User's Manual

B-4 InterReach Fusion Wideband Installation, Operation, and Reference Manual
CONFIDENTIAL D-620616-0-20 Rev F
B.2 Human Exposure to RF
The U.S. Federal Communications Commission (FCC) has developed guidelines for
evaluation of human exposure to RF emissions. The guidelines incorporate limits for
Maximum Permissible Exposure (MPE) for power density of transmitters operating
at frequencies between 300 kHz and 100 GHz. Limits have been set for portable,
mobile, and fixed equipment. TE products fall in the category of fixed equipment;
products intended to be permanently secured and exposures are evaluated for dis-
tances greater than 20cm (7 7/8”). Portable devices fall into exposures of less than
20cm, are SAR evaluations are used.
Antenna gain is restricted to 1.5 W ERP (2.49 W EIRP) in order to satisfy RF expo-
sure compliance requirements. If higher than 1.5 W ERP, routine MPE evaluation is
needed. The antennas should be installed to provide at least 20 cm from all persons to
satisfy MPE requirements of FCC Part 2, 2.1091.
Basic MPE evaluation is performed by taking the maximum power output of the
equipment, the gain of the antenna to be used, and distance from the antenna, refer-
enced in FCC OET Bulletin 65 “Evaluation Compliance with FCC Guidelines for
Human Exposure to Radio Frequency for Electric Fields”.
TE products transmit well below the FCC power density limits. FCC defines power
output limits at 20cm distance for various frequency ranges:
• Over 300 mHz to 1.5 GHz the limit is determined by frequency/1500
• Above 1.5 GHz the limit is 1mW/cm2
The basic equation for determining power density is:
S = PG / 4R
2
Where S is power density in mW/cm2
PG, the transmitted power from the antenna identified as EIRP (Equivalent Isotropi-
cally Radiated Power), is the product of power output of device and antenna gain, in
mW.
R is the distance of interest from the antenna.
Typical Installation Example:
Assuming an antenna is placed on a 10 foot ceiling, for a person 6 feet tall, the dis-
tance from antenna to body is 4 feet (112 cm.).
For a PCS 1900 remote unit, the maximum power output, according to the power
table in Section 6.3 Maximum Output Power per Carrier on page 6-4, is 16.5 dB.
Assuming a 7 dBi antenna is used, PG in the equation is equal to 23.5 dB (224 mW)
EIRP.