# Fresnel Zone Calculator

Radio frequency line of sight is defined by Fresnel Zones which are ellipse shaped areas between any two radio antennas. This calculator calculates the radius of the Fresnel Zone at its widest point. The distance between the two radio antennas and the frequency of operation are required to compute the radius of the Fresnel Zone.

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m  What is Fresnel Zone?

In a communication system, the Fresnel zone is the long ellipsoidal-shaped area/region in space around the line of sight (LoS) between a transmitter and receiver antenna.

It is the confocal prolate ellipsoidal shaped area/region in space around the central line of the direct transmission path line (i.e., line of sight (LoS) between a transmitter and receiver antenna. In other words, the Fresnel zone is a long ellipsoidal-shaped region around the LoS.

The Fresnel zone consists of multiple zones (1,2, 3,…, n) with zone 1 having a strong signal than the next zones 2,3,…, n. During the design of microwave parabolic antenna systems (is a highly directive system),  the calculation of Fresnel zone size (i.e., radius) helps the antenna installer to decide if an obstacle, such as a tree/building, is going to make a significant impact on signal strength. If any obstacle/object is found, the antenna installer will elevate antennas to clear the obstruction.

The Fresnel zone size (i.e., radius) depends on the distance between the transmitter, receiver, and operating frequency.

Based on the below fig, the formula for calculating the radius of each Fresnel Zone (1,2,3,.., n) is:  Where,

R = Radius of the Fresnel Zone in m/ft

n = Fresnel Zone number (>0)

λ = c/f = wavelength

To maximize signal strength between the transmitter and receiver, the antenna installer needs to keep the obstruction-free direct transmission path (i.e., line of sight) line and also the area around it (i.e., Fresnel Zone). The thumb rule tells us that the primary Fresnel zone (i.e., n=1) would ideally be 80% clear of obstacles, but in real life it must be at least 60% clear.

Hence, the calculation of the size (radius) of the 1st, or primary Fresnel zone is important for a given antenna system, and this calculation will enable the antenna installer to decide if an obstacle will make a significant impact on signal strength.

The Fresnel zone calculator helps to calculate the size of the first Fresnel Zone.