User Manual

OBID
i-scan
®
UHF
Installation
ID ISC.LRU3000/3500
FEIG ELECTRONIC GmbH Page 25 of 32 M21016-3e-ID-B
5.3.2. FCC-Reader according to FCC 47 Part 15
According to the FCC approval, Title 47, Part15 the maximum output power of the reader is limited
to 1 W (30dBm). The maximum radiated power of the antenna should not increase more then 4 W
e.i.r.p. Due to these facts two different cases have to be considered:
If a linear polarized antenna is used which gain is less then 6 dBi (factor 4), or if a circular polarized
antenna is used which gain is less then 9dBic the reader can always be configured to an output
power of 1W.
Antenna Gain < 6dBi → P
out
= 1 W
This would be the case if the FEIG standard antennas ANT.U170/170 -FCC (4dBic) or
ANT.U270/270 -FCC (8,7dBic) are used.
If an antenna is used which gain is more then 6dBi (9dBic) it is necessary to consider the antenna
gain and the attenuation of the antenna cable to calculate the right output power. If a circular polar-
ized antenna is used the antenna gain [G]=dBic can be reduced by 3dB. This is the case if the
FEIG standard antenna ANT.U600/270 -FCC is used. In this configuration the maximum output
power of the reader can be calculated in the following way.
P
Out
= 36 dBm (4 W e.i.r.p) – Antenna Gain (in dBi) + Cable Loss (in dB)
P
Out
= 36 dBm (4 W e.i.r.p) – Antenna Gain (in dBic) – 3 dB + Cable Loss (in dB)
The antenna gain of the circular polarized standard antenna ANT.U600/270 is 10,5 dBic. This
could be compared with a gain of 7,5 dBi of a linear polarized antenna (10,5 dBic – 3 dB).
Example 1:
Antenna ANT.U600/270 and 2 m Belden H155 Coaxial Cable:
P
out
= 36 dBm – 10,5 dBic + 3 dB + 0,6 dB
P
out
= 36 dBm – 7,5 dBi + 0,6 dB
P
out
= 29,1 dBm
Reader Configuration = 0,8 Watt
Example 2:
Antenna ANT.U600/270 and 6m Belden H155 Coaxial Cable:
P
out
= 36 dBm – 10,5 dBic + 3 dB + 1,8 dB
P
out
= 36 dBm – 7,5 dBi + 1,8 dB
P
out
= 30,3 dBm
Reader Configuration = 1,0 Watt
According to Example 2 it will only be necessary to adapt the output power of the reader when the
antenna ANT.U600/270 is used if the length of the antenna cable is less then 6m.