NFC terminal
Near field communication( NFC) works contactless between the NFC terminal and the NFC tag. A distinction is made between active and passive tags. Active tags have a rechargeable battery, whereas passive tags draw their energy from the high- frequency electromagnetic field of the NFC terminal, which is established between the two components by the NFC reader for reading the data from the NFC tag.
The passive NFC tag, which is brought within 10 cm of the NFC terminal and thus of the alternating field, receives the carrier signal from the NFC reader and derives a voltage from it, which is used to charge the battery of the passive and semi-passive tags. This voltage forms the supply voltage for the microprocessor. The signal transmissionfrom the NFC tag takes place through a kind of load modulation of the RF field from the NFC reader, in which the microprocessor switches components on and off and thus influences the alternating field.
As for the NFC terminal, it can be a standalone NFC reader or a smartphone equipped with an NFC chip. Almost all smartphone operating systems support near-field communication, which is contactless in duplex, half-duplex or sequential between the NFC reader and the NFC component. ISO/ IEC have specified the physical and data characteristics of the transmission link between the NFC reader and the NFC components in various standards. For example, ISO 18092 specifies the transmission standard and ISO 14443 specifies the physical and data properties of the transmission link between the NFC device and the NFC reader.