2
Theoretical Bounds on Re?¬‚ection Coef?¬?cients
(R??1300 V, C??1.1 pF)
Region Theoretical Bound on jGjDv
United States 1.443106
Europe 2.4231051
Japan 1.1831076
Australia 1.0431019
All regions 0.032
74 RFID Handbook: Applications, Technology, Security, and Privacy
Even a carton of photocopy paper may prove problematic for RFID labeling because
the liquid that affects RFID performance does not have to be an actual liquid. Paper
typically has high moisture content, and it does absorb RF energy. Wooden pallets made
with green or indeed anything but oven-dried wood present the same challenge because
of the moisture content. Fresh fruits and vegetables and frozen items will also pose
liquid-related problems for RFID. It is important to evaluate whether the items have the
potential to hold or attract moisture when considering the design of RFID tag antennas for
tagging the items.
Metal is perhaps more of a challenge because it may either re?¬‚ect or absorb electromagnetic
waves. However, the behavior of electromagnetic waves next to a metal surface is
predictable as opposed to the effects mentioned previously. In certain situations,
the presence of metal can actually improve the performance of an RFID tag. Irregular
metal, on the other hand, will either absorb the signal or re?¬‚ect it in random directions.
Metallized foil bags and even antistatic bags can act as metal.
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