hfss rcs airbox

Hello guys,
I have big problem with simulation accuracy of HFSS. I simulate an electrical small antenna(meander line antenne) with radiation boundary of a airbox. The results depend too much on dimension of the the airbox, although the mesh is fine and the convergence is also okay. The HFSS-modell has been attached, run the parameter sweep you will see the different results.

Has anyone the similary problem with HFSS? or any HFSS professional knows the reason. Tips and advices are appreciated!

Hi , my friends
I've used many EM softwares for antenna design and in most of them the simulation accuracy depends the antenna airbox untill a specific dimension that's a little different in any software .
But if your simulation results alwyse change with antenna airbox's dimension , I think you should have errors in modeling. because the shape of antenna airbox should be based on your antenna pattern.
Anywhere, for HFSS the airbox should be away from antenna surface approximately .5-2 times wavelenght (far field) . and for microstrip antenna it also should be away approximately 5-10 times substrat's hight.

I hope it'll be helpful .

best regards : ali110

I haven't looked into the project. However, try to use the infinite ground plane and at least 1/4 lambda (of lowest freq) distance from the structure an the airbox.

wlcsp

Did you try using PML? It helps.

hi

i try to measure the RCS of a simple object(flat plane 4x4 cm ) but it depends a lot(5-6 dBsm) from the dimension and position of the airbox, it is possible?

hello,

as far as I know the airbox only absorbs electromagnetic energy of fields arriving perpendicular with respect of the wall of the airbox. PML absorbs electromagnetic energy coming from any direction. therefore, use airbox for preliminary results where accuracy is not yet vital and switch to PML when acuracy, especially in radiation pattern, becomes more important.

best regards

I found a paper about problem.

i've not enough points to download it

can you send it to me by email?

puccini.gemma at inwind.it


thanks
Meini

i think the feed has not been setup correctly. you need a cap. look for some examples from ansoft or in this forum.

Hi

I had the same problem for the simulation of slot antennas.
I solved it by assigning mesh refinement (inside and surface) in the sensitive places, and using pml. cause pml doesn't need to be as far as λ/4 , and therefor we can use much more mesh refinement, with less memory problems.

hope this helps

sara

walls of the air box is to absorb the electromagnectic field radiated from the antenna so if u r concerned about the radiation pattern then keep the walls of the box atleast 10 times of the wavelength away from the antenna design