Power would be an issue - recall that the chips draw their power from the signal the antenna picks up, and the system as a whole probably doesn't have a lot of margin. So powering up the T's Mifare Classic chip is OK, but powering up two or three of them might not work very well.
Getting past that, it would also be a problem if more than one tried to transmit at a time. Low-power RF systems like these often use backscattering for chip-to-reader communication - they don't actually transmit a signal of their own, they wait for their turn to speak, the reader keeps transmitting CW, and the chip tweaks the antenna's circuit so it's a bit more or less reflective of the incoming signal. Both having extra loads in the form of other chips, or having multiple chips manipulating the antenna's impedance, could make that work very badly.
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branchandroot
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Date: 2010-06-30 09:53 pm (UTC)Getting past that, it would also be a problem if more than one tried to transmit at a time. Low-power RF systems like these often use backscattering for chip-to-reader communication - they don't actually transmit a signal of their own, they wait for their turn to speak, the reader keeps transmitting CW, and the chip tweaks the antenna's circuit so it's a bit more or less reflective of the incoming signal. Both having extra loads in the form of other chips, or having multiple chips manipulating the antenna's impedance, could make that work very badly.