With so much improvement in all three frequency ranges, it was becoming more difficult to choose the best frequency range for a specific application, particularly in choosing between HF and UHF.
Early in 2006, Deutsche Post World Net launched an initiative to evaluate industry usage of RFID across several industries including fashion, pharmaceutical and electronics. Other members of the DHL Innovation Initiative included IBM, Intel, Philips Semiconductors (now NXP Semiconductors) and SAP.
By including both HF and UHF systems in its testing and evaluations, the Initiative's goal was to determine optimum RFID solution for various applications within target industries.
Key factors being considered were the readability and writability of RFID tags under differing environmental conditions, when applied to the many materials found in a typical logistic environment.
Safety and privacy
Two important considerations for deployment of RFID systems are privacy and safety.
Privacy issues largely revolve around the range in which the RF signal can be read or written as well as the use of security enhancing technologies like password protection and cryptology and destroy commend where required.
Cryptology technologies are well proven and deployed at large for HF, some LF solutions but not yet in UHF solutions.
Since the power of HF RFID signals drops off rapidly from the interrogator antenna, it has an inherent advantage over the far-field operation of typical UHF RFID chips. UHF fields can, however, be contained by using near field coupling between the interrogator antenna and the tag—the technique used in the aforementioned NF UHF.
Health issues are still a matter of active study by regulatory agencies around the world. Allowable exposure is expressed in terms of power density. For a specific system with a known transmit power and frequency, this means that a minimum exposure distance can be calculated.
Regulatory bodies also make a distinction between allowable occupational exposure and allowable radiation exposure for the general public. Since the general public is not subject to more or less continuous exposure, the minimum distance is greater than for occupational exposure. Since NF UFH is a relatively new technology in terms of its use in RFID applications, it is not clear as of this time how the health issues will be sorted out.
Conclusion
Although the industry has, in the past, used LF or HF for item-level tagging and UHF for pallet and case-level tagging, NF UHF makes it possible to use NF UHF for item-level tagging. .
Initiatives to find the most cost effective technology for different applications are well underway. While technical efficiency is important, the studies also look at privacy, health, and security concerns that are often written into regulations.
There are also initiatives to harmonize a second-generation standard for HF, similar to the UHF Gen 2 standard already agreed to by EPCGlobal and ISO.
But it remains clear that there is no one-size-fits all solution for RFID. In countries where both HF and UHF frequencies can be utilized, issues such as tag performance repeatability, privacy, reliability, scalability and cost may tip the balance toward one frequency choice or the other. By making both available, system integrators have the option of determining the most appropriate solution and deploying it.
About the author
Jack Shandle is the site editor of WirelessNetDesignline. He holds BS in Electrical Enginering from the University of Pennsylvania and a MS in Communications from Temple University. Presently a freelance writer and editor, he formerly held management positions at several major electronics publications and can be reached at [email protected].
