I am designing a 2:2 stacked transformer to use as a balun in HFSS.
I have used 4 ports to simulate this but when I see the phase difference of the S parameters of the balanced ports from one of the balanced port, the difference is not 180 degrees. (S21-S31 is not 180). Since I am designing it for the first time I have no idea how to debug this. Any suggestions are appreciated.