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Design and Optimization of Passive UHF RFID Systems (Hardcover, 2007 ed.)
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Design and Optimization of Passive UHF RFID Systems (Hardcover, 2007 ed.)
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Radio Frequency IDentification (RFID) is an automatic
identification method, relying on storing and remotely retrieving
data using devices called RFID tags or transponders. An RFID tag is
a small object that can be attached to or incorporated into a
product, animal or person. RFID tag contains antenna to enable it
to receive and respond to Radio-Frequency (RF) queries from an RFID
reader or interrogator. Passive tags require no internal power
source, whereas active tags require a power source. As of today
(2005), the ubiquitous computing and ambient intelligence ideas are
making their way. In order for these to become a reality, a number
of key technologies are required. Briey, these technologies need to
be sensitive, responsive, interconnected, contextualised,
transparent and intelligent. RFID is such a technology and more
particularly passive RFID tags. But, in order to deliver the
necessary characteristics that could trigger ambient intelligence,
there are some challenges that need to be addressed. Remote
powering of the tags is probably the most important. that allows
the RF signal to be converted to Direct Current (DC) are in pole
position. Secondly, the communication link and the reader should be
optimized. The RF signal that contains the tag data suffers from a
power of four decay with the distance between tag and reader. As a
result, both the reader sensitivity and the tag backscattered power
efficiency have to be maximized. Long-range powering, as well as
sufficient communication quality, are the guidelines of this work.
This research project proposes a linear two-port model for an
N-stage modified-Greinacher full wave rectifier. It predicts the
overall conversion efficiency at low power levels where the diodes
are operating near their threshold voltage. The output electrical
behavior of the rectifier is calculated as a function of the
received power and the antenna parameters. Moreover, the two-port
parameters values are computed for particular input voltages and
output currents for the complete N-stage rectifier circuit using
only the measured I-V and C-V characteristics of a single diode.
impedance modulation at the tag side affects the signal at the
reader. The method allows the tag designer to efficiently predict
the effect of modulator design at system level and gives an useful
instrument to choose the most appropriate impedances. Finally, the
design of a fully integrated remotely powered and addressable RFID
tag working at 2.45 GHz is described. The achieved operating range
at 4 W Effective Isotropically Radiated Power (EIRP) reader
transmit power is 12 m. The Integrated Circuit (IC) is implemented
in a 0.5 silicon-on-sapphire technology. A state of the art
rectifier design achieving 37 per cent of global efficiency is
embedded to supply energy to the transponder. Inductive matching
and a folded-dipole antenna are key elements to achieve these
performances. Thenecessary input power to operate the transponder
is about 2.7.
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