about impedance measure?

Hi , How to measure impedance for balance output by network analyzer ?
What is difference from the single output measure?
Best regards !

"Agilent Technologies Impedance Measurement Handbook"
it have details about impedance measurement.

http://bakelite.pd.infn.it:5210/Docs.../5950-3000.pdf

whit a common VNA do spar measuremen connecting DUT as "unbalanced" (terminating the other port into 50 Ohm Load).
You'll get a set of 2 spar datafiles.
Using Agilent AppCad 3, convert into 1 file of balanced spar.

I use Softplot V5.0 (http://www.softplot.com) with ZVRE from R&S.
You can transfer unballanced data results direkt into the software and calculate ballanced impedances.