For example, if the maximum read range of a reader is 5 m using 2 W
ERP (shown in Figure 7.8), and if a read range of only 2 m is required, the required
radiated power can be lowered to 0.32 W ERP. This estimation may not be accurate in
real life due to complex electromagnetic propagation phenomena, such as re?¬‚ection caused
by the surroundings objects, but it demonstrates that power reduction is a viable option.
7.6.2 Reduction of Overall Reader Talking Time
While it is possible to talk for 4 s, reader applications should be con?¬?gured to talk for only
the time necessary to capture tag data. There is no optimum talking time. It depends on the
application and also the surroundings of the deployment zone. On-site ?¬?ne-tuning and
measurements are needed before the reduction of talking time can be carried out.
7.6.3 Use of External Sensors
Sensors can be used to turn RFID readers on only when tags are approaching to further
reduce reader interference in that area. This will free up the channels allocated for those
antennas, and also avoid unnecessary interference to other surrounding reader antennas.
For example, external sensors can be attached to the dock door in the case study in Section
7.5. When the dock door is not in use, the designated RFID readers would be switched off,
as shown in Figure 7.9. Optionally, the central control unit can then dynamically shift the
channels assigned for the antennas at door 3 to door 4 as shown.
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