Fresnel Zone Calculator

Augustin-Jean Fresnel\'s 1818 theory of wave optics introduced the concept of "Fresnel zones" as concentric regions where wavelets arrive in alternating phase. The theory originally explained light diffraction around apertures; a century later, radio engineers discovered the same geometry governed microwave propagation past obstacles.

Fresnel zones became critical design constraints for AT&T\'s 1950s transcontinental microwave-relay network. Each 30-mile hop needed 60% 1st-zone clearance to hit the design signal-to-noise targets. Surveyors traced paths on topo maps, identifying hilltops and valleys where obstructions would eat into the signal budget. The technique remained standard into the cellular-backhaul era of the 1990s.

Modern point-to-point gigabit links (up to 80 GHz E-band) make Fresnel clearance more forgiving because wavelength is millimeters instead of centimeters. But urban NLOS has become the dominant design challenge: 5G millimeter-wave links must operate in Fresnel-obstructed environments with heavy reliance on beamforming and multipath reflection.

Enter frequency, total link distance, and the distance from TX to your specific obstruction point (0 = compute at midpoint where zone is largest). The tool returns the 1st Fresnel zone radius, the 60% clearance threshold, and the 2nd zone radius.

For full path planning, also account for earth bulge on long links (>10 km): each km adds a fraction of a meter of curvature that effectively raises the radio horizon. Use the earth-bulge addendum in the formulas section. Everything runs client-side.