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Measurements >> RF Measurements >> Smith Chart - S-Parameters Plot
https://designers-guide.org/forum/YaBB.pl?num=1312007575

Message started by avins on Jul 29^th, 2011, 11:32pm

Title: Smith Chart - S-Parameters Plot
Post by avins on Jul 29^th, 2011, 11:32pm

Hello,

My basic question is with regards to smith charts.

Please look into the link and clarify my doubts regarding plotting of S-Parameters for different frequencies on smith charts. I have prepared a word document and attached it.

The link is

http://twl.sh/p6qn4L

Thanks,
engineer

Title: Re: Smith Chart - S-Parameters Plot
Post by RFICDUDE on Aug 3^rd, 2011, 6:11pm

I am fairly sure no one will click the link, so perhaps you should upload a picture or describe the problem instead if you really would like someone to look at the problem.

Title: Re: Smith Chart - S-Parameters Plot
Post by avins on Aug 3^rd, 2011, 11:14pm

Hello,

I have attached the word document for reference.

Cheers,
avs

Title: Re: Smith Chart - S-Parameters Plot
Post by aaron_do on Aug 4^th, 2011, 7:04am

Hi avins,

I'm not trying to be mean, so don't take this the wrong way, but I think you are missing the point. Firstly, we don't really know where that link is going to lead us, just like we don't know what's contained in that .rar file. But even if it was perfectly safe, its much more convenient for people to read and answer questions directly on this forum.

best regards,
Aaron

Title: Re: Smith Chart - S-Parameters Plot
Post by avins on Aug 4^th, 2011, 10:16am

Okay, I have attached the pdf. I hope I get the solution.

Title: Re: Smith Chart - S-Parameters Plot
Post by rfcooltools.com on Sep 30^th, 2011, 1:43pm

avins,

The Smith Chart is just a visualization tool where one can look at the magnitude and phase simultaneously of a complex reflection response. It can be used to intuitively determine what matching elements might be needed and how to get there.
The plotting coordinate system is simply a Polar plot of Complex numbers In this case Re(SNN)+IM(SNN). With an overlay of grid lines that map it more meaningful parameters such as Q and Impedance and admittance etc. In your tool the program is converting the data represented at the marker to impedance ratio relative to Zo.

The smith chart can be viewed as follows

For an s-parameter file the information in the standard file is either dBmag and angle, magnitude and angle, or real or imaginary. All can be represented as Re(SNN)+IM(SNN). Disregard the grid lines for the time being and then you will be able to notice its just a polar plot of this signal. If that is clear then what are the gridlines for? They are a mapping of reflection to an impedance/admittance Ratio relative to Zo.

When I first saw the Smith chart my reaction was what do I do with this, but after using it for a while it is a tool that would be hard to do without. To learn it you might want to only view a single frequency and then observe how the smithchart behaves when you add or remove components.

http://rfcooltools.com