RFID Frequencies

Radio waves are the carriers of data between the reader and tags. The approach
generally adopted for RFID communication is to allocate frequencies depending on
application. The frequencies used cover a wide spectrum. These specified bands are:
Low Frequency (LF) 125 - 135 kHz
High Frequency (HF) 13.56 MHz
Ultra High Frequency (UHF) 400 -1200 MHz
Microwave 2.45 and 5.8 GHz
The allocation of frequencies is regulated by government agencies, requiring care in
considering RFID applications in different countries. Efforts at standardization should
avert these problems. The many varied applications will work their best at different
frequencies, therefore, it is important to understand the requirements before selecting
a particular type of RFID system. The most common uses of low frequency systems
are in security access, asset tracking and animal identification. They generally have
short reading ranges and lower system costs. High-frequency systems are used for
such applications as railroad car tracking and automated toll collection. They offer
long reading ranges and high reading speeds. This higher performance usually entails
higher costs. The power level of the interrogator and the power available within the tag
to respond will determine the reading range that can be achieved in an RFID system.
Like the restrictions on carrier frequencies there are legislative constraints on power
levels. Environmental conditions, particularly at the higher frequencies, can also
influence the range of communication.