User's Manual

megascan M1 User Manual Rev. 1.0 Updated on 28th August, 2009
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(This user manual / product specification is subjected to be changed without prior notice) P. 17
4.1.1 Radio Frequency Radiation Exposure
The highest RF output power of the unit was measured at 29.60dBm at 902.75
MHz. According to §1.1310 of the FCC rules, the power density limit for
General Population/Uncontrolled Exposure at 902.75 MHz is f (MHz) /1500 =
0.602mW/cm 2 . The
MPE is calculated to show the required separation distance that must be
maintained during installation to maintain compliance with the power density
limit. The minimum required cable length is 1.5m to be used with this device.
The following formula was used to calculate the Power Density:
S=
Where:
S = Power Density
P = Power input to the external antenna (Output power from the EUT antenna
Port
(dBm)
– cable loss
(dB)
)
G = Gain of Transmit Antenna (Linear gain)
R = Distance from Transmitting Antenna
The power density at 25cm separation is:
S=
For this device, the calculation is as follows:
P = 29.60dBm (Output power from the EUT antenna Port) – 0.75dB (Cable
Loss*)
= 28.85dBm (767.361mW)
*Cable Loss = (0.75dB) : 1.5m long of 0.5dB/m loss
G = Worst Case Antenna Gain = 6dB = anti-log(6.0/10) = 3.98
At 25cm separation,
S = ((767.361) x (3.98)) / (4π(25)
2
) = 0.389mW/cm
2
Based on the above calculation for 25cm separation, the power density does
not exceed FCC limit of 0.602mW/cm 2 .