Radio Frequency Identification ( RFID ) is an automatic identification method, relying on storing and remotely retrieving data using devices called RFID tags or transponders . An RFID tag is a small object that can be attached to or incorporated into a product, animal, or person. RFID tags contain silicon chips and antennas to enable them to receive and respond to radio -frequency queries from an RFID transceiver . Passive tags require no internal power source, whereas active tags require a power source. Typical RFID tags usually can not store more than 2KB of data [22], limiting the amount of information that they can send.

The range of RFID tags range from just a few millimeters to several meters using passive tags (tags without their own energy source), to 100 meters or more with active tags (tags that are powered by an energy source). The range also depends on other factors, like the RFID reader used and interference. The transfer rate is also highly varying, depending on the implementation, frequency used, whether active tags or passive tags are used, and possibly other factors.

Types of RFID Tags:

RFID tags can be either passive , semi-passive (also known as semi-active ), or active .

• Passive: Passive RFID tags have no internal power supply. The minute electrical current induced in the antenna by the incoming radio frequency signal provides just enough power for the CMOS integrated circuit (IC) in the tag to power up and transmit a response. Most passive tags signal by backscattering the carrier signal from the reader. This means that the aerial (antenna) has to be designed to both collect power from the incoming signal and also to transmit the outbound backscatter signal. The response of a passive RFID tag is not just an ID number (GUID): tag chip can contain nonvolatile EEPROM(Electrically Erasable Programmable Read-Only Memory) for storing data. Lack of an onboard power supply means that the device can be quite small: commercially available products exist that can be embedded under the skin.

• Semi-passive: Semi-passive RFID tags are very similar to passive tags except for the addition of a small battery. This battery allows the tag IC to be constantly powered. This removes the need for the aerial to be designed to collect power from the incoming signal. Aerials can therefore be optimized for the backscattering signal. Semi-passive RFID tags are faster in response and therefore stronger in reading ratio compared to passive tags.

• Active: Unlike passive and semi-passive RFID tags, active RFID tags (also known as beacons ) have their own internal power source which is used to power any ICs and generate the outgoing signal. They are often called beacons because they broadcast their own signal. They may have longer range and larger memories than passive tags, as well as the ability to store additional information sent by the transceiver. To economize power consumption, many beacon concepts operate at fixed intervals. At present, the smallest active tags are about the size of a coin. Many active tags have practical ranges of tens of meters, and a battery life of up to 10 years.

Some applications of RFID are:

• Person Identification

• Food Production Control

• Vehicle Parking Monitoring

• Toxic Waste Monitoring

• Valuable Objects Insurance Identification

• Asset Management

• Access Control

• Mass transit ticketing

RFID References:

RFID Journal [1]

RFID News [2]

WikiPedia RFID [3]

What is RFID [4]

Sun Java and RFID [5]

RFID Tutorial [6]

RFID Beginners Guide [7]