NFC technology NFC RFID tag Dealer

　　NFC (Near Field Wireless Communication Technology) evolved from RFID technology. Its carrier frequency band is 13.56MHz and the wavelength is about 20 meters, which belongs to the short wave band.

　　We know that the size of the antenna used for radio transmission should be close to the wavelength of the radio wave in order to obtain the ideal electromagnetic energy radiation performance, and the short-wave band where NFC is located, if it is to effectively radiate electromagnetic energy, the antenna size will be larger— —Refer to the whip antenna on the radio that accepts shortwave broadcasting. However, NFC does not have such an antenna.

　　What is the principle of NFC technology?

　　The principle of NFC near-field wireless communication technology focuses on "near-field", which uses the mutual coupling of inductance, and the basic principle is equivalent to a transformer. If the subject has removed some RFID magnetic cards, you will find that there is a coil inside, which is actually the secondary coil of the inductor.

　　NFC evolved from RFID technology. The principle of RFID is as follows: RFID card and reader each have an inductive coil. When we put the RFID card close to the corresponding reader, the inductive coupling coil inside the reader It acts as the primary coil of the transformer and supplies power to the passive RFID identification card. At this time, the inductive coil on the RFID card is equivalent to the secondary coil of the transformer. On the other hand, the chip in the RFID card modulates the information stored in it On the coil of the RFID card (the modulation principle is to regularly change the impedance of the coil to regularly change the load of the inductor primary coil), the RFID reader can detect the change of the impedance of the inductor The information in the card is read out.

　　This is why RFID technology can only be used for short-range recognition and card reading-the distance between the two coils of the mutual inductor cannot be too far, otherwise the energy will quickly decay to zero.

　　As an upgraded technology of RFID, the principle of NFC is essentially the same, but its function has been greatly enhanced. In NFC technology, the two coils of the mutual inductance can both be active coils, such as two mobile phones. At this time, the two active NFC coils close to each other are only responsible for the communication function and no longer need to supply power to the other party. The communication rate has been greatly improved-up to several hundred bps.

　　We often see publicity saying that RFID or NFC is used for positioning technology. In fact, the principle of RFID or NFC positioning is completely different from the well-known wireless positioning technologies such as GPS. The principle of RFID for positioning is still "process wireless communication". Since it can only be identified at a short distance, it can also be used for positioning-once an RFID card is identified at a certain point, the card must be located near the reader. Therefore, RFID positioning technology is often used in industrial production lines, logistics and other industries

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