Low key fob lock/unlock distance

Model: e90 LCI ( 2011 ) As the title states, the distance of locking/unlocking with key fob is very low. I remember the days when i could unlock it from 20m, but now i have to stand max 1m from the car.

Does anyone know if changing the diversity antenna resolves the issue? And do i need to do some coding if i decide to change it?