Per your request, I have sent to your email address the only thing we can provide for the BCM2073XS SIP module as nothing else exist related to antenna performance/characteristics.
Note the following:
There is nobody internally that can support questions related to this data (this includes on the forum)
The customer must have an NDA in place before you share it with them (your corporate NDA with us covers you)
If your inquiry is related to the BCM20736E, which does not include an internal antenna, then the customer would need to ask the Antenna Manufacture for this data.