drawing a sinus structure having 3mm period

hello;

I would like to draw antennas having sinus structure. this sinus structures' s period are 3mm, 5mm respectivelly... I can draw the sinus antenna having 5mm period. In spite of that, I can not draw the sinus antenna having 3mm period. Pictures is following below;

3mm

5mm

It can be understanble from pictures that 5mm does not have any problem, in spite of it, 3mm has a serious problem.... moreover when I want to make a simulation of 3mm sinus antenna, hfss produces error which is a mesh error during the simulation...

what can I do againist this kind of problem.... becasue I encountered a problem ismilar to this before...

I will be waiting for your response...

thank you very much....

be welll.......