SP simulation phase wrap

Hi,

I'm tring to do a SP analysis based on my measured touchstone file to see the phase difference between S31 and S21, which is supposed to be around 180 degree.

However, the result is like -179 degree at 50GHz while 179 degree at 51GHz. The phase is plotted between (-180,180].

I tried the unwrapp function but it doesn't help.

I wonder whether there is a function like phasewrap so that it can be transformed in to (0, 360].

I'm using virtuoso 6.1.8 and Spectre 19.1.0.373.isr7.

Any suggestions are welcome.

Thanks,

Yang