That is a complex question, and the answer depends on whether you are talking about an active RFID system or a passive system.
Active systems involve either tags waking up and broadcasting their signal every few seconds or minutes, or a reader emitting a signal that activates the tag. The tags generally do not cause much interference, because they emit very little energy for very brief intervals. The reader activating them, however, might interfere with other devices operating at the same frequency. Before purchasing an active system, you would need to know the frequency being used to wake up the tags, and find out what other devices in your environment utilize that same frequency. In general, I have not heard that active systems cause many problems.
Passive systems generally cause more interference issues, as the reader must emit a greater amount of energy to power the tags, which lack their own power source. High-frequency (HF) and low-frequency (LF) tags operate at 13.56 MHz and 125 kHz or 134 kHz, respectively. Not many devices operate at these ranges, so interference is not usually a problem. Ultrahigh-frequency (UHF) tags operate in the 856 to 960 MHz range, which overlaps with older cordless phones and Wi-Fi systems, as well as other devices. The reader emits energy to power up the tag, and this can cause problems for any other devices using the same frequency band. You might need to shield the reader antennas to prevent them from interfering with other devices.
Passive tags, on the other hand, do not emit energy. They reflect back a very weak signal to the interrogator, so there is no issue with such tags causing interference.
—Mark Roberti, Editor, RFID Journal
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