I am fairly new to the RFID world and have a project involving passive EPC Gen 2 UHF RFID tags. I’m not trying to track an asset’s location—I simply need to hit that tag with a read and then have it return a unique identifier. The challenge lies in the distance involved. I need to read tags from at least 50 feet away, and I need the reader to send out a fairly narrow directional scan. Imagine that I have a line of tags from left to right in front of a reader. Say there are 100 tags, 1 foot apart in a line. I need the reader to perform a directional scan that would only pick up a small subset of the tags. Would that be possible? Again, I don’t need any location data or anything else, just a single unique identifier that would be retrieved from the scan. If 50 feet were possible, would 100 feet be?
Most RFID readers cannot do directional scanning or read tags from a distance of 50 feet. Typically, a passive UHF reader can tell you that a tag is within the read field, which typically extends 20 to 30 feet from the reader antennal. However, there are a few companies that make phased-array antenna systems that provide a longer read range and can detect a tag’s location, typically to within about 10 feet. Mojix makes such a system. The company has separated the send and receive functions of the reader, so it places nodes that transmit energy to the tags in the areas where tags are located. The reader can be situated 300 or 400 feet away, and it can tell you the tag’s location to within 10 feet.
—Mark Roberti, Founder and Editor, RFID Journal
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