Passive tags are different than Active Tags in a few ways. Passive tags do NOT transmit. They “reflect” the readers energy with the tag data embedded within.
Think in terms of a mirror and a flashlight. If a person shines a flashlight at a mirror, the mirror reflects that energy back. That is exactly what a passive tag, also called a transponder, does. The key to passive systems is to have the tag pickup enough energy from the reader to actual send it far enough for the reader to hear the reflection.
Types of Passive RFID Tags
There are three primary frequency ranges used for passive RFID systems:
Low Frequency (LF)
125 KHz to 136 KHz
- Short Range Reading (contact – ~ 3”)
- Magnetic Coupling
- Applications include Access Control, Key FOBs, Animal Tracking
High Frequency (HF)
13.56 MHz
- Medium Range Reading (contact – ~ 10”)
- Magnetic Coupling
- Applications include Library Books, Access Control, DVDs, Payment Systems
Ultra-High Frequency (UHF)
860 – 960 MHz (902 to 928 in NA)
- Long Range Reading (contact – 50’)
- Far Field RF Coupling
- Applications include Inventory Systems, Access Control, Supply Chain, Toll Systems
