I have a RF switching unit that multiplexes 4 input RF ports to 12 output
ports. The unit carries RF of a frequency range from DC to 1 GHz. It carries
GPS signals and other RF from an antenna.

Can you advise me of the design of a test jig to accurately test this unit?
The test jig will contain a Network Analyser.

Where I have a split path or differential measurement, do I always have to
use phase matched and batch matched cables?

Does my test jig switch calibration loads between ports? The cal load being
an open, a short and a load.

Do I get the paths the same by using phase matched & batch matched cables,
and then do a vector gen to save a 'footprint' of the test jig when it is in
a known good
state?

How do I minimise errors introduced by imperfections in the test jig? I am
looking for the test jig to measure the absolute SWR and insertion loss of
the RF switching unit, using S parameters.