What are Antennas
|Examples of increasing antenna gain. Top: Low gain dipole. Middle: High gain dipole. Bottom: High gain directional.|
- Just as antenna designers cannot build a perfect sphere, they cannot build a perfect cone. As a result, there is some amount of RF energy that is projected and received in the other directions. These are known as backlobes and sidelobes, as seen in the figure above. If two neighboring antennas are placed very close together, they can interfere with each other, thus a certain amount of separation distance (at least a few feet) is generally recommended when placing directional antennas next to each other.
- The beamwidth is defined by where the energy of the antenna drops by 3 dBi (i.e. half) of the peak. Thus, while the gain of the antenna is less beyond this beamwidth, it is also generally not zero, which needs to be accounted for in Wi-Fi design.
|Examples of different antenna types, with their typical potential for beamwidth and gain.|