About Duplexer simulation in designer.

I have made a Duplexer simulation in designer .I simulated Rx filter and Tx filter seperately frist.Then I combine them with Ant port ,I find the return loss is bad .I do not know how to tun it to better ,anybody can help me ?the attachment is my simulation picture.3ku.

It is very well in the simulation with single filter in HFSS,I didn`t obtain the curve never, I means it must need the best preformance for computers.
i am regard if you have attach the HFSS files.thks!

about your diplexers simulation,i think it`s important with the tap length in the single fiters,in the RX filers,you can use a quarter length at the TX f0,and wire the circuits to try it.

My simulation is made in ANSOFT DESIGNER with circle .not is a HFSS simulation.You know my means ?

I see!
how is the circuit model? i usually use to simulate models in ADS very easily,not designer.

do you have QQ.I will show you

you cannot just combine two filters as one Duplexer

When you design a filter, there is an assumed fixed, broadband output impedance. In a Duplexer, the two output ports both see the fixed, broadband output impedance in parallel with the output impedance of the other port. This means that you will have to tweak the both filters to match the new output load that it has.