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Measurements >> RF Measurements >> Plot s11 on Smith chart
https://designers-guide.org/forum/YaBB.pl?num=1479605578

Message started by engrvip on Nov 19^th, 2016, 5:32pm

Title: Plot s11 on Smith chart
Post by engrvip on Nov 19^th, 2016, 5:32pm

Hi

When i say i am plotting s11 parameter on Smith chart, does it mean that s11 gets converted to z11 and hence plots normalised impedance value on SC.

Similarly what about s21 can it be plotted on SC since it is a gain parameter.

KINDLY clear my confusion.

Title: Re: Plot s11 on Smith chart
Post by tzg6sa on Jan 31^st, 2017, 2:18am

S11 is like a reflection coefficient. There is a bijective connection between reflection coefficient and normalized impedance. No conversion is needed on the smith chart - that's point of the chart! - just different scales are used.

S21 is a ratio of incident and reflect waves. The waves are merely on different ports, so in princip it is the same as S11. Nevertheless I do not see the point of using a Smith chart for S21. The middle point of the Smith chart has no meaning here, no matching is required in this parameter. If you have S21=10+j0, then where would you add it on the Smith chart? A conventional magnitude plot says more about S21.