User's Manual

Page 84 of 105 User Manual | SRU-8X1X RFID Reader 18000-63
Doc No. 47000001740
|
Version 01
|
2018-12-11
|
released
Confidential
14.7.1 Port Power
In Europe, the radiated power is limited in accordance with ETSI 302208 to 2 W ERP. In the FCC/IC region,
max. 1 W connected RF power applies with an antenna gain of 6 dBi. If the antenna gain is greater than 6
dBi, it is necessary to reduce the RF power accordingly. While the European standard refers to a half-wave
dipole, FCC part 15/RSS 210 refers to an isotropic radiator.
To set the port power, it is necessary to include the length-dependent cable attenuation and the antenna gain
into the calculation of the port power. An example for the calculation of the port power for Europe and
FCC/IC is given below.
The following applies to the European approval region:
P
port
= P
ERP
+ D
cable
– G
HW
,
where P
port
is the port power of the reader in dBm; P
ERP
is the port power based on a half-wave dipole
in dBm; D
cable
is the cable attenuation in dB; G
HW
is the antenna gain based on a half-wave dipole.
The cable attenuation is the length-dependent attenuation of the cable at the related frequency:
D
cable
= l*D
dB/m
,
where D
cable
is the cable attenuation in dB; I is the length in m; D
dB/m
is the attenuation in dB/m at frequency.
The antenna gain is stated in various different units. These units include dBi and dBic. The units dBi
and dBic refer to an isotropic (spherical) radiator, where dBic refers to a circularly polarized isotropic
radiator and dBi to a linearly polarized isotropic radiator.
In the European approval area, the radiated power must not exceed 2 W ERP. This figure refers to
a half-wave dipole. The relationship shown below exists between an isotropic radiator (dBi) and a
half-wave dipole.
G
HW
= G
isot
– 2.14 dB,
where G
HW
is gain-based on a half-wave dipole and G
isot
is gain-based on an isotropic radiator in dBi
If the gain of the antenna is referred to the polarisation of a circular isotropic antenna (dBic), the
linear gain of the antenna is 3 dB lower. As a result ,the port power can be increased by 3 dB.
G
HW
= G
isot
– 2.14 dB – 3dB,
where G
HW
is gain-based on a half-wave dipole and G
isot
is gain-based on an isotropic radiator in dBi
In the FCC/IC approval region, the RF power connected at the antenna input must not exceed 1 W. If
the gain of the antenna is higher than 6 dBi, it is necessary to reduce the RF power correspondingly.
The reader's port power is then:
P
port
= P
cond
+ D
Kabel
with P
cond
 1W and G
isot
 6dB,
where P
port
is the port power of the reader in dBm; P
cond
is the power on antenna output in dBm; D
cable
is the cable attenuation in dBm; G
HW
is the antenna gain in dBi.
If the antenna gain is stated in dBic, the reader's transmission power can be increased by 3 dB. The port
power for the European variant can be set in 0.25dB steps from 6 dBm to 33 dBm.