To answer your question, I reached out to an engineer at Impinj, which manufactures passive ultrahigh-frequency (UHF) RFID chips based on the EPC Gen 2 air-interface protocol. According to the engineer, if the read field is large enough, then it is possible to interrogate tags moving that quickly. The reason the size of the read field is critical is that if a tag is powered up for only a split-second, there is insufficient time for it to reflect back a signal with its encoded ID. Exactly how long the tag remains within the read field depends on a variety of factors, such as the tag IC and reader used, the reader antenna’s distance from the tag and so forth.
—Mark Roberti, Founder and Editor, RFID Journal
Can Multiple RFID Tags Be Read in Succession? »