RFID systems are categorized by operating modes as either Passive or Active.
- Passive RFID transponders will not broadcast any radio signals unless they are triggered by an RFID reader’s electromagnetic field. Depending on desired reading distance and required performance in challenging environments, they operate in Low Frequency (LF), High Frequency (HF) and Ultra High Frequency (UHF) bands. Each frequency band has its own standard and communication protocol. UHF RFID technology is now widely used for asset tracking.
- Active RFID transponders does not require a reader for triggering since they have battery and can continuously broadcast their own signals. Although there are no globally recognized standards and protocols, they usually operate in two unlicensed frequencies, i.e. 433MHz and the microwave 2.54GHz band.
Each RFID system has its advantages and disadvantages relative to its capabilities, cost and need to be compliant with country specific frequencies, operating modes and communication protocols, which add complexity to selecting the optimum configuration for a specific application.