The Defense Department initially implemented active RFID for inventory control back in the early 1990s, after the first Persian Gulf War. Before that, military supply requisitions were placed either on paper or through EDI (electronic data interchange), often resulting in lost or incorrectly filled orders, said Bruce Jacquemard, executive vice president and general manager of global field operations for Savi Technology, a builder of RFID networks.
The Defense Department currently uses Savis active RFID technology to track cargo shipments in 46 countries worldwide. Meanwhile, U.S. allies such as the United Kingdom and Denmark have started deploying Savis products in their own supply chains, Jacquemard said in an interview.
Savi has also begun working with the Defense Department on new "hybrid" applications that combine active and passive RFID technologies, according to Jacquemard.
In the Defense Department tests, Savi is capturing information stored in passive RFID tags, attached to contents of shipping containers, and then integrating this data into RFID tags attached to the containers.
How do these two wireless tracking technologies compare? Essentially, active and passive RFID both use RF (radio frequency) energy for communicating between a tag and a reader device, or scanner. But the methods for powering the tags are not the same. Active RFID uses a battery within the tag; passive RFID depends on RF energy transferred from the reader to power the tag.
Although active RFID is more expensive than passive RFID, its a technology that allows RFID tags to be continuously powered, and to generate high-level signals back to the reader, even with only low-level signals from the tag, advocates say.
These distinctions translate into differences in communications range, the ability to collect information from multiple tags, functionality in metallic and wet environments, and opportunities to integrate with other sensor technologies.
"Generally speaking, passive RFID can only transmit over a range of about 300 feet," said Allan Griebenow, CEO of Axcess International Inc., an RFID systems provider.