The area in which a passive interrogator can provide enough energy to power up a passive tag and receive back information. Also called the read field or reader field. Tags outside the interrogation zone do not receive enough energy from the interrogator to reflect back a signal.
Interrogator - A device used to communicate with RFID tags. The reader has one or more antennas, which emit radio waves and receive signals back from the tag. The reader is also sometimes called an interrogator because it "interrogates" the tag.