GE MDS 4710M, Техническое руководство

Страница: 106 / 113

102 MDS™ Master Station MDS 05-6399A01, Rev. E
ƒ = frequency in GHz
Fresnel Zone Boundary
where:
F
n
= Fresnel zone boundary in meters
d
1
= distance from one end of the path to the Fresnel zone boundary (in kilometers)
d
2
= distance from the other end of the path to the Fresnel zone boundary (in kilometers)
D = total path distance (d
1
+d
2
) in kilometers
ƒ = frequency in GHz
n = Fresnel zone, 1 (for 1st) is used here
Theoretical Signal Strength
where:
RSSI = signal strength at the receiver in dBm
EIRP = RF power output in dBm + G
ta
–L
tfl
α
fs
= free-space path loss in dB
G
ra
= receive antenna gain in dBi
L
rfl
= receive feedline loss in dB
L
tfl
= transmit feedline loss in dB
G
ta
= transmit antenna gain in dBi
Probability of System Fading
where:
FProb = probability of fading more than F
a = terrain factor
- 4 is used for very smooth terrain, such as over water
- 1 is used for average terrain, with moderate roughness
- 0.25 is used for mountainous or very rough terrain
b = climate factor
- 0.5 is used for a hot, humid climate
- 0.25 is used for temperate or northern areas
- 0.125 is used for a very dry climate
ƒ = frequency in GHz
d = path length in km
F = fade margin in dB
F
n
nd
1
d
2
⋅
fD
-------------------- 17.3
=
R SSI EIR P
α
–
fs
G
ra
L
rfl
– + =
FP rob a b 6.0 10
7
–
f d
3
10
F
–
( )
10
⁄
× × × × × ×
=