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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 RFID devices.

Basic Components

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.

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Frequency Band

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

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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.

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