+ Post New Thread

Results 1 to 7 of 7

- 16th February 2009, 14:55 #1

- Join Date
- Sep 2008
- Location
- Viet Nam
- Posts
- 7
- Helped
- 0 / 0
- Points
- 865
- Level
- 6

## 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

- Join Date
- Dec 2004
- Location
- New England, USA
- Posts
- 4,446
- Helped
- 1244 / 1244
- Points
- 31,775
- Level
- 43

## 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

- Join Date
- Aug 2008
- Location
- Hyderabad, Andhra Pradesh, India
- Posts
- 1,256
- Helped
- 253 / 253
- Points
- 10,953
- Level
- 25

## 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

- Join Date
- Sep 2008
- Location
- Viet Nam
- Posts
- 7
- Helped
- 0 / 0
- Points
- 865
- Level
- 6

## 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

- Join Date
- Dec 2004
- Location
- New England, USA
- Posts
- 4,446
- Helped
- 1244 / 1244
- Points
- 31,775
- Level
- 43

## 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

- Join Date
- Feb 2002
- Posts
- 749
- Helped
- 101 / 101
- Points
- 13,776
- Level
- 28

## s11 conversion to impedance

See below:

- 23rd February 2009, 04:21 #7

- Join Date
- Sep 2008
- Location
- Viet Nam
- Posts
- 7
- Helped
- 0 / 0
- Points
- 865
- Level
- 6

## s11 to complex impedance

thanks alot

+ Post New Thread

Please login