Fresnel Zone Calculator

The Fresnel zone is an ellipsoid-shaped volume around the direct path between transmitter and receiver. It represents the space in which radio waves propagate significantly. Any obstacle within this zone can cause diffraction losses. The first Fresnel zone is the most critical: it is recommended that at least 60% of its radius be clear of obstacles for a link without significant loss.

The approximate formula for the first Fresnel zone at the obstacle point is: r (m) = 17.32 x sqrt((d1 x d2) / (d x f_GHz)), where d1 and d2 are the distances in km from the obstacle to each endpoint, d is the total distance in km, and f is the frequency in GHz. At the midpoint of a 1 km link at 5 GHz: r = 17.32 x sqrt(0.25 / (1 x 5)) = 17.32 x 0.2236 = 3.87 m.

100% clearance is theoretically optimal but nearly impossible to achieve in practice. ITU-R P.530 studies show that maintaining 60% of the first Fresnel zone clear of obstacles results in less than 6 dB of loss compared to free space. This is the practical compromise used to design point-to-point links (microwave backhaul, radio relays).

Partially. For point-to-point links (backhaul between BTS, rural links), the Fresnel zone is an essential design criterion. For urban cellular mobile networks, the model is less applicable because propagation is dominated by multipath, reflection, and diffraction from buildings. Empirical models (Okumura-Hata, 3GPP 38.901) are used instead.