How NFC works

NFC is a short-range, high-frequency radio technology. The NFCIP-1 standard stipulates that the communication distance of NFC is less than 10 cm, the operating frequency is 13.56MHz, and the transmission speed can be 106Kbit/s, 212Kbit/s or 424Kbit/s.  NFCIP-1 specifies in detail the transmission speed, encoding and decoding methods, modulation scheme, and frame format of the RF interface of NFC devices. This standard also defines the transmission protocol of NFC, including the start-up protocol and data exchange method.  

NFC operating modes are classified into passive mode and active mode.  In passive mode, the NFC initiating device (also known as the master device) needs a power supply device. The master device uses the power supply device's energy to provide the RF field and send data to the NFC target device (also known as the slave device) at a transmission rate of 106kbps, 212kbps or 424kbps.  The slave device does not produce radio frequency field, so can not need power supply equipment, but the use of the master device generated by the radio frequency field into electricity, power for the slave device circuit, receive the data sent by the master device, and the use of load modulation (load modulation) technology, the data from the slave device back to the master device at the same speed.  This mode is called passive mode because the slave device does not generate the RF field, but passively receives the RF field generated by the master device. In this mode, the NFC master device can detect the contactless card or NFC target device and establish a connection with it.  

In active mode, both the initiating device and the target device must actively generate the RF field when sending data to each other, so it is called active mode. Both devices need power supply to provide the energy to generate the RF field.  This communication mode is the standard mode for peer-to-peer network communication and can achieve very fast connection rates.