Antenna #21. How to Use Friis Transmission Formula to Derive Free Space Path Loss (FSPL) Equation.

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Antenna #20. How to Derive the Friis Transmission Equation & Apply to Calculate Receiver Power, Pr.
   • Antenna #20. How to Derive the Friis Trans...  

In telecommunications, the free-space path loss (FSPL) (also known as free-space loss, FSL) is the decrease in signal strength of a signal traveling between two antennas on a line-of-sight path through free space. The "Standard Definitions of Terms for Antennas", IEEE Std 145-1993, defines free-space loss as "The loss between two isotropic radiators in free space, expressed as a power ratio."

𝐹𝑆𝑃𝐿=32.44 + 20 log f (MHz) + 20 log r (km)

Free-space path loss (FSPL) increases with the square of the distance between the antennas because radio waves spread out following the inverse square law. It decreases with the square of the wavelength of the radio waves and does not account for any power loss in the antennas themselves due to imperfections (such as resistance) or environmental interactions (such as atmospheric absorption).

FSPL is rarely used in isolation but rather as part of the Friis transmission formula, which incorporates antenna gain. It is a key factor in power link budgets for analyzing radio communication systems, ensuring sufficient signal strength reaches the receiver for intelligible transmission.

Define the concept of Free Space Propagation.

Free space assumes a channel free of all hindrances or obstacles to RF propagation such as absorption, reflection, refraction or diffraction. The energy arriving at the receiver is assumed to be only a function of the distance from the transmitter (following the inverse square law). A free space channel characterizes an ideal RF propagation path.