Page 6 - Microwave and mmWave Interference Best Practices
P. 6
Fresnel Zone Clearance
The Fresnel Zone is an ellipsoid that
goes between two antennas (A & B). The
border is determined to be half the
wavelength at any point (C).
A common rule used is that in
order to have a wave propagation behave
as it would in “free space,” there should be
st
a t least 60% of the 1 Fresnel zone clear
of any obstruction. In the case a reflection
occurs in an even Fresnel zone and is
received, the signal will then be out of
phase and reductive. If the reflection
happens in an odd zone the signal received
will be in phase and additive to the
received signal. Other considerations that
must be made, especially when the
distance covered is over about 5 miles. As
the earth is round the curvature must be
considered, as well as any obstruction that
may be infrastructure or terrain.
Atmospheric refraction may also cause the
signal to be degraded.
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