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RFID Technology with passive TAG
FALCON system for car identification and vehicles
registration (EVR) operates with passive tag RFID
technology which has significant advantages
comparing with active TAG, since passive TAGs are
cheaper, robust, autonomous in operation and do not
require maintenance. This enables TAG power supply
technique through electromagnetic field which also
serves for wireless data transfer. Passive TAG
consists of: antenna, electronic switch, bulk
capacitor and logic circuit. At first, when TAG is
in EM field of an adequate frequency, the potential
at the ends of the antenna is used for saving energy
in the bulk capacitor. When bulk capacitor voltage
increases over certain value, TAG electronics starts
operating and through switcher it implements short
links of the antenna ends in the rhythm of binary
signal in the TAG memory. These impulses, of main
frequency several periods, interrupt EM field and
through antenna receiver RFID reader recognizes it
as binary signal with modulated amplitude. Detection
of signal reveals series of binary signals relevant
for data in TAG memory.
TAG construction
In order to ensure optimal results and depending on
possible TAG installation into the vehicle, three
constructions are applied. The first one, with
maximum robustness is TAG in its own plastic casing
which ensures optimal results when mounted on metal
surfaces. The second TAG type in the form of
sticker, designed to be applied on the glass
(usually windshield glass, behind rearview mirror)
must not be stuck on metal surfaces. In cases when
any of these two installations is not adequate
(motors, motor trailers, temporary TAG use) TAG
plastic card is used.
TAG speed
For RFID technology in vehicle registration, very
important factor is TAG maximum relative speed,
comparing with RFID reader. Increase of this speed
is provided, primarily with the efficiency of energy
transfer system from EM field into TAG, the increase
of frequency modulation of the basic TAG holder (256
kB), as well as its more frequent call. In real
conditions recorded speeds were over 160 km/h
(theoretically up to 250 km/h).
RFID reader
The reader consists of special antennas and reader
electronic. Proper results are provided with 2
antennas, the first to make EM field of exact
frequency and the second as a receiver and it
records every change, i.e. EM field modulation
caused by TAG. With a circle polarisation of
antennas records are more reliable in various
positions of Tag antennas. The reader itself ensures
normal operation on all standard defined ISM
channels, from 864 MHz to 869 MHz. Radiation power
can be changed, from 0.5 W EIRP when reliable
readings up to 3 m are provided, up to 2 W EIRP for
distances up to 10 m. The reader itself enables
filtering of frequent TAG recall, by the user, since
one TAG can have several hundreds of calls per
second. Also, TAGs that are not in database can be
filtered. Owing to UHF technology and efficient
signal processing reading speed is up to 200 various
TAGs per second. The reader can operate also as
stand-alone device when the activation of external
devices (relays, locks, motors) is is performed
through control exits. Readers and antennas
construction satisfies the most strict stnadards
concerning protection against weather influence.
Interference problems and security
Interference occurs in 2 forms: between 2 (and more)
RFID readers and between 2 (and more) TAGs.
Interference between 2 readers is solved so that
each reader operates only 10% of time, so that there
is always a period of "silence" when operation of
another, competitive reader is possible, even on the
same frequency i.e. channel. Interference between
TAGs is solved in a way that each TAG switch on is
done randomly, by the implemented random generator.
Each TAG has its own unique factory series number
(up to 128 bits) so that cloning is almost
impossible.
Data Collection
Through series RS232 port on RFID reader data on
registered vehicle can be sent to server directly to
COM port or through some of the converters (COM to
USB or RS232 to Ethernet). Also, it is possible to
provide economical data transfer by wireless network
(GPRS) for devices that are pretty far from the
server. For connection and control of RFID reader to
PC unique application "Falcon Service Application"
is used, which can connect 1 or several readers by
virtual COM ports. Configuration of virtual ports,
operation mode of some readers, data filtering mode,
server and database choice, etc. is done by
configuration XML file. At this way it is possible
to form unique database (SQL sever) on all
registered vehicles.
TAG Registration Database
Data on registration, stored in database are as
follows: ID of registered TAG, date and time of
registration, ID of the reader registered by TAG and
finally, events probability when the readers operate
in pair. Further data processing in "TAG
Registration Database" depends on the type and needs
of end-user. |
