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Easy to use and convenient, RFID is a flexible technology that is well-suited for automatic operation.
A basic RFID system has several primary components. The 'tag' which contains an antenna, some type of transmitter and some computer memory program with an identity. The 'reader' is a microcontroller which accepts the information and passes it along to a computer data base for interpretation.
For example, in a proximity access control system, the card takes the place of a key, and contains a coil of wires which access both a transmit and receive antenna. It includes an integrated circuit or 'chip' preprogrammed with a unique code for identification. When the card comes within the 'proximity' of the reader, the chip is powered by an RF signal and transmits its identification. The reader sends the identification to the host database verifies it and signals the electronic door lock to allow access. No direct contact is necessary between the card and a reader.
RFID tags can vary significantly in size, shape and weight, frequency and memory depending on the intended use. Some tags are as small as 10 cent piece and some are comparable to the size and weight of a credit card.
There are two basic types of RFID tags:
Passive RFID tags. Passive RFID tags can be as small as 0.3mm and don't require batteries. Rather, they are powered by the radio signal of a RFID reader, which "wakes them up" to request a reply. Semi-passive RFID tags contain a small battery that boosts the read range. Passive tags are generally read-only; meaning the data they contain cannot be altered or written over.
Active RFID tags. Active RFID tags, also called transponders because they contain a transmitter that is always "on", are powered by a battery, about the size of a coin, and are designed for communications up to 30 meters from the RFID reader. They are larger and more expensive than passive RFID tags, but can hold more data about the product. Active RFID tags may be read-write, meaning data they contain can be written over.
- Low frequency with a range of 125-148KHz
- High frequency at 13.56 MHz
- Ultra-high frequency at 868-930 MHz
- Microwave at 2.45 & 5.8 GHz
Low-frequency tags are used for applications such as car locks, pet and farm animal identification. High frequency tags are used for library book identification, security access and asset management. Low and High frequency RFID are limited to shorter read ranges. Ultra-high-frequency tags are used for applications such warehouse tracking for boxes, pallets and containers and can usually read up to 7 metres and Microwave tags are used for highway toll-collection and railroad car tracking, which require much longer read ranges of up to 30 metres.
Unlike bar codes, which need to be scanned manually and read individually (you have to actually see a bar code in order to read it); RFID tags do not require line-of-sight for reading. Within the field of a wireless reading device, it is possible to automatically read hundreds of tags a second. Not only can these tags be read faster than bar codes, they also contain more information, so they can recall items more efficiently.
RFID has the ability to track every item anywhere in the supply chain in real time, eliminating human error. Instead of typing information into a database or scanning the wrong bar code, goods will communicate directly with inventory systems. Readers installed in factories, distribution centres, store rooms and on store shelves will automatically record the movement of goods from the production line to the consumer.
RFID tags can be installed in clothing labels, packaging, books...the applications for this technology are seemingly endless.
The frequency range selection is usually governed by how quickly a tag must pass by a reader and/or distance requirement between the reader and the tag.