i am trying to examine the functionality of the system simulation for phase shifter.
i created a simple structure as shown in fig1. and fig2.

Just 2 simple TL sections with an ideal phase shifter connecting them. i have two similar structures one with 0 phase shifter and the second with 90 phase shifter (for comparisons).
i repeated the experiment 2 times, one time inserting the phase shifter between the two pins of a series face differential port and the second time i insert the phase shifter between two single pins discrete ports.
in both cases, i got unexpected difference in insertion loss magnitude between the two arms and I did not get 90 deg phase shift between the 2 arms.
the S parameter of the ideal phase shifters used are shown for your reference.
I appreciate if someone can help interpreting this unexpected results.

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