In an RFID device, how does the reader send data to interrogate the tag and how does the tag respond with the data stored in it ?

closed as too broad by uint128_t, PeterJ, Autistic, DoxyLover, Daniel Grillo May 8 '16 at 18:35

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  • Use RFID as a search term on the web and you will find volumes of info, more than we can print here. It gets elaborate, so we can only offer a basic description at best. – Sparky256 May 7 '16 at 22:16
  • You cannot get the ISO-18000 documents without paying for them, but the EPC Gen2 specification will describe the protocols. You can also look for the tutorial slide links from the IEEE RFID conferences; there's usually an intro to RFID that is technical but tractable. – b degnan May 8 '16 at 13:33

You need to research about how RFID works.

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Photo 1. Inside of an RFID card showing the loop antenna and chip.

The RFID reader emits a radio wave. The wire loop antenna in in the card picks up enough power (when close to the transmitter) to power the chip. which is also visible in your photo.

The chip modifies the radio signal in a way that the transmitter can sense and encodes the ID back to the reader as a modulated binary data stream. The reader demodulates the signal to extract the data which is then handled like any other digital data.

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