RFID Arena


BOMBPROOF RFID - Smart RFID tag manufacturing makes reading next to metals and liquids a reality

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 liquids.

RFID Reading Reflections

Different ways UHF RFID reacts to reading around different materials. 

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 reading:

  • 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 that

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 liquids

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 each other."

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 automated."

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 high."

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 process.

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 in tooling."

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 distances.

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 tags."


Interviewees -in -the -article

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 Europe.

3 comments on “BOMBPROOF RFID - Smart RFID tag manufacturing makes reading next to metals and liquids a reality”

  1. Gravatar of Hanna ÖstmanHanna Östman
    Posted 19 July 2013 at 13:11:41

    This article was also published in Data Collection magazine:


  2. Gravatar of MahmoudMahmoud
    Posted 16 March 2015 at 10:22:22

    please can you explain what you mean by "3D antenna"?!

  3. Gravatar of Suvi DalénSuvi Dalén
    Posted 26 March 2015 at 12:25:41

    Hello Mahmoud,

    in this context the 3D antenna means a manufacturing technology which enables producing thin tags working on metal and liquids.

Post a comment

Keep in touch

Send me more info!
Send me a Newsletter!
Send me a Magazine!
Contact info