How to Get 3-port S-parameters From a 2-port VNA Measurement
S-parameters are fundamental quantities in signal integrity, and an ability to understand them from measurement or analysis is very important. If you have a 3-port network, like a power divider or circulator, it may appear that you must use a 3-port VNA to measure these S-parameters. It is always acceptable to measure between two ports, but you need to know what exactly it is you are measuring.
As it turns out, you can use a 2-port VNA...