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- 16th February 2009, 14:55 #1

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## converting s11 to impedance

Dear all.

I'm a new comer, i wish to learn alot from you.

I have designed a PA module using BLF278. but datasheet only give me S11,S12.S21.S22 and I need convert to Zin and Zout in complex impedance. (or how to use S-paramter)

Please help me

Thanks

- 16th February 2009, 14:55

- 16th February 2009, 16:15 #2

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## s11 impedance

Z = (1 + ρ)/(1-ρ)

ρ = (Z-Z0)/(Z+Z0)

Z0 is usually 50 ohms. These calculations are, of course, complex.

- 18th February 2009, 13:17 #3

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## s11 to impedance

You can use the calculations from the link

http://www.rfcafe.com/references/electrical/s-h-y-z.htm

1 members found this post helpful.

- 18th February 2009, 13:17

- 21st February 2009, 14:30 #4

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## convert s11 to impedance

Thanks you very much for so many helps.

But BLF278 only give me S11 and Φ; (see table). I must convert to Zs and Zl in complex impedance.

Thanks.

- 21st February 2009, 18:19 #5

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## s11 convert s22

Maybe I wasn't clear enough.

Zin = 50*(1 + S11)/(1 - S11)

And

Zout = 50*(1 + S22)/(1 - S22)

where Zin and Zout are the impedances looking INTO the device. You have to mutiply by 50 to convert the normalized impedance into ohms (assuming your S parameters were measured on a 50 ohm network analyzer).

The table you published has S11 as mag[s11] and ang[s11] for various frequencies. These are complex numbers. You do the complex division, one frequency at a time, and the answer is also a complex quantity, either in magnitude and angle, or Real and Imaginary parts, depending on how you choose to do the arithmetic.

Rich

www.MaguffinMicrowave.com

- 21st February 2009, 18:27 #6

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## s11 conversion to impedance

See below:

- 23rd February 2009, 04:21 #7

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## s11 to complex impedance

thanks alot

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