RF link geometry analysis determines whether a wireless communication link between two antennas is feasible by calculating line-of-sight clearance, Fresnel zone obstruction, and field region boundaries. The first Fresnel zone radius at any point along the path is calculated as r = √(n × λ × d1 × d2 / (d1 + d2)), where λ is wavelength, d1 and d2 are distances to each antenna, and n is the zone number. At least 60% of the first Fresnel zone must be clear of obstructions for the link to operate without significant signal degradation. The far-field boundary (Fraunhofer distance) is 2D²/λ, where D is the antenna aperture — measurements and link calculations are only valid beyond this distance. Earth curvature must be accounted for on links longer than about 5 km, typically using a 4/3 effective Earth radius model to account for atmospheric refraction.
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