Warehouse Management Systems (RFID)

Two main types of RFID tags

Passive RFID Tags

Passive RFID tags have no internal power supply. The minute electrical current induced in theantenna by the incoming radio frequency signal provides just enough power for the CMOS integrated circuit in the tag to power up and transmit a response. The lack of an onboard power supply means that the device can be quite small: commercially available products exist that can be embedded in a sticker, or under the skin.


As of 2006, the smallest such devices measured 0.15 mm × 0.15 mm, and are thinner than a sheet of paper (7.5 micrometers). Passive tags have practical read distances ranging from about 10 cm to up to a few meters depending on the chosen radio frequency and antenna design/size. Due to their simplicity in design they are also suitable for manufacture with a printing process for the antennas.Non-silicon tags made from polymer semiconductors are currently being developed by several companies globally.

If successfully commercialized, polymer tags will be roll printable, like a magazine, and much less expensive than silicon-based tags. The end game for most item level tagging over the next few decades may be that RFID tags will be wholly printed - the same way a barcode is today - and be virtually free, like a barcode. However, substantial technical and economic hurdles must be surmounted to accomplish such an end: hundreds of billions of dollars have been invested over the last three decades in silicon processing, resulting in a per-feature cost which is actually less than that of conventional printing.


In 2007, the Danish Company RFIDsec developed a passive RFID with privacy enhancing technologies built-in including built-in firewall access controls, communication encryption and a silent mode ensuring that the consumer at point of sales can get exclusive control of the key to control the RFID. The RFID will not respond unless the consumer authorizes it, the consumer can validate presence of a specific RFID without leaking identifiers and therefore the consumer can make use of the RFID without being trackable or otherwise leak information that represents a threat to consumer privacy.




Active RFID Tags

Unlike passive RFID tags, active RFID tags have their own internal power source which is used to power any ICs that generate the outgoing signal. Active tags are typically much more reliable (e.g. fewer errors) than passive tags due to the ability for active tags to conduct a "session" with a reader.


Active tags, due to their onboard power supply, also transmit at higher power levels than passive tags, allowing them to be more effective in "RF challenged" environments like water (including humans/cattle, which are mostly water), metal (shipping containers, vehicles), or at longer distances.

Many active tags today have practical ranges of hundreds of meters, and a battery life of up to 10 years. Some active RFID tags include sensors such as temperature logging which have been used to monitor the temperature of perishable goods like fresh produce or certain pharmaceutical products.

Other sensors that have been married with active RFID include humidity, shock/vibration, light, radiation, temperature, and atmospherics like ethylene. Active tags typically have much longer range (approximately 500 m/1500 feet) and larger memories than passive tags, as well as the ability to store additional information sent by the transceiver.