Friis transmission equation

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The Friis transmission formula is used in telecommunications engineering, equating the power at the terminals of a receive antenna as the product of power density of the incident wave and the effective aperture of the receiving antenna under idealized conditions given another antenna some distance away transmitting a known amount of power.^[1] The formula was presented first by Danish-American radio engineer Harald T. Friis in 1946.^[2] The formula is sometimes referenced as the Friis transmission equation.