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fspl

Free space path loss

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Syntax

L = fspl(R,lambda)

Description

example

L= fspl(R,lambda)returns the free space path loss in decibels for a waveform with wavelengthlambdapropagated over a distance ofRmeters. The minimum value ofLis zero, indicating no path loss.

Examples

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Open Live Script

Calculate the free-space path loss (in dB) of a 10 GHz radar signal over a distance of 10 km.

fc = 10.0e9; lambda = physconst('LightSpeed')/fc; R = 10e3; L = fspl(R,lambda)
L = 132.4478

Input Arguments

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Units are in meters.

Wavelength units are meters.

Output Arguments

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Whenlambdais a scalar,Lhas the same dimensions asR.

More About

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Free Space Path Loss

The free-space path loss,L, in decibels is:

L = 20 log 10 ( 4 π R λ )

This formula assumes that the target is in the far-field of the transmitting element or array. In the near-field, the free-space path loss formula is not valid and can result in a loss smaller than 0 dB, equivalent to a signal gain. For this reason, the loss is set to 0 dB for range valuesR ≤ λ/4π.

References

[1] Proakis, J.Digital Communications. New York: McGraw-Hill, 2001.

Extended Capabilities

See Also

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Introduced in R2017b

Communications Toolbox Documentation

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Bridging Wireless Communications Design and Testing with MATLAB

Bridging Wireless Communications Design and Testing with MATLAB

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