The Designer's Guide Community
Forum
Welcome, Guest. Please Login or Register. Please follow the Forum guidelines.
Dec 3rd, 2020, 12:37pm
Pages: 1
Send Topic Print
Curve fitting of center-tapped inductor (Read 4292 times)
neoflash
Community Fellow
*****
Offline

Mixed-Signal
Designer

Posts: 389

Curve fitting of center-tapped inductor
Mar 17th, 2008, 7:38am
 
Hi, folks:

I come up with a strange thing when doing curve fitting for a differential center-tapped inductor.

The original version of the inductor is a two-terminal differential inductor. I did curve fitting to find the equivalent circuit model. And the fitting seems good.

The next step I added a center-tap and got a 3-port s-parameter from field solver. The problem is when I'm doing the curve fitting again. the mutual inductance in the circuit model was forced to zero by the fitting tool. The fitting seems OK but not as good as two-port one. The inductance and Q is ok but the s-parameter related with the third port are not well fitted.

Any one ever experience same thing before? Any suggestions?

Regards,
Neoflash
attached is the equivalent circuit model for curve fitting. Parameters are found by fitting tool.
Back to top
 

3tind.JPG
View Profile   IP Logged
neoflash
Community Fellow
*****
Offline

Mixed-Signal
Designer

Posts: 389

Re: Curve fitting of center-tapped inductor
Reply #1 - Mar 18th, 2008, 5:52am
 
The most strange thing is that the mutual coupling between inductors are forced to be zero by fitting tool, I can't understand.
Back to top
 
 
View Profile   IP Logged
pancho_hideboo
Senior Fellow
******
Offline



Posts: 1424
Real Homeless
Re: Curve fitting of center-tapped inductor
Reply #2 - Mar 18th, 2008, 9:53pm
 
How is port-3 treated in your fitting tool ?
Isn't Port-3 treated as ground ?
Back to top
 
 
View Profile WWW Top+Secret Top+Secret   IP Logged
neoflash
Community Fellow
*****
Offline

Mixed-Signal
Designer

Posts: 389

Re: Curve fitting of center-tapped inductor
Reply #3 - Mar 19th, 2008, 5:41am
 
neoflash wrote on Mar 18th, 2008, 5:52am:
The most strange thing is that the mutual coupling between inductors are forced to be zero by fitting tool, I can't understand.


No. It is not treated as ground. Since this port will connect to a current source in circuit design. Top-biasing of current will be used.
Back to top
 
 
View Profile   IP Logged
pancho_hideboo
Senior Fellow
******
Offline



Posts: 1424
Real Homeless
Re: Curve fitting of center-tapped inductor
Reply #4 - Mar 19th, 2008, 6:58am
 
If port 1 and port2 are drived with symmetrical odd mode,  where only differential(odd) mode is characterized,
port 3 is virtual ground.
And even if you are not driving port 1 and port2 with symmetrical odd mode, manupulation of S-parameter for differential characterization results in port 3 as virtual ground.

Or you are doing full 9 parameters S parameter fitting without invoking odd and even mode concept ?  
Back to top
 
 
View Profile WWW Top+Secret Top+Secret   IP Logged
neoflash
Community Fellow
*****
Offline

Mixed-Signal
Designer

Posts: 389

Re: Curve fitting of center-tapped inductor
Reply #5 - Mar 19th, 2008, 7:04am
 
pancho_hideboo wrote on Mar 19th, 2008, 6:58am:
If port 1 and port2 are drived with symmetrical odd mode,  where only differential(odd) mode is characterized,
port 3 is virtual ground.

Or you are doing full 9 parameters S parameter fitting without invoking odd and even mode concept ?  


I'm treating the 3-port network as a full 9 parameters network.
Back to top
 
 
View Profile   IP Logged
email_gz
Junior Member
**
Offline



Posts: 31
gaoz.mail@gmail.com
Re: Curve fitting of center-tapped inductor
Reply #6 - Mar 27th, 2008, 9:43pm
 
Physically,differential inductor is just a special 3 port transform (T coil) and this sharing port have no ac current pass through. so when you connect this port  to a current source , so Iac*S*(-M)=0,then just can be seen as two inductor L+M,L+M series conneted.
Back to top
 
 
View Profile email_gz email_gz   IP Logged
Pages: 1
Send Topic Print
Copyright 2002-2020 Designer’s Guide Consulting, Inc. Designer’s Guide® is a registered trademark of Designer’s Guide Consulting, Inc. All rights reserved. Send comments or questions to editor@designers-guide.org. Consider submitting a paper or model.