In point to point wireless communications, it is important for the line of sight between two wireless systems to be free from any obstruction (terrain, vegetation, buildings, wind farms and a host of other obstructions). As any interference or obstruction in the LOS can result in a loss of signal.

While installing a wireless communication system, it is important to keep an elliptical region between the transmit antenna and the receive antenna free from any obstruction for the proper functioning of the system. This 3D elliptical region between the transmit antenna and the receive antenna is called the Fresnel Zone. The size of the ellipse is determined by the frequency of operation and the distance between the two sites.

The Fresnel zone is made up of multiple zones, with zone 1 having the strongest signal and following zones (Zone 2, and Zone 3) having weaker signals.

Based on the figure above, the Fresnel Zone is calculated using the following equation.

Click here to use the Fresnel Zone Calculator on everything RF.