How to setup the airbox for simulating RFID antenna at 13.65 MHz in HFSS?

Hi, everybody

I'd like to simulate RFID Antenna at 13.65 MHz by HFSS. How do I setup my airbox? If I still follow the rule that the height of airbox is approximately quater-wavelength, it is huge. Do you have any suggestions? Thank you!

For 13.56 MHz coil, It is usually not used for far field. So for your simulation, you dont need to have a large air box, This is my opinion. Hope anyone can comment on this.