Friis Transmission Equation

Friis Transmission Equation Calculator

Calculate the received power in a wireless transmission using the Friis transmission equation. Input the frequency and distance to determine the free-space path loss and Fresnel zone radius.

Note: The Friis transmission equation calculates the power received by an antenna under idealized conditions given another antenna some distance away transmitting a known amount of power.

About the Friis Transmission Equation

The Friis transmission equation relates the power received by an antenna to the power transmitted by another antenna, separated by some distance. The equation accounts for antenna gains and the wavelength of the signal.

Formula:

Pr / Pt = Gt × Gr × (λ / 4πR)²

Where:

  • Pr = Power at the receiving antenna
  • Pt = Output power of transmitting antenna
  • Gr = Gain of the receiving antenna
  • Gt = Gain of the transmitting antenna
  • λ = Wavelength
  • R = Distance between antennas

Fresnel Zone: The Fresnel zone is an ellipsoidal region between the transmitting and receiving antennas. This calculator computes the radius at the center point, which is critical for determining whether obstacles will interfere with the signal.