plotting S-parameters as a function of port phase

Hi,

My system is a microwave chip with 4 ports.

I was wondering wether it is be possible to plot S paramteters as a function of the port phase, and not as a function of frequency. Basically I have two ports that are ON (1 and 2), that have a phase difference \theta between them that I need to vary. I also have two ports that are OFF (3 and 4) for the outgoing signal. I need to get S13 and S14 as a function of \theta.

If this is possible, can sombody indicate to me a way to do that?

Thanks in advance, Nicolas