Passive RFID
Radio frequency identification technology where tags have no power source and only respond when energized by reader signals. Much cheaper than active RFID but with limited range (typically centimeters to a few meters). Used for inventory management, access control, and zone detection at doorways or choke points. Not suitable for real-time tracking but excellent for item-level identification.
Radio-frequency identification technology where tags have no battery, powered by electromagnetic energy from reader, responding with stored identification data. Passive RFID operates at multiple frequencies: LF (125-134 KHz, 10-30 cm read range), HF (13.56 MHz, 10-100 cm range, ISO 15693 standard), UHF (860-960 MHz, 1-12 meter range, EPC Gen2 standard). Passive RFID advantages: (1) Low tag cost - $0.05-$3 per tag, much cheaper than active RTLS tags ($25-150). (2) No battery maintenance - tags last indefinitely. (3) Small form factor - tags can be tiny labels, non-intrusive. (4) Mature technology - extensive vendor ecosystem, standardization, proven reliability. Passive RFID limitations for RTLS: (1) No continuous tracking - tags detected only when near reader versus active RTLS providing constant position updates. (2) No precise positioning - zone-level only, not coordinates. (3) Limited range - UHF maximum 12 meters (often 3-6 meters practical), requiring many readers for facility coverage. (4) Read reliability challenges - metal and liquids interfere with RF propagation, affecting detection rates (may miss 10-30% of tags in challenging environments). (5) Collision issues - many tags in reader field simultaneously can cause read failures though Gen2 protocols handle 100+ tags. (6) Orientation sensitivity - tag-reader orientation affects read success.
Passive RFID infrastructure costs: fixed readers $500-3000 per location, handheld readers $1000-4000, antennas $100-500. UHF readers typically support 4 antennas covering multiple read zones. Total system cost dominated by reader/antenna infrastructure versus inexpensive tags.
Passive RFID standards: EPC Gen2 (UHF), ISO 15693 (HF), ISO 14223 (LF), ensuring multi-vendor interoperability.