Patent ID: 6891475

Claim:
Radio-frequency transponder ( 12 ) for contactless identification by means of a reader ( 10 ), including:, an antenna ( 24 ) an analogue circuit ( 25 ) that includes a capacitor ( 32 ), an AC-DC converter ( 34 ), a modulator ( 40 ) and a demodulator ( 38 ), a logic control circuit ( 26 ), and a memory ( 27 ) said transponder ( 12 ) being arranged such that: the antenna ( 24 ) and the capacitor ( 32 ) together form a resonating circuit, the antenna ( 24 ) receives a first signal (Tx) originating from said reader ( 10 ), reader being sinusoidal having a peak voltage (Tx max ) and is modulated and carries commands, and transmits a second signal (Rx) carrying a response to the commands, said converter ( 34 ) converts the first signal (Tx) into a rectified signal in order to power the transponder ( 12 ) characterized in that said analogue circuit ( 25 ) further includes two clock extractors, one a high level extractor ( 36 ), the other low a level extractor ( 35 ), arranged such that the high level extractor ( 36 ) processes the first signal (Tx) in order to extract therefrom a clock signal addressed to the demodulator ( 38 ) as long as the peak voltage of this signal (Tx) exceeds a first threshold value, and such that the low level extractor ( 35 ) defines a second threshold value, said extractors being arranged such that the clock signal is interrupted as soon as the peak voltage of the first signal drops below said first threshold value, characteristic of the high level extractor, and such that it is re-established as soon as said voltage exceeds said second threshold value, characteristic of the low level extractor.