Electronic tags are now widely used for identification and tracking objects. Tags also find uses in commercial products to mark their identity . The object tagged with the Electronic tag can be easily identified or located. The common type of tag used is the Radio Frequency Tag or RF Tag . Radio Frequency Identification ( RFID) is the technology used to transfer data from an Electronic Tag using radio frequency waves. The Tag called RFID Tag or RFID label is attached to an object and the data is collected in a RFID Reader to track the object. The signals from the Tag can be collected by the reader even if the Tag is located far away from the line-o-sight of the tag. The RFID tracking is a form of automatic identification technology using a unique serial number in the tag. RFID is widely used in biometric identification systems, domestic utilities, commercial items, security services etc for easy identification. Unlike Bar coding system, RFID does not require direct contact with the object and even it can identify the tagged objects placed in the body.
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How it Works?
RFID system essentially consists of three components like RF Tag, an Antenna and a Receiver or Reader.
The antenna emits radio signals to activate the tag and to read or write the data in the tag. The transmission range of the antenna range from one inch to 100 feet or more depending on the type and power output and the frequency of radio signals used. When the RFID tag passes through the electromagnetic zone, it receives the activation signal from the reader. The Reader captures the signals and transfers the same to the host computer for processing.
2. RFID Tag
RFID Tag or Transponder is a small and thin card with a silicon chip inside. The electronic circuit along with a spirally coiled antenna is present inside the card. The RFID Tag consists of a microchip which can store around 2 kb data. The data is send and received back between the Tag and the Reader. The Tag is activated by the reader to send or transmit the programmed data for a particular application through the radio waves. The RFID tag is a Transponder with programmed information for a particular application. The data from the Tag can be used for identification or location, specifications about products such as price, colour, date of manufacturing, date of purchase etc.
Types of RFID Tags
There are two types of RFID Tags. Passive tags and Active tags. Passive tags do not have a battery but the Active tag have battery on the board and the tag continuously transmits the signals. The Battery Assisted Passive tags (BAP) are also available which becomes active only in the presence of the RFID reader. The active tag encloses an integrated circuit for monitoring, modulating and demodulating the RF signals and an attached antenna for signal transmission and reception.
The Passive RFID Tag do not have a battery and the power is supplied by the RFID reader. When the RF signals hit on the antenna of the passive tag, a magnetic field develops and the tag obtains power from that magnetic field. The tag then transmits the encoded signal to the reader. The major disadvantage of the passive tag is that it can send the signal only if the reader is nearby and it is difficult to include electronic sensors that require continuous power. The advantage of the passive tag is that it has long durability around 20 years since there is no battery used. Moreover the size also too small to enclose in any product.
Chipless RFID tags do not have any integrated circuits to store information. Instead they use Fibers to reflect back the signals from the reader. The unique reflected signal can be used for identification. So Chipless tags are also called as RF fibers. The RF fibers can be in the form of fine threads, filaments labels or laminates. Chipless tags are less expensive and withstand environmental changes and are less sensitive to RF interference.
3. RFID Reader
RFID reader or Transceiver is the device used send and receives RF signals to the RFID tags. The reader can identify the information or unique data stored in the tag. A number of factors are important to achieve the Tag- Reader activities. This may include, read range, type of RF frequency and output power, orientation of the reader, placement of tag, antenna gain etc. Another problem in RFID reader is Reader Collision. This is the interference caused by more than one reader. The RF signals from two or more readers interfere each other and fail to communicate with the tag. To overcome this problem, TDMA (Time Division Multiple Access) technology is used in which the readers are programmed to read at different times. Tags may also read by different overlapping readers. To avoid this, the tags are programmed with a unique ID number to read once in a session.
Types of RFID Reader
There are two types of RFID reader based on the mobility. These are Fixed RFID and Mobile RFID Reader. If the Reader is stationary in a fixed position to read the tag, it is Fixed RFID and if the Reader is a moving one, it is Mobile RFID reader. Fixed Readers creates a specific zone around it with bubbles of RF energy. When the tag move in and out of the RF zone, the reader identifies the tag signals. Mobile RFID reader is used to attach with moving objects like vehicles and in hand held devices.