With the help of a mobile RFID computer, you can read all the clothing tags inside a cardboard box from across the room. But fill that box with cans of Coca-Cola, and you might not be able to read tags until you are inches away. How to solve these issues?
Author: Carl Michener
Radio frequency identification is quickly gaining prevalence in
the fashion apparel industry, as it is in major retailer supply
chain logistics. It's a technology that's superbly suited for high
product volumes and a high number of stock keeping units (SKUs),
but problematic when reading next to metals and liquids.
The big barrier to adopting the technology used to be cost. Less
than twenty years ago, tags cost tens and even hundreds of Euros,
limiting their use to tracking expensive assets like truck chassis,
tools and other equipment. Now some tags cost as little as a few
cents, making widespread use highly affordable. The biggest barrier
today is making low-cost tags that read properly next to metals and
Different ways UHF RFID reacts to reading around different
Efficiency = Superior data
"Just like with logistics, profitability in retail is closely
linked with efficiency," says Jorma Lalla, CEO of Nordic ID, a
Finnish manufacturer of RFID mobile computers. "And efficiency in
retail demands intimate data knowledge and transparency," he
continues. Tags can store great quantities of information
specific each individual item, and build a history as they travel
from manufacture to point of purchase or use. "RFID in retail
has produced tremendous results so far, and there are hundreds
more use cases waiting to happen."
In addition to serial number, colour, size, brand and other
product details, tags can accumulate information like ambient
temperature, time in, time out, and other data via an RFID reader
that has authorization to add or modify tag information.
Since RFID doesn't require line of sight to function, readers
installed in ceilings and floors can read passive tags at high
speed from distances of up to 8 metres. Every item on a pallet can
be automatically scanned and entered into an inventory system
as it is wheeled from trailer to warehouse…unless those items
are metal or contain liquid.
A tag is not a tag is not a tag
Metals detune and reflect RFID signals, while liquids absorb
them. This has historically caused poor tag read range,
unreliable reads, or no read whatsoever especially with Ultra
High Frequency (UHF) tags. UHF tags that read well next to
metal now exist, but they are not inexpensive.
UHF tags are not the only ones in use, but their advantages have
made them the gold standard.
Here are some of the differences between types of RFID
- UHF Ultra high frequency reading takes place in the 800 to 900
megahertz range. Reading is quick and covers distances of
eight to ten metres in the case of passive (non
batterypowered) tags. UHF has historically performed poorly in
reading metals and liquids.
- HF High frequency reading works much better than UHF with metal
objects and goods containing liquids, but is limited to a
distance of up to one metre.
- LF Low frequency reading is appropriate with read distances of
less than 30 centimetres. LF doesn't work well with metal, but does
work with beverage containers, produce and other items like
Active UHF RFID Active (battery-powered) UHF tags send out a
signal when they detect a properly configured RFID reader. They are
used to track items up to 30 metres away and more, depending on the
strength of the tag signal. Active tags are often used for high
value inventory such as military hardware and vehicles, aviation
equipment and some logistics processes.
Accurate reading near metals and
Clearly, inexpensive tags that can be read quickly and
accurately at a distance are the winner in most scenarios. The
ultimate tag is small, thin, inexpensive, tolerates chemicals,
water, reasonably high temperatures and rough handling-and its
readability is not affected by the presence of metal or water.
Figure out the metal and water part, and the rest is simple. Julian
Krenge, a researcher at the Institute for Industrial Management,
Aachen University in Germany, illustrates several options.
"One way to increase readability is to create a space of one
centimetre or more between the tag and the object it is affixed
to," says Krenge. He notes that such tags are bulky and relatively
expensive. Another experiment he conducted with some success was to
use regular 2D tags on a six-pack of plastic bottles of water. "If
you calculate the optimal position, choose the right type of tag
and pre-determine how the product is transported, readability can
be decent," he says, though he acknowledges that such a scenario is
not always practical.
A third option is to have the antenna rise vertically off the
tag. This works well, Krenge believes, "but it's not very practical
in most environments where goods are stacked beside and on top of
The key: integrating antenna design with chip
manufacture Professor Heikki Seppä-a senior research professor
with VTT and known in European scientific circles as Mr. RFID-is a
pioneer in the area and still pushing the boundaries of the
possible. He believes that the tag manufacturing process, not the
tag itself, is at issue.
"In close proximity to ferrous and most non-ferrous metals, you
have to use a 3D antenna in order to get a clear reading," says
Seppä. "That's being done now-it's quite simple-and the price of
materials to build the antenna is not much higher than for a 2D
metal tag. But the manufacturing process has yet to be properly
Seppä points to Traditional PIFA antennas (Planar Inverted
FAntenna) as the obvious technical solution to the problem.
However, the vias needed between the two conducting layers of the
antenna make the structure complex and expensive to manufacture.
It's not quite there yet, and as a result the cost per tag is still
Antenna manufacture and chip manufacture are separate
industries. For cost-efficiency to become a reality, the chip must
be embedded into the antenna layer in one simple, cost-effective
Like design, volume is crucial
Researchers like Seppä's team at VTT Technical Research Centre
of Finland are upping the ante in the RFID game by perfecting the
process of manufacturing tags-including thin, flexible tags-that
work with metal. These platform insensitive/platform tolerant and
platform-adaptive RFID tags are not innovative in the sense that
they make use of new technology, but rather in the way that they
are put together.
The team at VTT is set to enter the pilot phase of automating
manufacture. "We have settled on a fail proof method of automate
the manufacturing of 3D tags," says Seppä. "Now we need to invest
The VTT version of the simple 3D tags, which VTT is beginning to
market, is called 'PAFFA' for Planar Asymmetrically Fed Folded
Antenna. Traditional Planar Inverted FAntennas (PIFA) are a
technical solution for the problem, but the vias needed between the
two conducting layers of the antenna make the structure complex and
expensive to manufacture. The PAFFA solution replaces all of the
vias needed with a special antenna substrate folding technique. The
one critical via typically required at point of attachment to the
tag is replaced by a substitute circuit element. PAFFA type
antennas result in small tags that efficiently read over long
Economical 3D tags will be important to the advancement of many
industries. In automobile manufacturing, for instance, inserting
RFID into the value chain is the only way that companies can keep
up with the increasing demand for consumer personalization. Seppä
acknowledges that while volume is crucial to drive tag prices down,
it's also true that different products and applications will
require a specific configuration of tag.
This is the other impediment to high volume production of 3D
tags: the current heterogeneity of the RFID tag manufacturing
industry. Moving to 3D tags will mean more tag tailoring for each
customer. With PAFFA tags, customization is theoretically possible
even in the same production run. Bottles of juice will require more
inexpensive tags than those manufactured to track airplane wear
components. Tags will also require different configurations because
of the nature of the materials they are affixed to and the way that
those materials are transported and stored.
"My guess is we are three to five years away from more
widespread use of 3D tags," hazards Lalla of Nordic ID. "Demand is
growing, and it won't be long before it's satisfied. But it could
be a good while longer before we are tracking bottled water with 3D
For the article we interviewed: Mr. Jorma Lalla, CEO of
Nordic ID; Julian Krenge, Researcher at the Institute for
Industrial Management, Department of Information Management, RWTH
Aachen University in Aachen and Heikki Seppä, Senior research
professor with VTT Technical Research Centre of Finland located in
Espoo. VTT is a non-profit organization and the largest
multi-technological applied research organization in Northern