Friis Transmission equation (with dB units)
Description
The Friis transmission equation is used in telecommunications engineering, and gives the power received by one antenna under idealized conditions given another antenna some distance away transmitting a known amount of power. The formula was derived in 1945 by Danish-American radio engineer Harald T. Friis at Bell Labs.
If the gain has units of dB, the equation is as shown here.
Related formulasVariables
| Pr | power available at the input of the receiving antenna(in dBm) (dimensionless) |
| Pt | output power to the transmitting antenna(in dBm) (dimensionless) |
| Gt | antenna gain (with respect to an isotropic radiator) of the transmitting antennas (decibel) |
| Gr | antenna gain (with respect to an isotropic radiator) of (decibel) |
| λ | wavelength (m) |
| π | pi |
| R | distance between the antennas (m) |