Defining The Reference Impedance In User-Defined Equations - Agilent Technologies N4413A User Manual

Using the Multiport Test System
How to Use User-Defined Displays
This quadrature hybrid can be further characterized by employing other user-defined
calculations. For instance, you could characterize loss with the equation:
(S21+(-1)^0.5*S31)/2^0.5
which translates to:
1
------ - S21 (
+
2
You could also characterize cancellation with the equation:
(S21-(-1)^0.5*S31)/2^0.5
which translates to:
1
(
------ - S21
–
2
These are the mathematical equivalents of connecting an ideal 90° hybrid to the DUT in such
a way that the outputs either add constructively or cancel each other.

Defining the Reference Impedance in User-Defined Equations

When you define a user-defined parameter, the system does not know the correct reference
impedance for displaying impedance and conductance markers.
You can define your port impedance values by editing the impedanceDef.txt file. The default
location of this file is ..\Program Files\Agilent\system\, the actual location may be
different.
Instructions for editing impedance definitions are included in the file. Make sure you edit and
save the file in ASCII text only format.
The section title in the impedanceDef.txt file must match the variable name created in the
User Defined Display dialog box. Impedance equations defined here will only be loaded if the
data tag (the variable name) is in use.
NOTE Maintain a copy of your unmodified (original) impedanceDef.txt file in a safe
location.
66
j S31 )
j S31 )
Chapter 3