about HFSS simulation result!!

I simulate a 2-port transition,but there is something wrong with S21 of that modal:
I set 8 passes , the first pass and the secord pass:S21 is large,about -10dvB.
when the third pass overd,the value of S21 is -1.3dB,which is good for transition.
but from the pass 4 to pass 8. the S21 became larger and larger .from -2.6dB to -7dB I can not understand.why? according to theory.more the pass .better the result of simulation.
who can give me a explanation?thank you !

hi
dont worry
it has often happened for me
increase number of passes
keep Δs
change the dimensions of your model

if the problem persisted tell me exactly what your model is?

I just can not understand that when the pass number increased,why the result of S21 bacame worse than before.
why?

Hi,
When the number of passes increase it doesnt meen that the solution is going to be converged, sometimes it goes to the opposite way.
you may adapt hamidmoghaddas suggest,increase the number of passes.

dont warry about the convergence process, look just for the converged (last adaptive) final results.

ya they r right
it also happens with me
i do simulation first with 3 passes n tune my design after finalization i increase the number of passes for result convergence
n sometimes results improve n sometimes not
but dont get worse
n practical results r close to the results n sometimes better
so dont worry
see the convergence n after that modify ur design once agin
best of luck