MM-010539-001, Rev. P6G
15
1.8.2.2 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 M/A-COM 4.9 GHz VIDA Broadband Client specifications:
P
: Maximum Peak Conducted Power = 27 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 = 4.94 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( 0.5 W * G
N
/ (4 * 3.1415926 * 10
) )
R
min
= 1.26 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 M/A-COM 4.9 GHz VIDA Broadband Client. The user should always keep a
safe distance from antenna greater than 20 cm or SQRT (3.9789E-3 * G
N
).
The following table lists fixed installation’s minimum distance for different Effective Antenna Gain
Levels (Antenna Gain – Feeder Cable Loss). In all cases, the minimum safe distance defined in Table 1-2
or 0.2 meters (8 inches), whichever is greater, is the recommended minimum safe distance for fixed
installations.
Table 1-2: MPE Minimum Distance Calculation for Fixed Client Installations Using High Gain Antennas
Low Power Fixed Clients (0.1 Watts)
High Power Fixed Clients (0.5 Watts)
Effective
Antenna Gain
(dBi)
Minimum Safe
Distance (Meters)
Minimum Safe
Distance (Feet)
Minimum Safe
Distance (Meters)
Minimum Safe
Distance (Feet)
<10
0.20 0.65 0.20 0.65
11 0.20 0.65 0.22 0.73
12 0.20 0.65 0.25 0.82
13 0.20 0.65 0.28 0.92
14 0.20 0.65 0.32 1.04
15 0.20 0.65 0.35 1.16
16 0.20 0.65 0.40 1.31
17 0.20 0.65 0.45 1.47
18 0.22 0.73 0.50 1.64
19 0.25 0.82 0.56 1.84
20 0.28 0.92 0.63 2.07
21 0.32 1.04 0.71 2.32
22 0.35 1.16 0.79 2.61
23 0.40 1.31 0.89 2.92
24 0.45 1.47 1.00 3.28
25 0.50 1.64 1.12 3.68
26 0.56 1.84 1.26 4.13
>26
Reduce Transmitter Power as required by FCC
