Classification by frequency:

Low Frequency (LF) technology typically operates in the 125-134kHz⁽¹⁾ part of the frequency spectrum. While its range is very low (few centimetres) and its bandwidth is relatively low, it is almost immune from nearby metals and liquids, and is often used for animal tagging, car immobilizers (a tag is embedded in the keyfob) and contactless cards (staff badges). It usually lacks anticollision features.

High Frequency (HF) is probably the most widespread RFID technolology at the moment. It uses the 13.56MHz⁽²⁾ part of the spectrum (which is available worldwide) and offer a medium range (up to 1.5 meters, depending on the relative size of the tag's and reader's antenna) and medium to high transfer rates.

The most common uses for this techology are smart labels, smart cards (like the Oyster card) and the Near Field Communication (NFC) phones.

Ultra High Frequency (UHF) uses the 865-868MHz⁽⁴⁾ band. While this is not standardized worldwide (US uses 902-928MHz), there are wideband tags compatible with both the frequencies. It features long reading ranges (in the order of meters), high reading speed and it is able to read hundred of tag IDs at the same time.

This is the standard esperiencing the biggest growt, and its Gen2 implementation has been adopted by major players as Wal-Mart and the US Depatment of Defence, while another UHF technology (EM4122) is in use for itel-level stock control in Mark&Spencer's stores.

Part of this technology uses the 433MHz⁽³⁾ band, mainly used for active tags tags like the Wavetrend (also, most of the domestic wireless equipment such as remote temperature sensors and car remotes are operating at this frequency as well).

Microwave (MW) uses the same frequencies licensed for WiFi (2.4GHz⁽⁵⁾ and 5GHz⁽⁶⁾). In this range of frequency, passive power transmission is not particularly efficient and the range is limited, so this frequencies are used mainly for active tags for RTLS (eg. the Ekahau device) or for toll collection (eg M6 Toll Tag and TelePass), with the notable exception of the Hitachi µ-tag.

Electromagnetic Spectrum

Classification by the way the tag is powered:

Passive RFID: this is probably the most common form, mainly due to its extremely low cost and reduced dimensions. The RIFD tag gathers the power from the reader, via inductive coupling (LF and HF) or backscattering (UHF). While this has innegables advantages in term of cost, it has the drawback of the reduced range from the transmitting antenna - usually between few centimeters (HF) to few meters (UHF). Typical examples are Gen2 tags, PJM tags and MIFARE.

Active RFID: this is reserved to more expensive applications, where range and accuracy are of primary concern. The tag is powered with a battery, and the range can be extended at will. Most batteries are not rechargeable or replaceable, so active tags have a limited lifespan (usually years). A typical example is the Wavetrend tag, but every battery power device with wireless capabilities (laptop with WiFi, mobile phone) can be considered part of this category.

Battery assisted passive RFID (BAP): this technology tries to get the best of the two worlds. The tag contains a battery, but this is used only to power the chip, and not for signal transmission (the signal is still backscattered to the reader as in the case of the passive tag). The performances and the cost are in the middle between passive and active tags - usually with a range between 20 and 100 meters. Typical example are the PowerID tag and Intelleflex technology.

WM RFID Centre

RFID technologies

Classification by frequency:

Classification by the way the tag is powered: