interval modification in cst simulation

i've successfully simulate the antenna in frequency range of 0-12 without any warning and error. but as i want to simulate the antenna in 0-20, it couldn't successfully simulate. it has error. what actually goes wrong in my antenna? how to modify the interval of the graph ?

Can you write which error have you it? What type warning is it?

"some higher propagating modes at port 1 are not considered in time domain calculation. this possibly leads to inaccurate energy balance. consider to increase the number of modes or decrease the upper frequency limit."

this error occur when i set the freq range 0-15. but, when i set the freq 0-14,there's no error.
anyway, for vivaldi antenna,it use waveguide port isn't it?

Yes, it is typical. You have vivaldi antenna and the end is very similar as waveguide horn antenna. Do you know something about waveguide mode? Your structure is too large (for > 14 GHz) and is it possible, that in your structure is next waveguide mode. That mean it is better set in properties of port "Number of mode" to 2.

actually i have no idea about waveguide mode. i am a beginner user for cst simulation. do u mean that i just simply need to right click at port part and increase the number of mode to 2? "the exist hybrid modes at inhomogenous port 1. this could lead to an inaccurate energy balance. please check your structure">>> i got this error after increase the number of mode.

right now i have done my vivaldi antenna design but still cant get the UWB graph.

---------- Post added at 13:28 ---------- Previous post was at 12:26 ----------

is it possible if i assign full plane waveguide port for my vivaldi?

Yes, waveguide port is OK..... exactly with small mistake.... try study the attachment.

If you want, you can send me your project.

I will be there on Monday.

eventually,can solve the problem.tq :)

Could you explain, how did you solve that problem about a simulation errors?

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