What is the 3D radiation pattern of this chip antenna?
Your quest is certainly in the advanced antenna simulation space.
Mention of NEC based simulation could provide a solution, however given the chip sized antenna  the numeric precision of NEC would probably mislead.
I use an EM simulator called HOBBIES, where it is straightforward (but time consuming) to model your concept design in 3D, and get incredibly accurate simulations.. it happily runs on laptops thru to supercomputers..
The alternative is to simply probe the response of a working antenna, cognizant of near field issues.. again, not a simple task if you desire accuracy.