How is data stored in a rfid tag?

Question

i mean what is the data structure of a tag

Answer 1

simple. a chip (IC or integraded circuit)

BUT if you wanting to know how its read from the RFID reader...

The tag is known as a passive transmitter.(it doesnt contain power)

The tag has a coil of wire inside known as an inductor which acts as an arial. The ID tag is powerless untill it is close to the reader, which activates the tag through magnetic radiation(radio waves). The ID tag then transmits all its data thats stored in its chip.

Answer 2

More specifically, there is always a ROM chip of some sort on the RFID IC (Integrated Circuit) that holds the storage.  The data is conveyed from the ROM, through the IC, and through the tiny antenna to the reader.

The data structure varies based type and application.  Tags vary in size (64Bit, 96 Bit, etc).  The data usually consists of fields such as tag type, header, filter value, company ID, asset type, serial number, asset reference, etc.

There are some IEEE standards in the works, but as far as I know, nothing is in place.  http://www.rfidjournal.com/blog/entry/39...