About RFID

Radio Frequency IDentification (RFID) technology is about the remote collection of information stored on tags using radio communication. It provides a non 'line of sight' interface between the physical and data management environments. Tag information can range from a simple identity or licence plate to thousands of bytes of data. Information is written to or read from tags using a radio transceiver called a reader (interrogator). The reader may be a handheld unit or a fixed unit connected to a remote computer system. Most systems for item identification operate on the principle of passive backscatter; in other words the tag operates on the principle of radar relying on the reader to provide the energy required for communication.

RFID system operating range and performance depends on a number of factors.

• Operating frequency
• RF power output of the reader - this generally depends on the local radio regulations
• Size of the Tag
• Material composition of the item to which the tag is attached
• Whether the tag has battery assistance.

Operating frequency

The particular frequency is usually chosen to suit the desired system characteristics. Lower frequencies generally provide better penetration through non-metallic materials which have a high moisture content but relatively short operating range and more expensive tags. Higher frequencies (UHF range) provide limited penetration but much longer operating ranges. The most common, though not the only frequencies generally available for RFID use are LF (nominally 132 kHz), HF (13.56 MHz), UHF (860 - 960 MHz) and microwave (2.45 GHz and 5.8 GHz).

Passive/Active Tags
There are two broad categories of tags; Passive tags and Active tags. Passive tags do not transmit a signal but rely on the reader to provide the carrier wave for backscatter modulation as well as the energy to power the tag circuits. They may optionally incorporate a battery to help boost the operating range. Active tags always have their own power source and contain a transmitter.

Read Range
Read range depends on whether the tag is an active or passive tag. Passive tags have relatively short read ranges whereas active tags have much longer read ranges. LF and HF systems use induction communication with read range in the order of less than 2 metres. UHF and microwave systems use propagating waves and can have operating ranges of up to 10 metres for passive tags and 100 metres of more in the case of active systems.

Anti-Collision
Anti-collision schemes within the various air interface protocols allow readers to arbitrate and read a plurality of tags present within a reader field; for example multiple items in a basket of goods at a supermarket.

Standards
Standardisation provides a means for different users and manufacturers to produce tags which are interoperable. The International Organisation for Standardisation ISO, has published the 18000 family of RFID standards covering a range frequency bands and application requirements. EAN International and UCC established EPCglobal to produce a standard for consumer product tagging.

Comparison Table >>