RFID operate over several frequency ranges.,br>
- Low-frequency (LF): 125 to 134.2 kHz and 140 to 148.5 kHz. Typical applications include immobilization systems in automobiles, retail, and animal identification and it's tracking through the human food chain.
- High-frequency (HF): 13.56 MHz. Typical applications include tagging of rental items like books or uniforms, public transportation ticketing pharmaceuticals and other item tagging.
- Ultra-high-frequency (UHF): 860 MHz to 960 MHz. Typical applications include fixed asset tracking, baggage handling, and supply chain applications.
Standards
Although organizations such as EPC Global and AIM/ are involved in standardizing physical and system attributes, there is no global public body that governs the frequencies used for RFID on a world wide basis.
As a result, countries and regions have chosen independently which frequency bands are reserved for the use of RFID. LF and HF RFID tags can be used globally, with power levels harmonized on a global basis simplifying the desing of labels and readers.
For UHF frequencies, however, the situation is a bit more challenging. The heavily used frequency range of 860 MHz to 960 MHz was chosen for UHF RFID and this is creating challenges for the unified solutions. It will be no easy task to get the approval for the usage of RFID at UHF in all countries. But without a global standard, UHF companies that operate on a global scale will struggle to implement it cost effectively.
Multiple frequencies, varied applications
LF and HF frequencies have been heavily utilized for RFID rollouts utilizing passive systems. Standardized LF and HF technologies have been available since 1995, while UHF has been available since 2001.
LF systems have an advantage in applications that have harsh operating conditions. High immunity to electrical noise and encryption technology are two decided advantages. A range of 1.5 metres can be reached. LF is also suitable applications involving liquids, organic materials and metals because it does not scatter when it meets these surfaces.
LF is already the major technology in: animal identification, access control, asset management solutions for gas cylinder, beer kegs and other high valued products. LF's range, performance and cost are being improved with new IC designs and more mature readers in the market.
An HF system is considered appropriate in applications where items are tagged and read/ write ranges of up to 1.5 metres are required. Encryption algorithms allow for protected data on the IC and EAS features in the tag, make anti theft prevention possible.
Typical applications today include tagging of library books, CDs and DVDs, pharmaceutical products for counterfeit prevention and many applications which require a very precise read and write environment.
New encryption algorithms are being used in HF to make the technology even more secure for short ranges. Faster protocols are being introduced to improve the reading and anti-collision speed. Additionally, new regulations are being worked on to allow for more power to be used to increase the read and write distance of the HF solutions.
UHF RFID
UHF is typically used for applications where of several meters are required. These include pallet and case identification in warehouses, as well as car authentication in a factory for production control purposes.
In the UHF space, only Far Field UHF technology has been available until recently, making identification of fluids and other organic material virtually impossible. Today the industry is working on Near-Field UHF (NF UHF) to get around these problems. With NF UHF, read distances of approximately 30 cm can be achieved, allowing for some item level tagging.
Figure 1 provides an overview of the performance of LF, HF, and UHF systems across several key areas. Tag construction will be discussed in the next few paragraphs.
Click here for Figure 2
Figure 2: Metals, field characteristics and tag construction are challenging for NF UHF.
Whereas HF and LF tags tend to have typical coil configurations that allow generic label designs, UHF tags come in many different configurations as they need to be optimized to the material the labels to which they are attached. This is largely due to the fact that UHF signals interact with tagged articles or adjacent materials more than HF or LF.
FF UHF is well characterized but work continues on optimizing hardware and software to solve application specific requirements. These include improving read rates, optimizing reader fields and working on the harmonization of regulations to allow UHF to be used on a world wide basis.
In 2006, work began on NF UHF has to analyze how it can be used to achieve item-level tagging.
