3.1.1 Tags
Tags are attached to all objects to be identified in an RFID system. A tag is typically
composed of an antenna or coupling element, and integrated circuitry. An important
distinction that will be discussed later is a tag’s power source. Often tags carry no on-board
power source and must passively harvest all energy from an RF signal.
There are many types of tags that offer different functionalities, have different power
sources, or operate at different radio frequencies. Each of these variables helps determine
which applications a particular tag may be appropriate for and what the costs of a tag may
be. These differences will be discussed further in Section 3.2.
Modern tags tend to implement identification functionality on an integrated circuit (IC) that
provides computation and storage. In the manufacturing process, this IC is attached or
“strapped” to an antenna before being packaged in a form factor, like a glass capsule or foil
inlay, that is integrated into a final product.
In practice, different vendors often perform each of these manufacturing steps. Other RFID
designs may be “chipless” or have identifying information hard-wired at fabrication time, i.e.
“write-once, read-many” tags. Newer technologies that allow RFID circuitry to be printed
directly onto a product will be discussed in Section 5.