Radiation Boundary and ground problem in HFSS 9.0

I have designed a microstrip antenna in HFSS 9.0. initially I defined radiation boundary every plane without z=0 plane. I know that if I don't define radiation boundary, this plane becomes PEC. Than this design worked but resonance frequency shifted. Normally, I have resonance at 307 MHz, but in yhe simulasyon I have 284 MHz.
On the other hand, I extended air box and I define every plane of this box radiation boundary. Then I define bottom plane of the substrate and side of the coax as a PEC. But I didn't obtaine any similar results.
My question is how can I convert my initial design to second one. I want to define radiation boundary on the every plane. But I didn't achieve to work. Please help me.

I put my design here. Please look at it. if you inform me, I am very gratefull.

Sincerely,
aermeydan

Hi, aermeydan,

I'm a HFSS beginner user. I've had some troubles with boundaries condition and excitations. In your example (I downloaded it) what kind of boundary and excitations you used? Did you use an unique port?

All the best,

LuizJr

PS: I so sorry my poor English, but I'm a Brazilian.