3.5 Performance Measure
While addressing the topic of RFID label antenna design, it is important to consider the
practical performances of such antennas when attached to an RFID label IC. The accepted
metric for such performance comparisons involves taking a read range measurement. The
read range of a tag is the maximum distance between a reader antenna and the tag before
the reader fails to decode the tag responses while the tag antenna is favorably oriented
to the reader antenna propagation ?¬?eld. These read range measurements may be taken in
TABLE 4.3
Theoretical Bounds on Re?¬‚ection Coef?¬?cients
(R??2500 V, C??500 fF)
Region Theoretical Bound on jGjDv
United States 2.083107
Europe 1.2431058
Japan 1.3831087
Australia 1.9331022
All regions 0.0014
Far-Field Tag Antenna Design Methodology 75
an anechoic chamber, or may be performed in a more practical environment where the tag
is to be deployed.
In the theoretical estimation of read range for systems operating in the UHF spectrum,
two scenarios can be analyzed. These are
. Tag power constrained analysis
. Reader sensitivity constrained analysis
In the tag power constrained analysis, it is assumed that the system is adequately designed
so that the sensitivity of the interrogator??™s RF receiver is not a limiting factor (this might be
the case in the event of a reader using a bistatic antenna con?¬?guration).
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