Inductive coupling requires that the reader close the tag

Working with RFID Tags • Chapter 3 67

You have already seen in this chapter how the read range depends on the tag type and the operating frequency. The maximum allowed power that an antenna can emit comes from standards and regulations. The higher the power, the larger the read range. The read range also depends on which of the following two communication techniques your RFID system is using:

Tags are placed on the items that need to be identifi ed and tracked. Before you can place a tag, that is, attach a tag to an item, it needs to be in a form so that it can be conveniently attached to the item. Creating that form is called labeling the tag. In other words, to tag an item is a three-step process:

■ Manufacture the tag (a combination of IC, antenna, and substrate).

68 Chapter 3 • Working with RFID Tags

which it can be conveniently attached to an item. What form (e.g., size and shape) a tag will take depends on the following factors:

The inlay is the bare-bones tag discussed in this chapter so far—that is, the combination of antenna, chip, and substrate. The inlay needs to be packaged (labeled) before use.

Insert

Smart Labels

A smart label is a barcode label that has an embedded RFID tag inside it. You can print human-readable, useful information on the label face, such as sender’s address, destination address, and product information. A smart label has the following components:

the pressure-sensitive inlay into rolls for easy and safe distribution. This layer can later be removed to place the smart label on an item.

RFID-enabled tickets are inserted into paper or plastic envelopes that are directly attached to the items that need to be identifi ed. The paper or plastic material used for these envelopes should be ultraviolet-resistant—that is, transparent to UHF waves. Several types of polypropylene, polyester, polyethylene, and polyethylene terephthalate (PET) fi lms are good selections and offer low attenuation for UHF waves.

Tie-On Tags

70 Chapter 3 • Working with RFID Tags

Selecting Adhesive Types for Tags

■ Ease and strength of initial tack

■ Time it takes the bond to form the full strength

Placing a Tag

Placing tags on the items can be challenging. There are no global guidelines regarding where on the items the tags should be placed. It depends on the application, item, and environment.

Corrugated cardboard

Refl ection, multiple paths
Absorption, detuning, refl ection

Shadowing is caused when an item, say B, is behind another item, say A, from the perspective of the reader. In this case, a signal from the reader will be received only by A. The item B will get little or no signal and will be missed by the reader. Item B, in this situation, is said to be shadowed by item A. If the items inside a package or the cases on a pallet are densely packed, the reader will miss some of them.

NOTE