Co je to RFID?

RFID je zkratka pro RadioFrekvenční Identifikaci. RFID systém slouží k identifikaci a lokalizaci:

  • Lidí (např. autorizace, přístup)
  • Objektů (logistika)
  • Míst (transportní systémy)
  • Transakcí (platební systémy)

 

RFID funguje podobně jako běžné čárové kódy, ale jako nástupce má oproti nim tyto výhody:

For a basic description and understanding of the structure of the EPC code it would be enough for us to focus on three parts, which are color-illustrated in the following figure by the grey color. Here it can be seen a comparison to a conventional bar code, which is in format GS1-128 for marking common products, and subsequently formed EPC code (96-bit tag).

It is evident that, the greater the power of the transmitter of RFID reader, the greater the distance from with you can reliably get information from the RFID tag. For different environments there are suitable different carrier frequencies – long waves (lower frequency) are usable in rugged area, because of its ability to “go around the corner” and shorter waves (high frequency) “reach further” for the same power. Certain wavelengths are strongly influenced by liquids, others by metals. It would be best, if there were possible to choose the carrier frequency quite freely for each RFID implementation, measured as a best for particular environment, and the power of the transmitter set up to suit our needs.

Distances between the reader and the tag (attenuation paths):

The easiest way to estimate the strength of received signal by the tag antenna is to imagine, that the reader transmits a signal in all directions with the same power density (requires an isotropic antenna). In fact, such antenna can’t be built and even if it did, it wouldn’t be used, since the wanted tags are placed in some predefined directions and the radiation outside these areas would be only wasting of the emitted energy. This antenna is an ideal model and is serves only for calculations.

Because of the different principles of work between different types of working frequency (LF, HF, UHF), the following calculations are only relevant for cases of the UHF tags usage.