User's Guide
112 of 146
Operating the Reader Using the ReaderStart Software
16.7.1 Port Power
In Europe, the radiated power is limited in accordance with ETSI 302208 to 2W ERP. In the FCC/IC region, max. 1W
connected RF power applies with an antenna gain of 6 dBi. If the antenna gain is greater than 6dBi, 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 dierent units. These units include dBi and dBic. The units dBi and dBic refer to an
isotropic (spherical) radiator, where dBic refers to a circularly polarised isotropic radiator and dBi to a linearly polarised
isotropic radiator.
In the European approval area, the radiated power must not exceed 2W ERP. This gure 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
– 2.14dB,
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 3dB lower. As a result ,the port power can be increased by 3dB.
G
HW
= G
isot
– 2.14dB – 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 1W. If the gain of the
antenna is higher than 6dBi, 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 3dB.
The port power for the European variant can be set in 0.25-dB steps from 6dBm to 33dBm.