Where f represents wireless beam frequency. Now, if we use the wavelength formula, we get: R = √(λ * d 1 * d 2/ (d 1 + d 2)), accordingly to the picture:Īnd for the 1st Fresnel zone longest radius we have: In particular, if we want to determine the radius at any point in the first Fresnel zone, we would use the following formula: That is, when we have d 1 = d 2 = D / 2, and the above formula simplifies to:Īnd that's how we calculate the Fresnel zone! As you can see, it's not at all hard! To avoid any doubts, let's discuss the formulas for 1st Fresnel zone. If we want to get the longest Fresnel zone radius ( r nmax), we have to recall that an ellipsoide is the biggest at its center. λ is the wavelength of the wireless beam transmitted by the antenna and.

The formula for the radius of the n-th Fresnel zone reads: Here you can try our outstanding Fresnel Zone calculator to get an idea about the 1st zone radius and its 60% limit.Īs we now understand what Fresnel zones are, let's discuss how to calculate them – in the next section we give the math formulas for Fresnel zones. Subsequent Fresnel zones such as the 2nd and 3rd are also relevant but not as much as the first one. To avoid the harmful effects of indirect beams, we require to keep at least 60% of the 1st Fresnel zone free of obstructions. Whenever the phase angle shifts by one-half wavelength, you get destructive interference, meaning the signals get canceled. Such indirect beams travel through a longer path, meaning they get their phase angle shifted compared to the direct beam. Some waves will arrive directly at the receiver – the direct beam – and others will come after reflection with other surfaces – we call them indirect beams. Wireless antennas send waves in different directions.

However, even obstructions that do not cross the line of sight path can cause signal loss. Keeping it free when having constructions in the region between the antennas is critical because it can cause signal loss. In the Fresnel zone, the longest axis of the ellipsoid is the line of sight path.

It is called Fresnel Zone and looks like this: This region is determined by the distance between the antennas and the frequency of the wireless wave.

In wireless communication, we have a 3D elliptical region between the transmitter antenna and the receiver antenna.

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