Which technology is better—HF or UHF? This is not an easy question to answer because there are both business and technical issues that need to be considered. If you are installing a network of UHF interrogators for reading case and pallet tags, it might be cost-effective to use the same network to read item-level tags. But the distance from which you need to read the tags, the nature of the items you are tagging and the environment in which you are reading the tags will have an impact on which frequency you need to adopt.

For read distances beyond 6 feet, UHF is the clear winner. But for short read distances in difficult environments, such as on products containing water or metal, HF will perform better. And for long read distances in difficult environments, neither may work. In challenging environments, you may need to look at active tags (with batteries and transmitters) or semi-passive tags (with batteries but no transmitters), but these options are often more expensive than passive tags.

Rafsec and Symbol tag results: For its size, the Rafsec 3000518 was an excellent performer in terms of read distance. The Symbol I1030 had the worst overall performance. There are two large null zones in the E-plane of the Rafsec 3000518 (top left); the H-plane (top right) shows insensitivity to orientation. The Symbol I1030 shows two large null zones in the E-plane (bottom left); the tag will perform the same in the H-plane (bottom right), regardless of its rotation.

Conclusions
Item-level tags come in different sizes. Some are nearly 50 mm square, and some are as small as 15 mm by 35 mm. All other things being equal, in general, bigger tags perform better. But, interestingly, the second best-performing tag is also the smallest.

The performance of item-level tags is only a fraction of that of their larger case- and pallet-level cousins. We have read some case and pallet tags more than 30 feet away, for example, while two of the four item-level tags that we tested are virtually unreadable at 4 feet or more.

Keep in mind your requirements. If you need only 6 inches of read distance and can control the orientation, any of these tags might be suitable. But these tags were tested in free space, away from any interference. Performance can degrade when tags are placed on various materials, or if several tags are in close proximity (within a few inches). Also, there are manufacturing variances, so not all tags of the same model perform identically; you may need to plan on having some margin in the performance budget. (The results we present here are from a median-performing tag from a sample of at least 20 tags.)

Choosing among the four UHF RFID tags we tested will depend on many factors, and obviously, every application is different. The most common decision process is likely to be: Will the Alien ALL-9334 fit or is it too big? If it fits, use it. If not, can a null in the radiation pattern be managed? If not, the Avery AD-010 might be a better choice, since the Avery tag lacks two large null zones in any one plane, as is the case with the other tags. If so, then can a small failure rate be managed? If the answer is yes, the Rafsec 3000518 tag is probably the best choice; otherwise, the Symbol I1030 tag may work.


Daniel Deavours, Ph.D., is the research director of the RFID Alliance Lab, which is dedicated to unbiased testing of RFID products. The RFID Alliance Lab performs testing at the University of Kansas and is supported by Rush Tracking Systems of Lenexa, Kansas, and RFID Journal. To learn more about the lab, purchase reports or find out how the lab can help you with a special need, go to www.rfidjournal.com/labreports.