RFID
Lets a reader exchange identification or other supported data with a compatible radio-frequency tag. Passive tags obtain operating energy from the reader's field, while active tags have their own power source. Frequency, protocol, identifier format and memory capacity depend on the selected system.
A compatible reader energizes or communicates with a tag, and receives the tag's response. Passive UHF systems can return information by changing the reflected signal, a technique called backscatter. Do not assume every RFID device uses the same frequency, coupling method, identifier length or security features.
In plain terms
Like a radar reflector cluster on a small boat — when a coast-guard radar pings, the cluster reflects back a signature; RFID just adds the ability to encode 'who I am' in that reflection.
Why designers use it
- Asset tracking — supply chain, retail, library, hospital — every box, book, and IV-bag tagged with a passive UHF inlay.
- Access control — HID Prox cards, MIFARE building badges, hotel room cards.
- Anti-counterfeit — pharmaceutical and luxury-goods authentication via embedded RFID chips.
- Battery-free wireless ID — passive tags last decades; the tag itself can outlive the product it labels.
Best for
- Supply chain
- Access control
- Inventory
Key specifications
- Operating limits: Check the exact manufacturer's datasheet (A family name does not establish voltage, current, temperature or timing limits.)
- Pin assignment: Match the complete part and package code (A similar name or function does not guarantee the same wiring.)
- Mechanical fit: Use the exact package drawing (Check pad layout, dimensions and viewing direction before building.)
When not to use it
- Through metal or water without compensation — UHF doesn't penetrate metallic packaging; pull on-metal-rated tags or LF/HF.
- When precise location is needed (>1 m granularity) — pull UWB or BLE+anchors.
Common mistakes
- Stacking RFID tags on top of each other — antennas detune and read range collapses.
- Ignoring polarisation between reader and tag antennas — circular vs. linear pol mismatch costs 3–10 dB of read range.
Where you will find it
- A Walmart pallet of consumer goods carries Impinj M775 EPC Gen2 UHF RFID tags on each carton: when the pallet enters the store's loading dock, an Impinj R420 reader inventories all 3,000 tags in 4 seconds, populating the store's inventory system with no manual scanning.
- A New York City MTA OMNY contactless payment system uses HID iCLASS SE LF/HF readers at every subway turnstile reading commuters' MIFARE-branded tap cards or NFC-enabled phones: each tap takes <300 ms, processing 5 million rides per day.
- A medical-device anti-counterfeit RFID tag from NXP NTAG 213 on a Pfizer vaccine vial provides authentication by NFC: a pharmacist's phone reads the tag and verifies the encrypted serial against Pfizer's database, defeating fake vials in unregulated markets.
A short history
RFID Journal's historical account describes several separate developments in identification, access control and tracking. It attributes the claim of a first US active-tag patent to Mario Cardullo rather than presenting that priority as independently settled. Its Los Alamos example explains passive UHF operation through energy harvested from the reader and a modulated reflected response called backscatter.