What are Passive RFID Tags?

Alan Rankin

Passive RFID tags are devices to record electronic information that can be interpreted by a device known as an RFID reader. RFID stands for radio frequency identification, and RFID tags can be attached to or implanted in any object or creature, including humans. An RFID reader can access the information in an RFID tag remotely from a distance of several yards or meters. Passive RFID tags are distinguished from active RFID tags in that they have no independent power source and must be activated by a reader. Passive RFID tags are widely used in various business, government, and transportation applications.

The United States uses passive RFID tags in passports.
The United States uses passive RFID tags in passports.

The technology behind RFID tags was pioneered in the 1940s by Russian scientist Leon Theremin, who created a passive, powerless device used for eavesdropping in Soviet espionage operations. Later, scientists explored the potential of the technology for benign uses, such as tracking and identifying aircraft. This device, called a transponder, is still used on aircraft in modern times. Advances in technology allowed for miniaturization of the devices, allowing for the creation of passive RFID tags that could be attached to objects as microchips, stickers, or even medical devices that can be surgically implanted.

Passive RFID tags record digital information that can be accessed with a RFID reader.
Passive RFID tags record digital information that can be accessed with a RFID reader.

Passive RFID tags include a small quantity of computer circuitry, an antenna for receiving and transmitting information, and sometimes a covering to protect or insulate this equipment. The circuitry and antenna can be so small as to be virtually undetectable, because the limited functioning of the device does not require a power supply or moving parts. When an RFID reader is used within range of the tag, it sends a signal that activates the tag’s antenna. The antenna then transmits the information contained in the circuitry to the RFID reader. The rest of the time the tag is dormant.

Passive RFID tags have gained widespread use in industry and government as a method of inventory control, superseding previous methods that required time-consuming input of product data. Implantable RFID chips have long been used in animals, first as livestock monitors for farms and later to track or identify runaway pets. In the 21st century, they are used for identification and payment in public transit, toll roads, and even credit-card transactions. Various governments and independent businesses have used them for property and personnel identification to prevent theft and control facility access. Starting in the 2000s, they were also added to various official documents, such as passports.

The widespread use of passive RFID tags has not been without controversy; in particular, privacy advocates fear RFID tags with personal information could be abused by officials or criminals. Some companies sell devices to block RFID signals, so the tags can only be activated with a person’s knowledge and consent. The U.S. Food and Drug Administration (FDA) approved implanted RFID chips for human use in 2004, with chip companies proposing they could contain medical records or eliminate the need for ID cards. Needless to say, this did not sit well with privacy advocates. The FDA acknowledges there may be possible complications from implanting the new technology, including allergic reactions, interference with medical devices, or even cancer.

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