What are the frequencies used in RFID?

RFID systems use different work frequencies, classified as:
- Low frequencies (LF, between 125 and 134 kHz)
- High frequencies (HF, around 15 MHz)
- Very high frequencies (UHF, 860 and 960 MHz)
- Micro-wave (superior than 2.45 GHz)
Each frequency has different features and therefore is suitable for different applications. Briefly, the frequency growth increases both the reading distance and the amount of information transferred in time unit, diminishing the resistance capacities to operating conditions and costs. The low-frequency tags use little power and are enable to cross non-metallic materials and liquids, but the signal for reading does not extend 30-90 centimeters. The high-frequency tags work better with metal objects and manage to cover more than a meter of distance. The highest frequencies offer more extensive reading range, and allow faster data transferring, although cannot easily surpass through materials.