User Manual

MM-018965-001
10
1.3.2.2 MPE Calculation for Directional Antenna
This MPE Minimum Distance Calculation is based on using a directional antenna with more than 9 dBi
antenna gain.
Basic Harris 4.9 GHz VIDA Broadband Client specifications:
P: Maximum Peak Conducted Power = 30 dBm
G: Maximum Omni Antenna Gain – Cable Loss = 27 dBi – 1 dB = 26 dBi; (Use numerical G
N
value
for the calculation ): G
N
= 10 ^ (G /10); For G = 26 dBi, G
N
= 10 ^ (26 /10) = 398
Frequency Range = 4.90 to 4.99 GHz
R
min
: Minimum Distance between user and antenna to comply with FCC MPE Level (10 W / m
2
)
Equation from FCC:
P
d
= P * G
N
/ ( 4 * π * R
min
2
)
R
min
= SQRT [ 1.0 W * G
N
/ (4 * 3.1415926 * 10 ) ]
R
min
= 1.78 m, for G =26 (i.e., G
N
= 398 )
The calculation provides guidelines for users to estimate the minimum safe distance when a high gain
antenna is connected to the 4.9 GHz VIDA Broadband Client. The user should always keep a safe
distance from antenna greater than 30 cm or SQRT (3.9789E-3 * G
N
).
The following table lists fixed installation’s minimum distance for different Effective Antenna System
Gain Levels (Antenna Gain – Feeder Cable Loss). In all cases, the minimum safe distance defined in
Table 1-1 (Clients Stations), or 0.3 meters (12 inches), whichever is greater, is the recommended
minimum safe distance for fixed installations.
Table 1-1: MPE Minimum Distance Calculation for Fixed Client Installations Using High Gain Antennas
Effective
Antenna Gain
(dBi)
Fixed Clients (1 Watt)
Minimum Safe
Distance (Meters)
Minimum Safe
Distance (Feet)
<10
0.30
0.98
11
0.32
1.04
12
0.36
1.17
13
0.40
1.31
14
0.45
1.47
15
0.50
1.65
16
0.56
1.85
17
0.63
2.07
18
0.71
2.32
19
0.80
2.61
20
0.89
2.93
21
1.00
3.28
22
1.12
3.68
23
1.26
4.13
24
1.41
4.64
25
1.59
5.20
26
1.78
5.84
>26
Reduce Transmitter Power as required by
FCC