Would power output be an issue with passive RFID systems?
Power output is an issue with passive RFID systems, because passive tags get their energy from a reader antenna. If a reader antenna blasts out a lot of energy, the tags have more energy to respond. Regulators limit the output because blasting a lot of RF would affect other RF devices in the area. It is not an issue for active systems since active RFID readers do not, generally speaking, emit energy (they may, in some cases, to wake up a tag). With most active systems, the tag is set to beacon at certain intervals, and the antennas of several readers receive those signals. Software is used to pinpoint the location of the tag.
If you were to put an active tag at one end of a 10,000-foot pipe, it might be possible to read the tag without any special equipment. The signal would bounce off the walls and be directed down the pipe toward the antenna. If a standard active tag didn't work, you could boost the signal from the tag or use repeaters halfway down the tag to ensure that the tag reads were captured.
—Mark Roberti, Founder and Editor, RFID Journal
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