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Modeling >> Transmission Lines and Other Distributed Devices >> S-param accuracy issue during Spectre transient simulation of low coupling induc
https://designers-guide.org/forum/YaBB.pl?num=1596557306

Message started by Aman101 on Aug 4^th, 2020, 9:08am

Title: S-param accuracy issue during Spectre transient simulation of low coupling induc
Post by Aman101 on Aug 4^th, 2020, 9:08am

Hi,
I am simulating a 4 port S-param file of two inductors with weak coupling between them (about -110dB).
First inductor: ports 1-2
Second inductor: ports 3-4
Nport settings: interp=linear, imptrunc=1.0e-6
Frequency: 0 : 100MHz : 300GHz

Simulation is comprised of a voltage source across port 1-2 while measuring voltage across ports 3-4.
Simulation is performed in AC and Transient (setting a pure 1V sinusoidal signal at 14.5GHz).

AC response is very smooth without any strange unexpected artifacts.
Tran response is converged without any blow-up artifacts.
Unfortunately, Tran response is 4 times the AC @ 14.5GHz!!!

I suspect it is originated from Spectre Impulse Response calculation.

Therefore I set the following Nport settings:
imptrunc=1.0e-12
imptrunc=0
datatrunc=0

All did not alter the results much.

When using S-param of stronger coupling between the inductors (-80dB), Tran and AC are identical!
using bbspice only makes things worse...

What are the Spectre settings for most accurate Impulse response?

Thank You.

p.s. I have read the article "7 Habits of Highly Successful S-Parameters" from 2019.

Title: Re: S-param accuracy issue during Spectre transient simulation of low coupling induc
Post by Andrew Beckett on Aug 9^th, 2020, 7:18am

I would suggest contacting Cadence's customer support.

Andrew.