on the contrary most tag antennas I've seen (e.g. from inlays or transparent tag-stickers) use antennas with a lot more windings. Thinking in the "air transformer model" this means, that they get higher voltages on the "secondary" coil (=tag). This sounds reasonable, since it is easier to decode a signal (reader sends ASK in ISO14/15K modes) with clear voltage readings.
But maybe I get this wrong. Can someone explain my observation ?
Basically I can tune any antenna-coil to the 13.56 mhz with a parallel or series capacitor - it's just, that the needed capacitance may get unhandy, when to big or to small - and that I get different bandwidths (= Q-Factor) out of such a (R)LC System. Am I right ?
One last question:
Most descriptions of the backscatter system I've seen use the transformer model: When the tag draws more current from the secondary (=tag) coil (for example by shortening the coil with an transistor), the current on the primary (=reader) coil also increases which also increases the voltage drop on the reader side.
on the contrary there seem to be a second effect: by shortening the coil on the tag, the LC-System is detuned - which leads to less energy transfer from the primary coil. worse tuning means less currents means less voltage drop on the reader side.
how do these both effects match ?
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