Samitha's Tech Blog: RFID - Radio frequency Identification

As the name implies, Radio frequency Identification (RFID) means the process that identifying objects by means of radio waves. A special device is used to identify the object uniquely, and is called as RFID tag or Radio tag. More precisely this is the process of relying on storing and remotely retrieving data using RFID tags. Nowadays this tag become very small and can be implanted to a product, an animal or even to a person for the purpose of identification by means of radio waves.

Commonly available RFID tag has two major parts. One is an integrated circuit for storing and processing information, modulating and demodulating a radio frequency (RF) signal and perhaps other specialized functions. The second is an antenna for receiving and transmitting the signal. RFID increases the speed and accuracy with which inventory can be tracked and managed thereby saving money for the business.

RFID tags come in three general varieties named as passive, semi-passive (also known as battery-assisted), or active.

Passive RFID tags

These types of RFID tags have no internal power supply to energize its internal circuitry. In the instance that a RFID reader emits its radio waves, the induced electrical current in the antenna of the tag produces the required power for the CMOS IC in the tag. From this, the tag transmits its response to reader. This means that the antenna has to be designed to both collect powers from the incoming signal and also to transmit the outbound backscatter signal. The response of a passive RFID tag is not necessarily just an ID number or a code similar to bar code; the tag chip can contain non-volatile EEPROM for storing data.

The practical read distance of a passive tag has the range of 10 cm to few meters, and it depends on the operating radio frequency, the type of antenna, the size of it and the design of RFID. The lack of an onboard power supply means that the device can be quite small: commercially available products exist that can be embedded in a sticker, or under the skin in the case of low frequency RFID tags.

In February 2007 Hitachi Cooperation announced a RFID device measuring 0.05×0.05 mm, and thins enough to be embedded in a sheet of paper. This is named as µ-Chip. Silicon on insulator (SOI) was used to achieve this integration level of the chip. The new chips can store as much data as the older tags, and the data contained on them can be extracted from as far away as a few hundred meters. This chips can wirelessly transmit a 128 bit unique ID and data (encrypted or not), which is embedded to it in manufacturing process.

Active RFID tags

Active type RFID tags have their own internal power source to energize their integrated circuit module and transmit the signals to the tag reader. Active tags have the ability to conduct a session with the reader by using a handshaking technique. Also these types of tags have the ability of transmitting higher signal power levels to the reader because of its onboard power supply. This feature leads to more effective operation rather than passive tags in environments like water, metal (shipping containers, vehicles), or at longer distances. Many active tags have practical ranges of hundreds of meters, and a battery life of 5 to 10 years. Active tags typically have much longer range (approximately 100 m/300 feet) and larger memories than passive tags, as well as the ability to store additional information sent by the transceiver.

Semi Passive RFID tags

Semi-passive tags are similar to active tags as they have their own power source, but the battery is used just to power the microchip and not broadcast a signal. The RF energy is reflected back to the reader like a passive tag.

http://www.hitechno.info/2007/06/operation-of-rfid-tag-example.html

http://www.hitechno.info/2007/06/applications-of-rfid-tags.html

http://www.hitechno.info/2007/06/problems-of-rfid-tags.html

http://www.hitechno.info/2007/06/new-trends-in-rfid.html