The RFID Tagging Guide: Secrets For Handling Difficult To Read Products By ODIN Technologies
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One of the critical elements of every RFID system is the tag. The tag must be able to communicate clearly with reader antennas for the system to work. If it does not, no data is received or recorded. Without the data exchange between tags and readers the entire system fails no matter how expertly it is architected.
Typical RFID readers include several configuration controls that adjust the reader's ability to communicate with tags. By contrast, tags have no such configuration controls. The key parameters you can adjust to improve tag communication is which tag design you select, and where and how it is applied to the item being tracked.
The physics of Radio Frequency determines tag performance
The complication arises because different tags work differently with different product materials. The
materials in close proximity to tags can interfere with tag communication performance. For example, in
the UHF spectrum where most DoD, Wal-mart and Target applications operate, RF waves are reflected
by metals and absorbed by liquids. These materials and others directly degrade tag communication
performance and are measurable based on the physics of radio frequency. However, certain locations
on a product or specific tag designs may provide much better performance than others. This is why tag
selection, or SKU testing as it is commonly called, receives so much attention.
To design a properly functioning RFID system, you must identify appropriate tag and location combinations for the product SKU. For products with RF friendly materials such as paper the process is more forgiving than for RF unfriendly materials such as metal and water. Many early adopters of RFID still rely on trial and error testing methods to identify tag and location combinations. This approach is time consuming, costly and unlikely to yield desirable results.
Establishing a scientific process based on physics is critical to success
End users should adopt a scientific process to identify the best tag and location combinations for the
products they wish to track. In order to successfully achieve this goal a basic understanding of the
physics involved in testing products for RFID tag performance is helpful. Adopting a scientific approach
will help you identify solutions for difficult to tag items, and create a common procedure that is
applicable across frequencies and various regulatory environments. Understanding these important test
principles will also help you avoid the mistakes and misperceptions all too common among RFID end
users today.
RFID is not Black Magic – it is predictable
It is clear from our experience that many end users still think RFID is black magic. For example, I was
recently with a client demonstrating a software tool designed to discover the best tag selection, position
and orientation combination on a given stock-keeping unit (SKU). We were testing one of their difficult
to read SKU's (high in water content) and in this case the design and placement of the tag was not
carefully selected leading naturally to poor performance. The client assumed that because the
interrogation antenna had line of sight with the tag we would instantly achieve favorable results. With
difficult to read objects, scientific testing has to be executed to ensure success.
While RFID promises to achieve automated, non-line of site communication, this can only be achieved in many cases by carefully tuning key system parameters including tag selection and placement. ODIN technologies has developed a scientific methodology and tool set that leverages the physics of RFID to properly determine the right tag and location combination for each application and product type. Our experience confirms that trial and error methods such as conveyor testing are costly and often produce spurious results, while frequency response characterization provides cost effective and scientifically sound results. The underlying physics of ODIN technologies' approach is based on frequency dependency of RFID systems which other techniques ignore.