Radio frequency identification, or RFID, systems use data encoded into special tags to track items, people and even animals. These tags respond to certain radio frequencies, transmitting the data encoded in their circuitry. This allows users to quickly access information about tagged subjects, either directly from the encoded data, or by cross-referencing identification information with a database. RFID systems generally fall into two types, active or passive, and each has advantages and disadvantages.
Passive RFID
Passive RFID tags contain a small circuit as well as an antenna. When the tag detects the proper frequency of radio wave, the wave's energy provides the device enough power to respond with the encoded information. These devices require no external power source, but the limited nature of their broadcast ability means that scanners can only read these tags from a short distance. These tags are cheap to produce, however, and suited for applications such as retail inventory, where scanners come into close proximity with the tagged items.
Active RFID
Active RFID tags are similar in design, but they also contain a battery. This allows them to broadcast a signal constantly, regardless of the presence of any scanner. These tags are best suited to applications requiring constant monitoring, or in areas where RFID tags serve as security devices. An active RFID tag, always broadcasting, indicates to observers when a tagged item moved from its usual location, and provides owners with an easy way to track thefts. Scientists use RFID tags with powerful transmitters to track endangered animals, giving them information about movement and behavior patterns.
Semi-passive RFID
Another type of RFID tag is the semi-passive tag. These are similar to active tags in that they contain a battery, but it only provides power to the tag in response to a signal of the proper frequency. This saves battery power, but allows these tags to work in warehouses or other settings that might preclude bringing scanners in close proximity to tagged items. Instead, a single pulse from a fixed RFID scanner triggers every tag in range, and the battery-boosted responses travels farther than passive RFID signals.
Bottom Line
Active RFID tags provide the most comprehensive tracking data, but the cost of such systems limits their use to applications where constant monitoring is necessary. Passive RFID tags, with their small size and cheap manufacturing costs, are suitable for almost any application. Semi-passive tags offer a good mix of economy and reliability, while offering more range and readability than passive tags alone.
Tags: RFID tags, Passive RFID, These tags, Active RFID, Active RFID tags