RFID

• RFID (radio frequency identification) allows data to be transmitted wirelessly over radio waves.
• There are two parts to an RFID system: a tag and a reader. Use of radio signals means that the system does not require a line of sight between the tag and the reader.
• RFID tags are made up of an antenna, for receiving and transmitting the radio frequency signals, and a chip, which processes the signals. Each tag has a unique identifier and will often store some additional data in a non-volatile memory cell.
• The RFID reader transmits an encoded radio signal to interrogate the tag. The tag receives the message and then responds with its identifier and any other stored data (for example, a stock number or product ID). Readers can process multiple tags at the same time as each has a unique identifier.
• RFID tags can be read-only or read-write, and come in many physical forms. For example:

  • They can be incorporated into tiny sticky 'labels' that can be concealed within products
  • They are often embedded in employee and student ID cards that are used to open doors and car park barriers
  • They are used in many library cards and on transport systems
  • They are commonplace on production lines and in warehouses
  • They are used to track the movements of farm animals, and pet owners are often encouraged or required to have their pets tagged for identification purposes
• Passive RFIDs do not contain a power supply. Instead, the device is powered by radio energy transmitted by the reader. The antenna collects the energy from the transmitter to activate the chip. The range of a passive system is up to 1 metre, and some systems require the reader to be very close to the tag.
• Active RFID systems have a small battery within the tag, and the device will transmit its identifier at regular intervals. Depending on the power supply, the range can be up to 200 metres. Active RFID devices are commonplace in shops, where battery-powered tags are secured onto items. The tags are deactivated or removed when the goods are paid for. A reader is situated at the shop's exit and an alarm is triggered if it detects an active tag when a customer leaves the shop.