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Q2.
How to calculate the minimum mounting height
of the devices?
In order to maximize the received signal strength of the
devices, you need to minimize the effect of the
out-of-phase signals, which is caused by obstacles in the
path between the transmitter and the receiver. Fresnel
Zone is a usual method to calculate this path, as shown in
the formula and the figure below.
H h+r * (1 40%)
(H is the height of the CPE)
d
d
c
1
2
r
d
d
f
1
2
For example, assume d1 is 2km, d2 is 8km, and f is 2.4GHz,
then r would be 14.142m. Considering a toleration of 40%,
allowable radius would be 8.485m. Assume h is 10m, then
the result of the minimum mounting height based on this
point would be 18.485m. Similarly, calculate the results
based on all the points where there are obstacles, and the
maximum value would be the final result.
For more information, please refer to:
http://en.wikipedia.org/wiki/Fresnel_zone
d2
d1
r
h = the height of
obstacle at this point
where,
r = Fresnel zone radius in meters
c = 3x108 m/s, speed of light
f = operating frequency of the
devices in Hz
d1 & d2 = the distances between the
point and the devices in meters
21
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