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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 71
Because there is a delay as the acoustic wave propagates through the tag and reflects back
to the reader, SAW tags operate in the SEQ communications mode. The reader broadcasts
its pulse and then waits, without needing to power the tag. The reader cannot really be
said to communicate with the tag since its interrogatory pulse is always the same. Think of
a SAW tag as if it were simply “shaped like” a particular number that the reader is able to
“illuminate” so that it becomes visible.
State Machines and Microprocessors
Some tags have more complex logic circuits than others. Most 1-bit tags and all SAW tags
have no logic circuits at all, while other types of tags have sophisticated state machines
incorporated into custom chips. An on-board state machine allows these tags to participate
in a complex anti-collision dance with the reader, which helps the reader to distinguish
individual tags from a large group of similar tags (For more on anti-collision, see
Chapter 4.)
More complicated processors can provide security through encryption or through control
sensors built into the chip. Advanced smart cards even have powerful microprocessors
that can be programmed and reprogrammed with new capabilities. As with memory
capacity, more processing capacity means a higher cost, so finding the right balance for a
given application can mean the difference between a profitable system and an expensive ...
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Publisher Resources

ISBN: 0596009445Catalog PageErrata