[SI-LIST] Re: length of transmission line in ADS for Z0 modeling

Rahul,
This is a bit of a hack, but if you don't care for lots of equations, you 
can set up an S-parameter analysis with the Z0 of the ports to be a tunable 
variable, you can sit there with a slider bar and tune the characteristic 
impedance of the system until S11 collapses to a minimum squiggle (ideally, 
a dot) at the center of a Smith Chart.  That is, when the Z0 of the 
"measurement system" equals the Z0 of your structure, the reflection goes 
away.  (actually, complex conjugate)

You may not have thought of using Tuning an analysis parameter like Z0, but 
it's simple and requires little thought or setup.

The main thing is to have a nice straight, simple, short piece of line where 
you get a clean S11.  (ie - this might not work for complex structure with a 
lot of TDR detail).  Once that works for one point, it is possible to 
automate swept-value optimizations in ADS, so you could potentially sweep a 
geometry value and plot this variable vs. your swept dimensions, or do 
countour plots, etc.

This quick & dirty tune method also works like a champ for differential 
structures and EM results, and could be adapted for Large Signal S11 and TDR 
as well.

Daren McClearnon
Agilent EEsof marketing


----- Original Message ----- 
From: "Rahul G" <skgupta2005@xxxxxxxxx>
To: <si-list@xxxxxxxxxxxxx>
Sent: Wednesday, November 12, 2008 2:20 AM
Subject: [SI-LIST] length of transmission line in ADS for Z0 modeling


> Hello All
> I want to model a microstrip/stripline in ADS to find characteristic
> impedance using s-parameter simulation. I dont want to use LineCalc...
> I am using multilayer models and give sweep of all parameters (dielectric
> constant, trace width, height, thickness etc..) and plot Z0 vs impact of
> each parameter..
> my problem is what should be length of transmission line in simulaiton? 
> do
> i need to keep it quarter-wave or any length will do..
> i just need to find mag(s11) and use formula (ZL-Z0)/(ZL+Z0). please 
> correct
> me, if I am wrong..
> Thanks
> Rahul..
>
>
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