UHF-band RFID systems are attracting increasing attention from the logistics and distribution industries for their ability to read IC tags at distances of over 5 meters. In RFID applications in these industries, tags are often attached to cases and pallets in order to keep track of inventory entering and leaving warehouses or to group goods by shipping address on sorting conveyors. However, implementation of UHF-band RFID systems has often proved problematic on the factory floor because the long read range can lead to unwanted and unintentional tag-reading, resulting in inaccurate data collection.
Omron’s new technology for estimating the distance between readers and IC tags solves these problems. Although technologies that use tags’ signal strength or special transmission protocols to measure this distance already exist, each has certain limitations. Signal strength, for example, differs depending on the direction a tag is facing, which makes it unreliable as a basis for measurement. On the other hand, the use of special transmission protocols requires IC tags with complicated circuitry, thus increasing implementation costs and impeding further penetration of RFID systems.
Omron’s new technology bases distance calculations on the delay time of the electromagnetic waves used in communication between reader/writers (antennas) and IC tags. This enables highly accurate distance estimations for UHF-band EPC-compliant tags, which are currently the most widely used tags. Like sound, electromagnetic waves take longer to reach a target the further away it is. As a result, the time taken for waves to travel from an antenna to an IC tag and return again (‘delay time’) differs according to the distance between the two points. The direction a tag is facing has no affect on delay time and thus does not compromise the measurement accuracy.
With this new technology, customers will be able to solve problems that have previously plagued UHF-band RFID system implementation, by preventing unwanted reading of tags on goods stacked near gate-mounted readers and discriminating between tags in areas where goods are traveling on multiple conveyor belts.
Omron is currently developing a system for detecting IC tags within a prescribed area by coupling this new distance measurement technology with its existing scan antennas. By using a scan antenna to set lateral dimensions and this new technology to measure depth, the system will allow users to isolate and read only those tags in a clearly defined area – ideal for applications in cluttered and overcrowded factory floors. After conducting factory floor tests, Omron is planning for product release in FY2008.
1 According to internal survey.
2 The time taken for electromagnetic wave emitted from an antenna to reach an IC tag and then return to the antenna as reflected waves.
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