Most antennas are “beam concentrators” - the traditional TV antenna is an example. But since RF signals weaken as the square of the distance (inverse square law) the only practical way to concentrate the power that is radiated is at the antenna. A parabolic dish for example, can increase the strength of a microwave signal many thousands of times but there is no free lunch, it does so at the cost of directionality. So you could create a 5G site with a very strong signal, but only as a narrow beam in one direction.
Thank You. I didn’t want to push my luck and post my question again on the new thread.