Friis

Friis is a Scandinavian surname most commonly found in Denmark and Norway. It has been borne by individuals across fields such as science, engineering, government, and the arts, and its usage is reflected in various place names and institutions in the region.

In science and engineering, the name Friis is chiefly associated with the Friis transmission equation, a fundamental relation in radio communications. The equation describes the power received by an antenna from a transmitting antenna in free space. The standard form is Pr = Pt Gt Gr (λ/(4πR))^2, where Pr is received power, Pt is transmitted power, Gt and Gr are the antenna gains, λ is the wavelength, and R is the separation distance.

The equation is named after Harald Friis, a Danish electrical engineer, reflecting its origin in early work on link budgets for wireless transmission. Beyond this contribution, people with the Friis surname have been active in various domains in Denmark, Norway, and the broader Nordic region.