Izaz Ali Shah Ot will be great help if you could share detail procedure to upload .stp file in hfss as I am not able to find the procedure of import in HFSS and how can I integrate my antenna with that CAD file. Please help or share your whatsapp number so that I can get in contact.
It depends on the body part on which you are placing the antenna. If you are placing the antenna on the top (roof) of the vehicle body, then it (body) must be PEC.