I can’t wrap my brain around how nfc just “holds data” but doesn’t need power to transmit data? Like how do ID cards use nfc?
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There are at least a couple of main ways to do it.
The easiest one to understand is where the tag takes energy from the radio signal emitted by the reader. It then uses that energy to send data back. The tag has an antenna to harvest the energy and enough capacitance/inductance to store it briefly. The reader is both supplying data and supplying RF power to the tag.
The more difficult one to understand is “inductive coupling”. Essentially, the reader and the tag create a circuit, much like a circuit that contains a transformer. Except this transformer has no iron core; it has an air gap that takes the place of the core. Since both the reader and the tag are part of the same circuit, they can pass data back and forth.
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