I would like to create a kit that uses ultrahigh-frequency (UHF) RFID to detect if a person is entering or exiting a room. I want to place two antennas next to each other, and then ascertain which antenna detects a tag earlier. Will this work?
Yes, this should work, provided the tag can be read consistently. The challenge is that the human body is mostly composed of water, which absorbs RF energy in the UHF spectrum. So a person's body can sometimes prevent tags from being consistently interrogated. But if a tag is read consistently, then a reader can be set up to report which antenna picked up that tag's signal first, which should indicate the direction in which the tag (and thus the person) is moving.
—Mark Roberti, Founder and Editor, RFID Journal