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Chapter 3
CHAPTER THREE
Tags
HE PURPOSE OF AN RFID TAG IS TO PHYSICALLY ATTACH DATA ABOUT AN OBJECT (ITEM) to that item.
Each tag has some internal mechanism for storing data and a way of communicating that
data. Figure 3-1 shows diagrams of several representative RFID tags.
Not every sort of RFID tag has a microchip or a built-in power source, but every RFID tag
has a coil or antenna of some sort.
While it is important to realize what all tags have in common, classifying tags helps in
understanding how they work. In this chapter, we will categorize RFID tags by those crite-
ria most likely to affect the capabilities of the tag within our applications. We will divide
tags based on their physical characteristics, their air interfaces (how they communicate
with readers), and their information storage and processing capacity. With these criteria in
mind, we will then explore some of the standards that define these variations and talk
about guidelines for matching tags to applications. We’ll start by looking at some basic tag
capabilities before launching into the discussion of tag categories.
Basic Tag Capabilities
Many basic operations can be performed with an RFID tag, but only two of them are
universal.
T