How to measure a mixer group delay ripple with vector network analyzer?

Can anyone tell how to measure a mixer group delay ripple with vector network analyzer? I need to make a vector measurement plain scalar measurement is not enough

thanks in advance.

Mixer Conversion-Loss and Group-Delay Measurement Techniques and Comparisons. Agilent Application Note 1408-2:

http://www.home.agilent.com/agilent/...LENT_EDITORIAL