Help! AIR BOX size in HFSS ?

I can't find out the proper size of the air box in HFSS, cuz the result shows a quiet

big difference btw HFSS and sonnet. how to define the air box size?

i think the length more than wavelenght/4 doesn't work..it's troubling me to

define the air box in HFSS. Any expert can help? thx a lot !

And the file is attached in below.

hi
if simulating a planar structure, just the hight of air on substrate should be 10*h
(h: substrate thickness)
air box should completely contain all elements.
GOODLUCK

can you describe the difference between the Sonnet and HFSS with different size of air box?
if you calculate it as an inductor
I guess you result changes a little with different air box,and the inductane and Q of hfss is larger than Sonnet,right?

hi
I sure the airbox size have large effect on return loss but a little effect on radation pattern.

Does the airbox around the structure have to be defined as radiation boundary? Or, shall I just select the faces of the airbox and define them to be radiation boundaries? I'm currently simulating microstrip lines.

Your answers are here

http://www.emtalk.com/tut_1.htm