Z11 is the complex input impedance of a two-port network that has an
open-circuit at the output port. That is, the output current is zero.

v1=Z11* i1 + Z12 * i2
v2=Z21* i1 + Z22 * i2

Z11= v1 / i1 when i2=0
Z22= v2 / i2 when i1=0
Z12= v1 / i2 when i1=0
Z21= v2 / i1 when i2=0

Z11 should be confused with S11, which is the reflection coefficient at the
input port.

S11=[(Z11-1)(Z22+1)-Z12*Z21]
/ [(Z11+1)(Z22+1)-Z12*Z21]

Bill W0IYH

wrote in message
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Joel Kolstad wrote:
wrote in message
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Etcetera. But i don't wanna do vector
math all the time. And i also don't wanna
graph this gamma on the Smith chart by hand.

So i was wondering if there was a program
out there, that will do this calculation
for you?

Not that I'm aware of, but it'd be trivial to code up in MatLab,
MathCAD, or
even Excel if you wanted to...

Heck, even 'Windows Scripting,' which is really Visual BASIC, would
work.
In the *NIX word, there's PERL, Rexx, etc...


Well, i've never used Excel for vector algebra.

Could you throw something together on Excel, and send
me the file, so i know what you mean? If you could,
include the bi-linear transformation:

As i understand the Z11 formula
i stated, you will still get a vector
solution, so in essence the Z11 will
be a gamma reflection coefficient, or magnitude
(from 0 to 1) with an angle. So on top of that, you
will need to convert this gamma to
the complex series equivalent impedance,
which you can do graphically on the Smith, or
by using:

Gamma(Z11) = (ZL-Zo) / (ZL+Zo)

And letting Zo=characteristic impedance (assume
real! Usually 50 ohms), and then solving for ZL.


Slick