RFID is not new, one of its original uses being the identification of friendly aircraft during the
Second World War. Until recently the technology was viewed as being too expensive and too
limited in functionality for most commercial applications. Advances in technology have both
reduced the cost of individual system components and provided increased capabilities, to the
point where numerous organizations are either using or considering using RFID technology. In
fact, some organizations, notably Wal-Mart and the US Defense Department, have mandated the
use of RFID by their business partners.
RFID is made up of three components: a transponder or tag, a reader or interrogator and the
necessary supporting infrastructure such a communications hardware and software. The RFID
tag, which in most cases, consists of a chip and antenna mounted onto a substrate or an
enclosure. In the chip is a processor, memory and radio transmitter. These transponders/tags
communicate via radio frequency to a reader, which has its own antennas. The readers can
interface through a wired or a wireless medium to a main computer. Transponders/tags are also
known as smart or radio tags. The memory will vary, depending on the manufacturer, from just a
few characters to even kilobytes. Transponders can either be read only (R/O) that are preprogrammed with a unique identification or read write (R/W) for applications that require data to be stored in the transponder and can be updated dynamically. Another type of transponder is written once read many times (WORM). This will allow for an identification number to be written to the transponder once. Here information is stored in the memory and while it cannot be
changed, the transponder can be read many times.
The two primary types of RFID technologies are active and passive. Active RFID transponders
are self-powered and are more expensive than passive. Self-powered active tags to have greater
communication distance and usually larger memory capacity than passive tags. A common
application for active RFID is called AVI (automatic vehicle identification) and found on major
Passive RFID transponders have no internal power source and require external power to operate
(Figure 1). A transponder/tag is powered in one of two ways: inductive coupling or back-splatter.
Low-frequency and High-frequency tags are powered using inductive coupling where an
electromagnetic signal is transmitted from a reader. The signal received will charge an internal
capacitor on the transponder, which in turn, will then supply the energy required to communicate
with the reader.