How To Calculate Impedance Looking Into A Device Port - Agilent Technologies N4413A User Manual

Using the Multiport Test System

How to Calculate Impedance Looking into a Device Port

How to Calculate Impedance Looking into a Device Port
The user-defined display can be used to convert reflection parameters to impedance. Consider
a device with one single-ended port and one balanced port.
In general, the equation is in the form:
Z = Z
R
where Z is a reference impedance and S is a reflection parameter.
R
For determining S, it is necessary to know the port and mode of interest. For this device, the
following table summarizes the correct variable for S.
Port Mode
1 N/A
2 Differential
2 Common
For determining Z , it is helpful to think of the device as having "terminals" rather than
R
"ports."
68
1 ( S )
+
×
----------------- -
( )
1 S –
S
S11
SDD22
SCC22
Chapter 3