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Active Tags
Active tags are a subset of RFID tags that allow real-time
tracking of any object they are attached to. They are typically
used for applications like:
- Tracking very mobile objects - including personnel
in a facility, objects that are very mobile (like
warehouse loading equipment etc.), that need to be
actively tracked and monitored all the time.
- Tracking objects of very high value, that need “ubiquitous”
security without necessarily having personnel watching
over it all the time. An Active RFID solution is much
better than traditional CCTV solutions, primarily
because the system can be configured to trigger events
in the case of any anomalous behaviour, e.g. On any
movement.
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Technology
Active tags are self-powered - usually by a permanent voltage
source like an in-built battery. Other power sources like
solar powered (for outdoor use) tags are currently in developmet
at Analytica, for a variety of innovative uses. The voltage
source is used to periodically send out active RF signals,
broadcasting the ID of the tag to all available receivers,
from where it can be picked up by the (software) system to
“track” the tag.
Some of the newer tags have an in-built motion detector,
that broadcasts signals only when the tag is in motion - which
helps to extend the battery life for those tags very significantly.
Although tags usually broadcast their ID's, they can also
be designed to broadcast other useful information. For example,
some tags can have a temperature or pressure sensor built-in,
and can broadcast this information to RF sensors for “active”
control.
The RFID tags utilize electro magnetic energy to send signals
to program the transponder by switching the electro magnetic
field on and off. The duration of the on or off-phase defines
whether a low-bit or high-bit of information is being transmitted.
This technique of data transfer is called Pulse Width Modulation.
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