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Transient simulation of nport (s-par) in spectre cadence

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fathi

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spectre transient simulation time s-parameter

I have s-parameter data exported into Cadence, and used in nport component. Depending on whether I choose windowing=yes or windowing=no, or set the maximum frequency limit for the n-port, or using equivalent y-parameter or z-parameter instead of s-parameter, I either get error in transient simulation (Signal V(...) = 1.3 GV exceeds the blowup limit for the quantity `V' which is (1 GV). It is likely that the circuit is unstable. If you really want signals this large, set the `blowup' parameter of this quantity to a larger value.) or get different result which are not consistent with each other. The component whose s-parameters I'm using is not passive. Any suggestion for the setting or overcoming this issue?

Thanks.
 

z-parameter data file spectre

If it is an active device S-parameters, it is not possible to simulate transient with S-par.
The S-parameters measured for particular bias point, where the circuit is assumed linear with small signal variations.
I've heard about P2D S-par, may be you can use it...
 

cadence error blowup limit

I'm sorry, my mistake; the architecture is passive. It's not active.
 

blowup limit spectre

So use Spice model generator tools in ADS to get lumped elements spice model for transient simulations.
 

cadence blowup parameter

Thanks for your reply.

1- I tried fitting a Pi-Lumped Network Model (which would physically be able to describe the behavior of my block across a narrow frequency range) in a narrow frequency range using ADS Spice Model Generator, but the generated/predicted S-parameters of this lumped model are very different from the original S-parameters, and as a result, the simulation result of the circuit is not right.

2- I simulated the same circuit using S-parameters (SNP compoenets) in ADS, and got consistent result for transient simulation there. So, basically, there should not be any problem in time-domain simulation using S-parameters. I am not probably using the right settings in Cadence.
 

s-parameter passivity check cadence

You have to adjust the Pi model after generation with optimization tools in order to match the result with S-par and Pi model.
 

s-parameter spectre dc

For transient simulation, you have to set your n-port in your CDF to spline in the interpolation method. It is better if you can carefully modified your .s2p file such that there is a zero freqeuncy data
 
spectre s model view cadence

How would you set it up in ADS to find the components?

I couldn't find any element in ADS for matching the S-parameters. The way that I set it up is that I put the S-parameter data as a n-port device (SNP) and I put the schematic of the lumped model to fit with n additional ports in the same schematic. So, I have a schematic with total of 2*n ports. Then, I set the goals to be magnitude(Sij)=magnitude(S(i+n)(j+n)) and phase(S(ij))=phase(S(i+n)(j+n)). I tried satisfying these goals by setting the RELATIVE error be smaller than 1%, but that causes a problem around zero phase, not mentioning the 2pi discontinuity points. Finally, I couldn't make it converge to a good result. Do you know any standard and robust way of fitting the model to a given s-parameter data in ADS?

Thank you very much.
 

spectre s-parameter transient

I do it by hand with parametric simulation.
 

s-parameter file in spectre dc block

I don't get your method.
If the number of ports are large and/or the model has many compoenents, it's not possible to find the values by hand.
 

s parameter simulation spectre cadence

Yes, you are right. I did it for spiral only...

Added after 13 minutes:

Have you tryied the method milkdragon suggested? If it works inform me pls. I'm intrested in this problem also.
 

s2p spectre transient

Based on the nport application note from Cadence, linear interpolation usually works better than spline. By zero frequency, you mean resonance frequency? I even increased the frequency range to include the resonance frequency; didn't help. Actually, since the variation around resonance frequency is large, it's better not to go above that and cut the data before it; still didn't help....
 

fitting s parameter to lumped model

My .snp file already has the DC (zero frequency) data.
 

cadence spectre nport

Using rational fitting with no DC point in the s-parameter file works.
 

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