The third part of the article series Introduction to RFID technology takes a look at different types of tags. Tags are an essential part of an RFID system as they are used as an identifier for the product.
We have previously exhibited some RFID basics in
the first part of the article.
In the second part we discussed radio technology and radio
Different types of tags
A tag can come in various forms, depending on its purpose of use
and the frequency of the system.
There are three types of tags. Active and
semi-passive tags have an own power source and they are
often used in ports and harbors where long reading distances are
needed. Tags reporting temperature, which are used in the
horticultural, healthcare and grocery industry, also have their own
power source. The tags used in apparel are passive, which
means that they do not have their own power source. Instead, they
take all the needed energy from the reader through radio waves.
Whether the tag has its own power source or not also sets limits to
the reading distance, which varies from 10mm to 8m depending on the
reader in use and on the position of the tag. A passive tag is
rather cheap to produce, which is a great benefit for the apparel
industry, especially if the tags are not recyclable. In addition,
there are no remarkable differences in performance between these
tags. In addition to providing a product with a unique identity, a
tag can have other functions as well. A tag can i.eg be used for
reporting temperature as mentioned above, or for reporting
humidity, orientation or pressure.
EPCglobal (under GS1) has actively driven RFID
standards for tags. With the Gen-2 standard, EPCglobal managed to
create a single marketplace for UHF RFID systems and opened the
world to compatible and interoperable readers and tags. EPCglobal
classifies which protocol is used when a tag and a reader
communicate. The second-generation system of classification, Gen-2,
is designed for global operations. The basic idea of Gen-2 was that
products built according to the Gen-2 standard would work with each
other in any part of the world. The major regional regulatory
environments are taken into account in the way the standard defines
how the tags and readers use frequency and power. In addition,
Gen-2 provides increased speed for reading and writing tags for
supply chain operations, as well as the ability to function also in
dense reader environments such as in distribution centers,
warehouses and such. (Brown 2007)
Tag selection criteria
There is a wide range of tags used for apparel.
Typically the tags in apparel are divided into two groups: soft
tags and hard tags. Some of them are smart labels - stickers on
which the price information is printed. Some are hard smart pins
which are used as the counter-element of an electronic alarm, and
some can be sewn into the garment in the production phase and will
perhaps never be noticed by the consumer who purchases the
What is typical for all the UHF tags is the
structure. Each tag has a chip and a dipole antenna as can be seen
in the smart label tag inlay below. The chip which includes
the product information is in the center of the tag. The antenna
which assists in communication with the reader is horizontally in
both sides of the chip.
An example of a tag
inlay by Smartrac.
Another subject of discussion regarding tags is
whether they are reusable or not. Generally, smart labels and tags
placed on the products in the production phase which will remain
there (for instance a thin tag inside the side seams) cannot be
reused. Smart pin tags, on the contrary, can be removed from the
garment they have been attached to and be placed on a new item.
This needs of course changing the tag information in the back end
system, but with the systems that exist today that's not a trick to
do. The other benefit of the smart pin tag is the fact that the
counter-part of the pin is an EAS alarm. Therefore, smart pins are
very suitable for piloting in a store which uses an EAS system with
Practical tips for retailers
GS1 US-VICS has created guidelines for tag
placement in apparel retail. The manual provides wide instructions
about where the tag should hang in jeans, t-shirts, underwear and
accessories, for instance. The manual uses the current UPC tag
placement guideline as a starting point. Basically, the EPC should
be placed on media, trim, or packaging attached to the physical
garment itself so that the customer can remove it after purchase.
Alternatively, the tag can be separately affixed close to the UPC.
However, all the products in the same category or merchandise do
not necessarily have the same placement in men's, women's and
children's apparel. To reach optimal readability, there are five
certain placement options that should be avoided. Do not put the
- in places where the EPC tag to the place where the hanger clips
might go (the hanger clips may reduce readability)
- in places that are in contact with metal
- in places where the EPC tag might get folded
- directly onto to hanger
- loosely inside a package.
These kinds of guidelines help retailers to plan their tagging
processes so that the results of using the tags would be the
The fourth article of this series discusses
the readers and antennas. One more article to follow…
Brown, Dennis E. (2007) RFID Implementation. McGraw-Hill
VICS: Addendum to GS1 Apparel Guidelines: Format and Symbol
Placement regarding Electronic Product Code (EPC) Placement,