RFID and RTLS

RFID

RFID (Radio Frequency IDentification) systems are systems in which the identity of a tag is read by a reader or interrogator. This is accomplished when the tag is in the vicinity of the reader’s antenna. The reader transmits a radio signal which is picked up by the tag which responds by sending back its identity. Tags may be passive (no battery) or active (containing a battery) and typically range in size from millimetres to centimetres. Passive tags and smaller form-factor tags generally have short reading ranges (centimetres), but active tags may have much longer reading ranges (metres up to several tens of metres). Tags can also be writable allowing the system via the reader to store information in the tag.

Generally RFID tags operate at 13 MHz or in the 840–960 MHz bands (depending on local radio regulations applying in the country of operation). Tags may be very low cost, but readers are relatively high complexity and are correspondingly more expensive.

There are applications in which the use of RFID is perfectly adequate for the purpose of locating or positioning objects. Readers may be placed at strategic ‘pinch points’ throughout the region of interest. Whenever tags move through the pinch points the reader identifies the tag and a software application keeps track of the zone in which each tag is located. These systems are particularly advantageous when there are very large numbers of tags, but relatively few zones (pinch points).