Polarizer axial ratio

Hi. I'm trying to design a Ka band Tapered corrugated polarizer. I somewhat was able to keep phase difference stable but the S parameters differ alot. What i was trying to ask when I search the papers they only use the phase difference between the ports for axial ratio calculation but not the amplitude difference. Shouldn't the amplitude difference be near 0 aswell for a true circular polarization. Like this it is an RHEP LHEP not RHCP and LHCP?

I solved it. I was comparing first mode and second mode for phase angle which ofcourse gives 90 degree difference all times.If you are holding the polarizer 45 degree angled.