Bluetooth Antenna design parameters + selection

Hi all,

I am new to bluetooth design. Currently I have selected the BT chip.
I would like to know what kind of BT antenna (SMT type) should I choose?
What are the parameters should I take care of? I know the size of the antenna should be confined around 5 x 2.5 x 5.5mm. cost is not an issue yet, just thinking of performance at the moment.
I am thinking to measure the S11, efficiency, gain and maybe the radiation pattern.
I need some advise what I should beware of. Any advise & thoughts?

thanks

Use of inverted L-shaped antenna,
you can use HFSS simulation

Thanks mrgong.
Is there any website I can read on about inverted L antenna? I'm new to all this. What is the theory and how about the ground plane?

thanks,

Added after 3 hours 55 minutes:

about the component antenna, does it act as a monopole antenna? usually, the requirement is that the mounting area for the antenna does not have any ground plane. How does the counterpoise work?

Any advise ? thanks