Yes. Reader systems that can detect the positions and movements of passive ultrahigh-frequency (UHF) transponders use phased-array antennas. These antennas have multiple antenna elements within a single unit, and are able to create read fields in different directions and with different sizes and shapes. If a tag is excited by a particular read field but not others, you can determine the direction in which that tag is moving. Using received signal strength, you can also ascertain the tag's distance from the reader, though this cannot be accomplished with great precision. Still, these antennas can tell you that a tag is on or near a specific shelving unit or rounder within a retail store—which is often all you need to know.
Checkpoint Systems offers its Overhead 2.0 reader (see RFID News Roundup: Checkpoint Systems Enhances RFID-Based Overhead EAS Solution). Mojix has its STAR 3000 reader system (see Mojix Announces the Availability of Its Next-Generation RFID System). And Sekura offers the Vertic RFID Overhead System. We recently published a feature covering these products (see What You Need to Know About Overhead RFID Readers).
—Mark Roberti, Founder and Editor, RFID Journal