Error in the convergence of antenna in hfss

Hello,
i hae a prblem in my smulation for antenna monopole
when i run this prject this anayse is ok and run is about 2 hours and fnaly he dsplay me error in cnvergence
what is the solution please

The solution to your problem, like most problems in life, will depend on what the error is.

Do you get some results? Do the results looks reasonable?
How many adaptive passes does your simulation do?

in the first i dnt have result but when i m delete the groud i have obtain the result ( because i have a stucture diferent )
i have a question about the dimension of antenna monopole please
if the frequency = 2.4Ghz so the length of antena L=c/(2*f)
so the dimension of ground andd the cylinder of the port how can i caluculate them?



i have 15 pass

Firstly, the length of a monopole antenna should be a quarter wavelength (i.e. L=c/(4*f)). That's why, when you remove the ground-plane, you have better results as in that case it works as a dipole antenna at 2.4 GHz, with ground-plane the antenna is optimized for 1.2 GHz (you will see this resonance in your S-parameters).

Secondly, the dimension of the ground plane will alter your radiation pattern, it should at least be a few wavelengths in both dimensions to reduce this "skewing" of the pattern. Check with far-field simulations if the pattern is ok, otherwise increase the ground plane size as much as is feasible.