Are such readers available? If so, can you please recommend some companies that make them?
Most passive ultrahigh-frequency (UHF) readers employ RSSI, which stands for return signal strength indicator, and indicates the strength of the signal that the reader antenna receives from the tag. This helps to determine the tag’s distance from the reader, and can be used to determine the direction in which a tag is moving. Motorola Solutions‘ handheld readers, for example, utilize RSSI to create a Geiger counter-like function in which the readers beep more loudly as they get closer to a specific tag being searched for (the signal strength from the tag increases). Motorola’s fixed readers, as well as those from Impinj, CAEN RFID and other major manufacturers, also measure RSSI.
—Mark Roberti, Founder and Editor, RFID Journal
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