SECTION III: Understanding Radio Frequency IDentification (RFID)
HIGH FREQUENCY (HF) PASSIVE RFID
Passive high frequency (HF) operates at 13.56MHz and is a globally accepted frequency. This means that any system operating at HF can be used globally. However, there are some differences with regulations in the different regions of the world. These differences pertain primarily to power and bandwidth. In North America, Industry Canada (IC) and the FCC limit the reader antenna power to three watts while in Europe the regulations allow for four watts.
HF is also the basis of numerous standards such as ISO 14443, 15693, 18000-3. These standards and others will be discussed in more detail in section V on RFID STANDARDS.
With HF, the signal travels well through most materials including water and body tissue. It is however more affected by surrounding metals compared to Low frequency (LF).
In comparison to LF, the benefits of HF are lower tag costs, better communication speed and the ability to read multiple tags at once.
The length of the antenna is based on the length of the signal wave thus the higher the frequency, the shorter the wavelength. For this reason, there is the flexibility that an antenna for a HF tag is small enough that it can be produced by printing it onto a substrate, using conductive ink and then affixing the chip.
Tags produced with HF chips are typically less than 0.1mm in thickness and are available with different sizes of antennas. The larger the tag antenna, the greater the energy capture area the tag has and the greater the communication distance from the reader. Smaller tag sizes may be easier to package into a product but the downside is the reduction of communication distance available.
The capability of the small inlay size allows for it to be embedded into labels. Labels with inlays are called smart labels. Through the use of printers with embedded RFID or external readers, smart labels can not only be printed on; they can also be written to.
With the current power regulations, HF is designed for applications that require a 0.1mm or less of communication range. Orientation of the tags with respect to the reader antenna will have an impact on the communication range. For optimum communication range, both antennas (tag and reader) should be parallel. Having the tag perpendicular to the reader antenna may significantly reduce the communication range.
The higher the frequency, the higher the data throughput and the faster the communication will be between the reader and the tags. This increase in speed allows for the reader to communicate with multiple tags at once. The process of communication with multiple tags is known as anti-collision and at HF, a reader can read more than 50 tags per second.
The following are some of the benefits and limitations of HF RFID:
- Penetrates most materials well including water and body tissue
- Not as effective as LF in the presence of metal and water
- Tags can easily be embedded into non-metallic items such as labels, pallets, key tags, cards etc.
- HF should not be affected by electrical noise that may be generated by motors in an industrial environment
- Higher data transfer rate (20ms for read command), the higher the frequency, the faster the communication
- Transponder are less expensive
- Reader can communicate with multiple tags simultaneously
- Read range is less than one meter
- Tags have larger memory capacity
- Frequency is recognized and used globally (no restrictions)
- Global standard: ISO 15693, 14443A, 14443B, 18000-3
- HF is also the frequency for NFC (Near Field Communication)
HF is also used for access control and security systems. The additional memory allows for improved security and the integration of biometrics as part of the security features. Enhanced access control systems have the ability to validate assets such as office equipment, i.e., computer equipment and other items as one passes through an access control system or portal. Assets embedded with a HF tag can be read and identified within the access control system. Documents and files can easily be identified and tracked as well.
Contact-less smart cards or RFID cards are going to be the next generation of credit cards. Credit card companies have been testing HF RFID based on ISO 14443 standards for some time. One of the main reasons for the switch to contact-less smart cards is primarily due to the ruggedness and consistent performance levels associated with RFID. When a tag is embedded into a card or other form factors, the tag is essentially protected from the surrounding environment. As for the readers, they can also be encased and protected from the surrounding environment. The second reason for the switch to RFID is the additional memory the tags can store. This allows for better security and protection of privacy issues. By using biometrics and personalized access numbers, improved security can be accomplished.
From a computing/communications infrastructure point of view, smart cards provide localized intelligence that enables distributed computing whereby transactions can be authorized and performed without continuous direct communication and intervention from a centralized backend server. Increased memory, security (encryption) and processing at user card interface reduces network traffic with this delegated local responsibility.
In Hong Kong, more than nine million people use the Octopus card to access their public transit system. The city of Toronto and surrounding municipalities have introduced a transit payment system, called Presto, based on ISO 14443, for payment and access to all transit systems in the area. This will allow travelers to move seamlessly between trains, light rail, metro and buses within the Toronto and greater area using one single, contact-less ticketing solution.
Numerous sports teams and events are using HF RFID for payment and access. Most ski hills in Europe use the technology for convenience and for prevention from fraud. Large events such as the Olympics and the world cup have used tickets embedded with HF inlays.
HF is also a solution for identifying products, such as cases and pallets. The communication range of HF limits the type of warehouse or logistics applications. For retail or for applications that do not require long communication distances, HF is a very good solution.
High Frequency RFID is an ideal solution for applications that require lower cost identification and the ability to read multiple tags at once at a distance of one meter or less.
Continue reading…click here for Section IV: ULTRA HIGH FREQUENCY (UHF) PASSIVE RFID