RFID Tag - Credit Card Datasheet

1023_1_Product_Manual created: 10/12/07 Page 8
Technical Section
RFID
RFID (radio frequency identification)
systems use data strings stored
inside RFID tags (or transponders) to
uniquely identify people or objects when
they are scanned by an RFID reader.
These types of systems are found in
many applications such as passport
protection, animal identification,
inventory control systems, and secure
access control systems.
RFID Protocols
In order for an RFID reader like the
PhidgetRFID to communicate with an RFID tag, they must share a common protocol. This
protocol acts as a set of rules for the way data is transmitted wirelessly between the reader
and tag. The PhidgetRFID (as well as RFID tags sold by Phidgets) uses the EM4102 protocol.
Any other tags that also use the EM4102 protocol can be used with the PhidgetRFID.
Communication and Effectiveness
RFID tags come in two main varieties: passive and active. Active tags have their own power
supply which they use to power an antenna to communicate and transmit data. Passive tags
derive the power they require to operate directly from the RF output of the RFID reader, and
no other power supply is necessary. This makes passive tags cheaper to produce and easier
to implement.
Because passive tags require a strong RF field to operate, their effective range is limited to an
area in close proximity to the RFID reader. In the case of the PhidgetRFID, tags brought within
approximately 3” of the reader can be read. The distance over which the RFID tag is usable
is affected by such things as the tag shape and size, materials being used in the area near
the reader, and the orientation of the reader and tag in respect to each other and in their
operating environment. The smaller a tag, the closer it must be to the reader to operate.
Multiple Readers
Multiple PhidgerRFIDs within 1 to 2 meters may
interfere with eachother. This can be overcome
in software by enabling the antennae of individual
PhidgetRFID readers in sequence.
Starting with all readers disabled, enable the 1.
antenna of the first PhidgetRFID reader.
Wait for 100ms or more to detect any tags.2.
Disable the antenna of the first reader and enable 3.
the antenna of the second, and perform another
wait cycle.