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RFID Essentials
book

RFID Essentials

by Bill Glover, Himanshu Bhatt
January 2006
Intermediate to advanced content levelIntermediate to advanced
278 pages
12h 2m
English
O'Reilly Media, Inc.
Content preview from RFID Essentials
TAGS 63
Coupling
A tag’s coupling mechanism determines the way a circuit on the tag and a circuit on the
reader influence each other to send and receive information or power. The type of cou-
pling a tag uses directly affects the read range between the tag and reader. We can group
the different read ranges loosely into those systems where the read range is close (within 1
cm), remote (1 cm to 1 m), or long-range (more than 1m). A synonym for remote coupling
is “vicinity coupling.” In this section, we will discuss backscatter coupling, inductive cou-
pling, magnetic coupling, and capacitive coupling. Capacitive and magnetic coupling are
examples of close coupling, inductive coupling is a type of remote coupling, and backscat-
ter coupling may be remote to long-range.
Along with range, the choice of coupling mechanism strongly affects which frequency the
tag should use. Inductive coupling typically works best in either the LF or HF range. Back-
scatter coupling works better with higher frequencies. Magnetic coupling is most efficient
at 1–10 MHz, and capacitive coupling usually runs at about 10 MHz to provide a fast
enough clock for communications and processing.
RFID coupling, especially in the case of passive tags, may seem a bit mysterious at first.
How can a tiny tag with no battery participate in a radio conversation? Let’s find out.
Backscatter coupling
Backscatter coupling provides an elegant ...
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Publisher Resources

ISBN: 0596009445Catalog PageErrata