Is it usually four ports?
The maximum is eight, though four is more common—but you have to check whether the ports are monostatic or bistatic. Bistatic readers have separate send and receive antennas, so while you would have eight ports, four would be emitting energy to power up passive ultrahigh-frequency (UHF) tags and four would be receiving data from the tag. They have the same coverage as a four-port monostatic reader, which combines the send and receive functions onto a single antenna. Keep in mind that bistatic antennas generally perform better, since you don't have to shut down emissions and then listen for a signal back.
—Mark Roberti, Founder and Editor, RFID Journal
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