
16th February 2009, 14:55 #1
Newbie level 4
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 Sparamter)
Please help me
Thanks

16th February 2009, 14:55

16th February 2009, 16:15 #2
Advanced Member level 5
s11 impedance
Z = (1 + ρ)/(1ρ)
ρ = (ZZ0)/(Z+Z0)
Z0 is usually 50 ohms. These calculations are, of course, complex.

16th February 2009, 16:15

18th February 2009, 13:17 #3
Advanced Member level 4

18th February 2009, 13:17

21st February 2009, 14:30 #4
Newbie level 4
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
Advanced Member level 5
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
Advanced Member level 3
s11 conversion to impedance

23rd February 2009, 04:21 #7
Newbie level 4