Abstract: A method and a circuit for detecting a modulation factor in a signal received in amplitude modulation, including comparing the received signal with two first values, comparing the received signal with two second values ranging between the first two values, and considering the presence of an insufficient modulation depth if the received signal ranges between at least two of said values.

Abstract: A system of contactless electromagnetic transmission between a terminal including a series oscillating circuit for generating an electromagnetic field and a transponder including a parallel oscillating circuit, these oscillating circuits being sized so that the coupling coefficient between them strongly decreases when the distance separating the transponder from the terminal becomes greater than a predetermined value.

Abstract: A system of contactless electromagnetic transmission between a terminal including a series oscillating circuit for generating an electromagnetic field and a transponder including a parallel oscillating circuit, these oscillating circuits being sized so that the coupling coefficient between them rapidly decreases when the distance separating the transponder from the terminal becomes smaller than a predetermined value.

Abstract: A terminal for generating an electromagnetic field, including an oscillating circuit capable of receiving a high-frequency A.C. excitation voltage via an amplifier and a directional coupler, the oscillating circuit having at least one element of variable capacitance, and circuitry for modifying the value of this capacitance according to the amplitude of a signal extracted from the coupler.

Abstract: The selection of at least one back-modulation element of an electromagnetic transponder from among a plurality of resistive and/or capacitive modulation elements of the load of an oscillating circuit of the transponder, including selecting the modulation element(s) according to a binary message received from a read/write terminal.

Abstract: An amplitude demodulation method and device comprising a converter sampling an input signal having its sampling frequency corresponding to three times the modulation carrier frequency.

Abstract: A method and a circuit for demodulating a signal transmitted by an electromagnetic transponder, including a sensor of a variable which is a function of the load formed by the transponder on an oscillating circuit, a phase demodulator and an amplitude demodulator at least functionally in parallel and receiving a signal coming from said sensor, a summer of the results provided by the demodulators, and a delay element in series with a first one of said demodulators, to compensate for a possible propagation time difference therebetween.

Abstract: A method of transmission between two elements chosen from a terminal and a transponder, each element including an oscillating circuit, a modulator and a demodulator, including simultaneously performing a transmission in amplitude modulation of a signal transmitted from a first to a second element and a transmission of a signal from the second to the first element adapted to being submitted to a phase demodulation in the latter, and wherein the amplitude modulation rate is smaller than 100%.

Abstract: A method and a system of data transmission between a terminal for generating an electromagnetic field and a transponder, the terminal and the transponder each including an oscillating circuit forming an antenna, and the transponder including an electronic circuit adapted to absorbing and giving back power provided by the terminal field, the oscillating circuits of the transponder and of the terminal being capable of transmitting radio-electric signals of determined frequency, this method including causing a detuning of at least one of the oscillating circuits with respect to the determined frequency when the transponder and the terminal are very close to each other.

Abstract: A method and a circuit for demodulating a signal transmitted by an electromagnetic transponder, comprising a sensor of a variable which is a function of the load formed by the transponder on an oscillating circuit, a phase demodulator and an amplitude demodulator at least functionally in parallel and receiving a signal coming from said sensor, a summer of the results provided by said demodulators, and a delay element in series with a first one of said demodulators, to compensate for a possible propagation time difference therebetween.

Abstract: A terminal for generating an electromagnetic field adapted to cooperate with at least one transponder when the transponder enters the electromagnetic field, the terminal including circuitry for determining the distance separating the at least one transponder from the terminal without requiring any transmission from the transponder to the terminal. In one example, the terminal also includes a phase regulation loop that regulates the phase of a signal in an oscillating circuit of the terminal with respect to a reference value.

Abstract: A terminal for generating an electromagnetic field adapted to cooperating with at least one transponder when the latter enters its field, the terminal including an oscillating circuit adapted to receiving a high frequency A.C. excitation voltage, and circuitry for detuning this oscillating circuit with respect to a determined transmission frequency when a transponder is very close to the terminal.

Abstract: An electromagnetic transponder of the type including an oscillating circuit upstream of a rectifier adapted to providing a D.C. supply voltage to an electronic circuit, the electronic circuit including circuitry for transmitting digitally coded information, and the transponder including circuitry for detuning the oscillating circuit with respect to a determined frequency, the circuitry for detuning the oscillating circuit being used when the transponder has to transmit information while it is very close to a read/write terminal.

Abstract: A BPSK encoder is provided with a first circuit which processes a carrier signal and a binary signal to be encoded, and produces an output binary signal having synchronous phase shifts representing a change in the value of the signal to be encoded. Also, the first circuit is provided with a sampling signal from a second circuit. The second circuit includes a delay circuit to deliver a shifted carrier signal that is smaller than the half-period of the carrier signal, and a logic gate for the logic combination of the carrier signal and the shifted carrier signal. The logic gate also delivers a binary sampling signal having at least two leading or trailing edges at each period of the carrier signal.

Abstract: A system for the detection of a load modulation signal by inductive coupling includes an antenna circuit having a coil, a circuit for applying an excitation signal having a predetermined frequency to the antenna circuit, and a current sensor for detecting a current signal in the coil. A phase comparator has a first input receiving the excitation signal, and has a second input receiving the current signal detected by the current sensor. The system also includes a circuit for extracting the load modulation signal from a phase signal provided by the phase comparator. The antenna circuit does not form a resonant circuit equal to or near the predetermined frequency of the excitation signal.

Abstract: A method for testing whether an antenna circuit of a contactless chip card is defective. The antenna circuit is an inductive resonant circuit comprising a capacitor and an antenna coil. The antenna coil of the resonant circuit is excited by inductive coupling using a test coil wherein the excitation is then sharply interrupted. By detecting in the test coil a response signal generated by self-induction in the antenna coil of the resonant circuit and retransmitted to the test coil by inductive coupling, the response signal can be analyzed for determining whether a contactless chip card is defective. Application is well suited to the testing of antenna circuits for electronic portable devices working without contact, such as contactless chip cards, electronic labels, etc.

Abstract: A method for testing an integrated circuit comprising an input capacitance designed to form, with an antenna coil, a resonant receiver circuit with a predetermined natural frequency. The input capacitance is connected to a test inductance chosen to form, with the input capacitance, a resonant test circuit having a resonant frequency substantially equal to the natural frequency of the resonant receiver circuit. The resonant test circuit is excited by an alternating signal provided through a transformer. The testing of inductive integrated circuits working without contact is implemented in a corresponding test system.

Abstract: An antenna coil with low electrical field emissions comprises a flat winding with a specified shape and a conductive screen facing the winding. The conductive screen has substantially the same shape as the winding, and includes a cut-off zone. The screen neutralizes the parasitic electrical field emitted by the winding without disturbing the useful magnetic field which is axially oriented (i.e., oriented perpendicularly to the plane of the coil). Such an antenna coil is applicable to a station for the transmission-reception of data by inductive coupling.