine. 

Can anybody help me to find out the reason why at 7 um results are not fine.  

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