Transponder with receiving means having a low electrical consumption in a listening mode

A transponder comprising:

• an antenna;
• and
• a receiver circuit to receive Amplitude Modulated RF signals (AM-RF signals), the receiver circuit comprising a wake-up circuit and further at least one demodulator, the receiver circuit being associated to a control mechanism of the transponder activating the receiver circuit at least periodically in a listening mode in which the wake-up circuit analyzes received RF signals and controls activation of the at least one demodulator in function of the received RF signals,
• wherein the wake-up circuit receives as entry an alternating signal branched from a signal chain through the receiver circuit upstream from said demodulator and having a carrier frequency of the received RF signals,
• wherein the wake-up circuit comprises a frequency discriminator arranged to detect when said carrier frequency is within a given frequency range,
• wherein the wake-up circuit further comprises a field clock generator and a digital modulation or preamble detector downstream from the field clock generator,
• wherein said digital modulation or preamble detector is formed by a clock-gap-clock detecting circuit including an evaluation circuit arranged to detect in a signal provided by the field clock generator the presence of gaps which have at least a predefined minimum time, and
• wherein the wake-up circuit is arranged to activate at least the demodulator to perform demodulation of the received RF signal only when said carrier frequency of a received RF signal detected by the frequency discriminator is within a given frequency range and a modulation or a preamble is detected in the received RF signal by the digital modulation or preamble detector, the wake-up circuit comprising an AND logic element receiving from the frequency discriminator a first logic signal and from the digital modulation or preamble detector a second logic signal, the first logic signal defining if the carrier frequency is within the given frequency range, the second logic signal defining if gaps having at least the predefined minimum time are detected in the signal provided by the field clock generator, and the AND logic element outputting a control signal provided to the wake-up circuit and enabling the activation of at least said demodulator only if the first and second logic signals have both a High state.