A loop that talks
An NFC antenna is a loop tuned to 13.56 MHz. It couples inductively with a reader, exchanging both power and data across a few centimetres, and it doubles as the matching network that presents the right impedance to the chip.
Because the loop does two jobs at once — energy transfer and communication — its geometry matters far more than it looks. Trace width, number of turns, and clearance all move the tuning point.
Tuning and matching
The antenna must resonate at 13.56 MHz with the chip's capacitance taken into account. Too far off and the read range collapses; a small trim capacitor or adjustable matching lets you pull the loop back onto frequency.
We measure, not guess: a network analyser reading of the loop impedance is the ground truth, and it is how we confirm the design survives the final enclosure and any nearby metal.
Living with metal and plastic
Enclosures detune antennas. Metal behind the loop shifts inductance, and even a thick plastic case changes the coupling distance. The antenna has to be designed for the final stack-up, not for an open bench.
The finish line is a loop that reads reliably through the product housing, with margin for manufacturing tolerance and temperature.
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