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Alien Software Adds Context to Tag Reads

A free firmware upgrade will enable owners of Alien fixed readers to determine the direction, distance and speed of an EPC Gen 2 UHF passive tag.
By Mary Catherine O'Connor
Jun 23, 2008Alien Technology announced today that its Intelligent Tag Radar, which enables users to determine the direction, distance and speed of an EPC Gen 2 UHF passive tag, will be available beginning June 30. The software also allows an Alien interrogator to singulate a tag in close proximity to other tags. Alien Technology previewed this software at the RFID Journal LIVE! 2008 conference in April of this year.

"People are moving out of pilot projects [using RFID] and toward real installations," says Scot Stelter, Alien Technology's director of reader product marketing. "One thing Alien wants to do to help that process is to make RFID more effective, by providing actionable information that goes beyond the tag ID number."

The software works by analyzing the data it collects during each read event—that is, every time a tag is detected within the reader's interrogation zone. To singulate each tag—in other words, to identify one tag within a group of tags in close proximity to one another—Alien's ITR software locates the "top dead center," or highest point of the frequency wavelength, of each tag's signal in relation to the antenna, in order to determine when the tag is directly in front of that antenna. This technique is similar to how radar systems locate airplanes, Stelter explains.

The level of accuracy of the singulation function directly correlates with the number of tags within a reader's interrogation zone, as well as the tags' distance from the reader antenna. According to Stelter, it will work best for singulating tagged items moving down a conveyor belt, wherein the reader antenna is mounted next to the passing items. In this scenario, he says, tagged items spaced just a couple of centimeters apart can be singulated. Having more items farther from the reader makes singulation more challenging.

Additionally, the software can determine a tag's velocity, or speed in motion, enabling a user to discriminate between stationary and moving tagged objects. To measure velocity, the user must attach two antennas to the reader running the ITR software. A tag is singulated by each antenna as it passes by, indicating that tag's direction (i.e., whether the tag is moving right to left, or left to right), and as well as its speed.

According to Stelter, this feature can be employed to automate decision-making based on tag speed and location, which could prove useful in some asset-tracking applications. The ITR software can determine the speed of a single tag within a reader's interrogation zone at up to 50 miles per hour. It can track the speeds of multiple tags in its interrogation zone, though the software can measure velocity only up to 30 times per second. Tracking the speed and direction of 30 tags within an interrogation zone, therefore, provides that data once per second.

To determine a tag's distance from a reader, the ITR software uses an algorithm that counts the wavelengths of a tag's response to interrogation. The distance of any tag within a reader's interrogation zone can be determined, Stelter says, with an error margin of 10 percent. (If a tag is 10 feet from the reader, for example, the software may come up with a calculated distance of 9 or 11 feet, instead).

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