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Pi Network & S - parameters

Hi,

I am new in the RF field and I have a question regarding Pi Networks and S parameters.

I was recently reading an article about Pi networks and it uses in RF. I am confused about a couple of things. The article said the k=1/S21, where k is the attenuation constant. How do you derive this relation between k and S21. I know that k=10^(A/20), where A is the value of attenuation, does it have something to do with this?

My second question is, the article says that the load reflection coefficient gammaL=1/k^2. How do I derive this?

Thanks, Nam

Reply to
genenamg
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I read in sci.electronics.design that snipped-for-privacy@yahoo.com wrote (in ) about 'Pi Network & S - parameters', on Thu, 16 Dec 2004:

No, that equation converts between A in decibels and k as a pure number.

S21 is the forward 'gain' (a number less than 1 for a passive network), so the attenuation coefficient is obviously its reciprocal.

You will find the answer on the pages up to page 17 of the document:

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Remember that in general s21 is a complex number (there is phase-shift through the network) and that s21 = 1/k.

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John Woodgate

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