Abstract: A contactless chip card includes a circuit for detecting the presence of radio frequency signals. A detector comprises at least one circuit for detecting the presence of radio signals by making direct use of the corresponding signals received by an antenna winding. In addition, a phase-shift detector detects the relative phase differences between signals provided by the antenna winding.

Abstract: A contactless chip card, receiving binary data transmitted by radio frequency, includes a demodulator for the binary data. The demodulator includes a circuit for the detection of the transmitted signals, a rectifier circuit, a bandpass filter, two comparators and a memory circuit. The bandpass filter provides a low-frequency signal used as a reference for the two comparators and a high-frequency signal that is compared with the references varying with the low frequency signal. As a result, the demodulation is independent of the mean level of the received signal.