Motorola PTP 600 System User Manual page 29

Peak power density in the far field of a radio frequency point source is calculated as follows:
=
S
Rearranging terms to solve for distance yields
2.1.1.1 Calculated Distances and Power Compliance Margins
T able 3 shows calculated minimum separation distances d, recommended distances and
9 5 9 H
resulting power compliance margins for each frequency band and antenna combination.
Band Antenna
2.5 GHz Integrated
5.4 GHz Integrated
Integrated
External
5.8 GHz
2ft Flat
Plate
External
6ft Dish
1. Calculated
Notes:
1. The regulations require that the power used for the calculations is the maximum power in
the transmit burst subject to allowance for source-based time-averaging.
2. At 5.4GHz the product is generally to a fixed EIRP which can be achieved with the
Integrated Antenna. If there are no EIRP limits, use the distance calculations for 5.8GHz.
3. At 5.8GHz, for antennas between 2ft and 6ft, alter the distance proportionally to the
antenna gain.
4. At 2.5GHz, with a 4/12ft dish, the safe distance is increased to 08/2.4m.
Where
P . G
π
2
4 d
d
Max Variable
Average
Transmit
P (Watt)
Power in
Burst
(Watt)
0.25 0.125 (18dBi)
0.005
(7dBm) 0.0025 (23dBi)
0.32
(25dBm) (23dBi)
0.16
0.32
(25dBm) 0.16 (28dBi)
0.32 6310
(25dBm) 0.16 (38dbi)
Table 3 - Power Compliance Margins
2
S = power density in W/m
P = Maximum Average transmit power capability of the radio, in W
G = total Tx gain as a factor, converted from dB
d = distance from point source, in m
P . G
=
π
4 . S
1
D (m)
G S
2
(W/m )
63
10 0.25
200
10 006
200
10 0.5
631
10 0.9
10 2.83
27
Recom- Power
mended Compliance
Distance Margin
(m)
2 8
1 16
2 4
4 4.5
10 3.5