Radio frequency identification (RFID) is an advanced automatic identification technology. It uses radio frequency signals to acquire data remotely from tags within read (or “interrogation”) range. read range. A typical RFID system contains several
components including an RFID tag, which is the
identification device attached to the item to be tracked,
and an RFID reader and antenna, which are devices that
can recognize the presence of RFID tags and read the
information stored on them. After receiving the
information, in order to process the transmission of
information between the reader and other applications,
RFID middleware is needed, which is software that
facilitates the communication between the system and the
As shown in Figure 1 below, a typical RFID system is made up of several basic components: tags, reader, antennas and the host computer system.
Figure 1: Basic Components of an RFID System
Tags – RF tags are devices that contain identification and other information that can be communicated to a reader from a distance. The tag comprises a simple silicon microchip attached to a small flat aerial and mounted on a substrate. Tags are often classified as either passive or active to describe how they communicate with the reader. A passive tag reflects the RF signal transmitted by the reader and embeds its unique ID and data by modulating that reflected signal. An active tag contains a battery that can actively transmit data to a reader.
Reader – The reader, sometimes called an interrogator, sends and receives RF data to and from the tag via antennas. It contains transmitter, receiver and microprocessor. The reader unit also contains an antenna as part of the entire system.
Antennas – The antenna broadcasts the RF signals generated inside the reader’s transmitter into the immediate environment. It also receives responses from tags within range.
Host computer system – The data acquired by the readers is then passed to a host computer, which may run specialist RFID software or middleware to filter the data and route it to the correct application, to be processed into useful information.
The radio frequency is the determining factor for the type of application an RFID system is best suited for. Basically, the radio frequencies can be classified as shown in Table 1.
Table 1: Comparison of RFID Frequency Band and Their Respective Applications
Types of RFID Tags
RFID tags are microchips that contain identification and
other information that can be communicated to a reader
from a distance. Accordingly, a tag can store a unique
identification number electronically that identifies the
specific item to which the tag is attached. RFID tags can
be divided into three main types with respect to the source
of energy used to power them:
Active Tags - Use a battery to power the tag transmitter
and receiver to broadcast their own signals to readers
within the life of batteries. This allows them to
communicate over distances of several meters.
Semi-passive Tags - Contain built-in batteries to power the
chip’s circuitry, resist interference and circumvent a lack
of power from the reader signal due to long distance. They
are different from active tags in that they only transmit
data at the time a response is received.
Passive Tags - Derive their power from the field generated
by the reader without having an active transmitter to
transfer the information stored.