Patent ID: 8258928

Claim:
An RFID system, comprising: an RFID tag, comprising: an emitting module; a temperature detecting circuit, producing a time signal according to a surrounding temperature; and a tag chip, electrically connected to the temperature detecting circuit and the emitting module, wherein the time signal is transmitted via the emitting module; and a reader, comprising: a reader antenna, receiving the time signal; a transforming circuit, receiving the time signal from the reader antenna, and transforming the time signal into a temperature signal; and a control circuit, electrically connected to the transforming circuit and the reader antenna, wherein the temperature detecting circuit comprises a temperature retardation unit, a reference unit and a comparison unit, the comparison unit is electrically connected to the temperature retardation unit and reference unit, the tag chip is electrically connected to the temperature retardation unit, the reference unit and the comparison unit, and when the tag chip sends a pulse signal into the temperature retardation unit and the reference unit, the temperature retardation unit generates a retardation signal according to the pulse signal, the reference unit generates a reference signal according to the pulse signal, and the comparison unit generates the time signal according to the retardation signal and the reference signal.