Antennas for NFC Devices
Antennas appear in any device or tag that provides Near Field Communication (NFC) support because you need an antenna to transmit the RF energy. Think of the antenna as a sort of speaker for your radio. You couldn’t hear the music without a speaker; likewise, NFC cannot send a signal without an antenna. Of course, the antenna also receives signals, much the same as your ears receive sound from the radio.
Every NFC device requires an antenna. You can’t send and receive data without one. The figure shows a typical antenna for a tag. In general, the antennas all look similar because they provide the same functionality no matter what sort of device you use.
The antenna attaches to some sort of chip or Integrated Circuit (IC). For the tag shown, the chip is relatively simple — a smartphone would have more hardware associated with the antenna. The chip provides any memory, intelligence, and programming the tag requires.
Of course, you need something to hold everything together. The antenna wires won’t tolerate much abuse, so the tag relies on an inlay to ensure that the tag remains functional. Don’t get the idea that the inlay is always a simple piece of plastic (this is true for a dry inlay only). The inlay construction and materials vary according to the purpose of the tag. For example, an on-metal sticker has six layers of material that include a ferrite foil barrier to keep the metal used to hold the tag from interacting with the antenna. You can see a number of inlay types here.