Can you hear me now? Spectrum-enabled RFID tags store and share data

CHIPS, Summer, 2004

Even if you have never heard of Radio Frequency Identification (RFID), you probably recognize the names Wal-Mart and Target. Both retail giants made big technology news last year. In November 2003, Wal-Mart defined a requirement for its largest suppliers to tag all cartons and pallets with wireless RFID sensors by Jan. 1, 2005. Target followed suit in February 2004, requiring some suppliers to use RFID tags on each case and pallet shipped by mid 2005.

RFID, a wireless spectrum technology that has existed for over 50 years and has been used by the Department of Defense (DoD) since World War II, has made it big in the commercial retail market. Although the commercial use of RFID made the news, the RFID trendsetter role can still be claimed by DoD and in particular by the Department of the Navy (DON).

Oct. 2, 2003, DoD issued a policy memorandum directing the immediate use of high-data capacity, active RFID technology that will affect all companies supplying goods to the DoD. But even earlier, during May 2003, the U.S. Navy Bureau of Medicine and Surgery implemented a Tactical Medical Coordination System.

Using versatile RFID technology, this custom-developed system simplifies hospital administration, reduces medical practice errors, provides better medical care, tracks common injuries and analyzes long-term trends by transferring patient information stored on RFID tags. Linking to a wireless local area network, unique data are exchanged, further eliminating manual reentry at a computer workstation.

While high cost components deserve the supply chain tracking benefit of RFID, it is notable that the DON found among its first applications, a solution to care for its most valued assets: Sailors and Marines.

Each patient admitted into Navy Fleet Hospital Three in Iraq is tagged with an RFID-enabled wristband. U.S. military personnel and other patients, including prisoners of war and the indigenous populace, are tracked by unique ID numbers embedded in the RFID tags. Medical staffs use RFID readers to scan the bracelet to confirm identity and enter information on diagnoses and treatments.

Turning from the humane to the mundane, during FY 2004, DoD will acquire more than $24 billion worth of supplies (beans, bullets, bandages) and services to support America's fighting forces, and that tangible supply chain will translate into a lot of logistics-related RFID tags.

How does an RFID system work?

A basic RFID solution is comprised of a minimum of three components--a radio frequency tag, which is actually a microchip that is an electronically programmed transponder containing unique information, an antenna device and a transceiver to communicate and decode the stored information.

When the transceiver sends out its electromagnetic waves, they form a magnetic field which "excites" the antenna on the RFID tag. A passive RFID tag accepts the magnetic field and powers the microchip's circuits. The chip then modulates the waves that the tag sends back to the reader and the reader converts the new waves into digital data.

The recent activity within the RFID industry will definitely improve the cost of components, but for the benefit of this discussion we need some baseline understanding. Passive paper tags, probably the least expensive tag in use, may be available for less than 20 cents, and hardened active tags on reusable containers are available for approximately $20. Transceivers are roughly $1,000 each.

There are several spectrum bands associated with RFID use (see Table). Spectrum for RFID technology has not yet achieved harmonized international regulations, so use of specific spectrum bands associated with RFID is still a regulatory issue for each administration. Lacking a single standard, organizations could receive product tags for various spectrum bands requiring a transceiver in each of those bands to capture the tag data. In a normal operating environment, the result can be many tags and a number of frequency compatible transceivers.

Since RFID is based on proximity, unlike bar codes and their line-of-sight associated readers, the transceiver can process and analyze all of the "packages" as an entire pallet transits a loading dock. The time savings by not requiring visual contact with the tag are significant.

Tag Types: Passive, Active, Semi-passive

In the commercial implementation it is likely that passive RFID devices will be the norm. However, DoD's current policy anticipates supporting both active and passive devices. Passive RFID tags weigh less than active tags, are less expensive, and their operational lifetime is not dependent upon battery life. But they have shorter read ranges, more limited data storage than active tags and require a higher-powered reader.

Active RFID tags come with a battery and transmit a signal to a reader. Active tags can be read from 100 feet or more away, but at present they are significantly more expensive than their passive sibling. They are used for tracking expensive items over long ranges. Currently, the U.S. military uses active tags to track containers of supplies arriving in ports.