balun simulation ads

I have simulated a coaxial balun which will transform 50ohm unbalanced impedance to 25ohm balanced impedance as the following circuit:

The following picture is the simulation result, I get 100ohm impedance of port2 and port3.

How can I get the correct result?

Change port 2 and 3 to 25 ohm differentially. Or use configurations for impedance transformation.

Sorry,but how to change impedance differentially?

click on 50 and type the new one

Changing port 2 and 3 inpedance to 25 ohm achieves impedance matching for the differential case. But if you measure the input impedance, as you did, you will still get a wrong result (75 ohm instead of 100 ohm before). This is because you are actually measuring port 2 and 3 input impedance for the single ended case, which can't be matched.

Yes,I get 75ohm when changing port2 and port3 to 25ohms.Is there any method I can simulate balanced impedance in ADS?

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