My problem is that I'm not sure how to perform the "matrix renormalization" step on page 10 of the NPL document. What calculations are required to convert the six raw VNA measurements (for example, the transmission measurement between ports 1 and 3 of the DUT), and the measured (complex) reflection parameters of the loads attached to the DUT ports, into the normalized 4 x 4 matrix?
I've found the code I need on the scikit-rf site - specifically,
renormalize_s (and associated functions) from http://scikit-rf.readthedocs.io/en/latest/_modules/skrf/network.html . This is Python code that uses numpy for the calculations.
For anyone else interested, this page describes how to perform the measurement using scikit-rf.