Antenna Radiation Direction--Antenna Radiation Enhancement

Several symmetrical dipole antennas can form an antenna array to control the radiation direction. The "flat donut" radiation pattern suggests the energy is further converged on the horizontal direction.
A reflection panel also works for biasing the radiation to one side.
The following graph shows how the reflector works. By placing the reflector beside the antenna feeder, the radiating power are reflected to one side – thus increases the gain. 
The parabolic shape reflector works like a torch which converges the energy to one point, so that the gain dramatically increases at the pointing direction.