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Showing posts from June, 2014

Path Loss Models for Microwave Links Unraveled

Free Space Model

     The free space model only accounts for the loss in signal power due to spreading of energy over a 3-dimensional space.

FSPL of FSL = (4*pi*f*d/c)^2

f - frequency
d - distance
c - speed of light
Wavelength (lambda) - c/f

     We notice from the formula that as the frequency increases, the loss becomes greater, which is intuitive since more wavelengths are needed to cover a given distance compared to the lower frequency wavelengths. Naturally, as the distance increases, the loss becomes greater as well.

ITU Terrain Model

     This model considers the Fresnel zone, aside from the free space loss at distances (-20*Cn+10) and closer (where Cn is the normalized terrain clearance).

Total Loss = -20*Cn + 10 + FSL

Cn = (h1-h2)/sqrt((lambda*d1*d2/(d1+d2)));
h1 - height of LOS link
h2 - height of obstruction
d1 - distance to obstruction from TX 1
d2 - distance to obstruction from TX 2
lambda - wavelength

Weissberger's Model

Total Loss = FSL + 1.33*(f^0.284)*(d^…