NFC antenna design and online calculator
NFC antennas operate at low frequency (13.56Mhz) on small devices, usually a smartphone. An NFC antenna is not an antenna at all, it is really just a big inductor. Depending on the antenna size in the device, NFC antennas are often simply loops of wire, occupying as much area as the device allows.
Depending on the antenna size, the number of turns has to be chosed in a way to achieve an antenna inductance between 300nH and 3 uH
The parasitic capacitance should be kept as low as possible to achieve a self-resonance frequency >35MHz. A typical the number of turns will be in the range N=1-6, which is suitable for various applications and antenna sizes.
The inductance can be estimated using the following formula:
The inductance can be calculated by:
D Average antenna diameter
s Antenna width
N Number of turns
| Number of turns N | ||
| Diameter D | ||
| Antenna width s | ||
| Antenna inductance L | ||