User's Manual

20
4. Software
In the European approval area, the radiated power must not exceed 2 W ERP. This fi 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
- 2.14 dB
G
HW
... Gain referred to half-wave dipole
G
isot
... Gain referred to 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 transmission power can be increased by 3 dB.
G
HW
= G
isot
- 2.14 dB - 3 dB
G
HW
... Gain referred to half-wave dipole
G
isot
... Gain referred to isotropic radiator in dBic
- In the FCC 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, the RF power connected must be reduced
correspondingly
- The reader's transmission power is then:
P
Reader
= P
cond
+ D
Cable
, with P
cond
≤ 1 W and G
isot
≤ 6 dB
P
Reader
... Reader's transmission power in dBm
D
Cable
... Cable attenuation
G
isot
... Gain of the antenna in dBi
P
cond
... Power at the antenna input in dBm
If the antenna gain is stated in dBic, the reader's transmission power can be increased by 3 dB.
The transmission power for the European variant can be set in 0.25 dB steps from 20 dBm to 33 dBm.
Kanalwahl (Channel selection)
The reader transmits, dependent on the approval region, in the frequency range 865 MHz to 868 MHz
for Europe or 902 MHz to 928 MHz for USA. In Europe the number of channels to be used can be
limited. For this purpose the related check box must be selected on the “verfügbare Kanäle” (Available
channels) list for each channel the reader is to use. In this manner it is possible to avoid from the start
the usage of specifi c channels on which there is interference. In the case of a read command, the
reader searches for a spare transmission channel using LBT (Listen Before Talk). The reader starts
to search through the channels in ascending order. As soon as it fi nds a free transmission channel,
the reader starts to send its data on this channel.