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Problem with allegro PCB extraction in ADS

Question asked by y19085 on Nov 17, 2013
Latest reply on Nov 21, 2013 by volker_muehlhaus
Dear members,

I'm designing high speed ADC/DAC, and I want to extract the equivalent model of PCB to do the co-simulation.

My extraction flow is that export Allegro layout, import in ADS and do EM simulation, then using Broad Band SPICE Model Generator to have equivalent HSPICE model.

But there's some problems. Trying to simplified the problem I only layout two line with 50 ohm characteristic impedance (seen from allegro parasitic display) and the length is 34mm.

Connecting two 50 ohm resistor at each front end as Rsig and Rload, then I run some simulations. Here's some of my problems.

Problem 1.
I input DC 1.0V signal but the DC value is out of expectation, the equivalent DC resistance seems to be larger than the value from Allegro, which the voltages on each side of PCB should be close. But it is not.

Problem 2
The S21 is at higher frequency (ex: 2GHz) is so small, consequently affect the simulation result at high speed.

Problem 3
For DAC co-simulation, I input low frequency square wave (with Tr/Tf =50p or more) to see the result. But the output is obviously wrong, including the transient and stable time. Not to mention higher frequency result(ex: 2GHz).

My EM setup is 0~20GHz with 20pts, is that enough for those condition? 

I think it may be some of my option setting errors.   I really appreciate for your help. Thank you.