RFID: How it works

History | How RFID works | Library Applications

How it works

There are two basic types of RFID devices which may be described as radio devices that respond with a radio signal in an automatic manner to exterior signals. Shien-Chiang Yu describes an RFID system as having three main components:

the RFID tag (or transponder);
the RFID reader (or interrogator); and
the application system which is used for the reader to transmit or receive data
from a tag

Active and Passive Tags

RFID tags have two main categories: active and passive. Active tags have a power source that is employed for the radio signal and data storage that is part of the tag. Passive tags rely on the energy from the radio signal provided by the reader or interrogator in order to transmit their own signal. If the design of the passive tag allows it may save data as well.

Examples of active tag applications are aircraft transponders used to identify their origin when prompted by a radar signal, tags attached to cars to allow automatic payment of tolls and devices attached to cars that through the use of Global Positioning System and cell phone technology allow the tracking of stolen vehicles.

A near field RFID tag

Passive Tags: Near Field and Far Field

Passive tags, which are well-suited to library tasks as they are much smaller and do not require a battery are in two distinct categories: near field and far field. These names suggest their ranges. The near field tag has a readable range of under a metre from the reader and gets power from the RFID reader through magnetic induction. The far field tag uses a higher radio frequency to communicate and collect power. Far field tags are effective up to 3 metres from the reader.

Types of Passive Tags and Capabilities

Shien-Chiang Yu describes four possible configurations for a passive RFID:

read only – records object’s identification number;
read/write – similar to memory cards, chips have a small amount of memory that is write-once, read-many (WORM) or is erasable and programmable;
built-in process chip – this type of tag is capable of processing information that is sent to it
system (OS) and programming, designed for high security use; includes processing capabilities and built-in sensor – for perhaps temperature or pressure sensors

Library Standard Tags

To date, the most common RFID tag configuration for libraries is a read-only, passive, near field tag using the 13.56 Mhz radio frequency.

Standards

RFID tags are subject to a number of standards. The ISO/IEC 15693, ISO/IEC 18000-3 Mode 1 and ISO/IEC 18000-3:2004 published, define tag operation. The NISO (NCIP) (draft approved awaiting publication) defines how RFID readers communicate with Integrated Library Systems.

History | How RFID works | Library Applications