Abstract: A method for reducing the peak factor of a signal transmitted in a frequency band comprising several channels, the signal using a plurality of channels in the band comprises: a step of clipping the signal, a step of subtracting the clipped signal from the signal, so as to obtain a peak signal, a step of filtering the peak signal with the aid of a multichannel filter configured to comply with a predetermined spectral mask for each of the channels used by the signal, and a step of subtracting the filtered peak signal from the signal. A device for emitting a multichannel signal implementing the method for reducing the peak factor is also provided.

Abstract: A system and a method for communication between at least one user in a high-frequency HF communication system comprising at least one transmission site and at least one reception site, the two sites being remote from one another by a distance D, comprises at least the following steps: scanning the signals or frequencies by using a wide band receiver, detecting whether there is a request to establish a communication link contained in the signals received on the receiver, if yes, then transmitting this link establishment request to the transmitting equipment item which will check whether it is possible to establish a link and, if it is, which will determine a possible configuration and establish a communication mode for the mobile user, if not, then returning to the step in which the signals received on the reception site of the system are scanned.

Abstract: A method for reducing the peak factor of a signal transmitted in a frequency band comprising several channels, the signal using a plurality of channels in the band comprises: a step of clipping the signal, a step of subtracting the clipped signal from the signal, so as to obtain a peak signal, a step of filtering the peak signal with the aid of a multichannel filter configured to comply with a predetermined spectral mask for each of the channels used by the signal, and a step of subtracting the filtered peak signal from the signal. A device for emitting a multichannel signal implementing the method for reducing the peak factor is also provided.

Abstract: A method for managing the HF frequencies in a broadband communication network, comprises the following steps: determining the range of passing frequencies for a user for a given link and SLA service; establishing the set of authorized frequencies S? in the transmission range of the user with the different power and modulation configurations for each frequency; analyzing the received spectrum in order to determine the frequency or frequencies already used and deciding, on the basis of their associated usage type, whether they must be excluded; for each possible frequency fl of the set S??, determining the necessary power , i=1 . . . N, j=1 . . . m for each of the m possible rate/waveform configurations, taking into account the power limit on each frequency fl; allocating the frequencies fl of the set S?? to the different users, their modulation and their power, by taking account of multi-carrier constraints.

Abstract: A method for managing the HF frequencies in a broadband communication network, comprises the following steps: determining the range of passing frequencies for a user for a given link and SLA service; establishing the set of authorised frequencies S? in the transmission range of the user with the different power and modulation configurations for each frequency; analysing the received spectrum in order to determine the frequency or frequencies already used and deciding, on the basis of their associated usage type, whether they must be excluded; for each possible frequency fl of the set S??, determining the necessary power {tilde over (P)}ij, i=1 . . . N, j=1 . . . m for each of the m possible rate/waveform configurations, taking into account the power limit on each frequency fl; allocating the frequencies fl of the set S?? to the different users, their modulation and their power, by taking account of multi-carrier constraints.

Abstract: A method is provided for estimating the polarization ellipticity of an antenna response signal to an incident electromagnetic wave received on a crossed-loop antenna or an Adcock antenna array. The method comprises at least the following steps: measuring the phase offset ?? between the signals acquired respectively on the cosine and sine path of the antenna; measuring the ratio R between the amplitudes of the signals acquired respectively on the cosine and sine path of the antenna; determining the ellipticity angle ? based on the phase offset ?? and on the ratio R. The invention applies notably to the discrimination of ionospheric waves from ground and/or sea waves, in particular for a surveillance, eavesdropping, or goniometry system using HF band signals.

Abstract: A method of measuring the direction of arrival ? of radio signals in the HF band received by a crossed loop antenna includes, in a preparatory calibration phase, acquiring and recording the measurements made by the antenna of a calibration signal which varies in its frequency and bearing angle; and in a measurement phase in which the bearing angle or angles of arrival of signals detected by the antenna is or are determined, acquiring the signals detected in at least one frequency channel, and then, for each frequency channel fi, correlating the acquired signals with the recordings having frequencies close to fi, resulting from the calibration, and determining the direction of arrival of the signals by finding the bearing angle ? for which the maximum correlation is reached.

Abstract: A method is provided for estimating the polarization ellipticity of an antenna response signal to an incident electromagnetic wave received on a crossed-loop antenna or an Adcock antenna array. The method comprises at least the following steps: measuring the phase offset ?? between the signals acquired respectively on the cosine and sine path of the antenna; measuring the ratio R between the amplitudes of the signals acquired respectively on the cosine and sine path of the antenna; determining the ellipticity angle ? based on the phase offset ?? and on the ratio R. The invention applies notably to the discrimination of ionospheric waves from ground and/or sea waves, in particular for a surveillance, eavesdropping, or goniometry system using HF band signals.

Abstract: A method of measuring the direction of arrival ? of radio signals in the HF band received by a crossed loop antenna includes, in a preparatory calibration phase, acquiring and recording the measurements made by the antenna of a calibration signal which varies in its frequency and bearing angle; and in a measurement phase in which the bearing angle or angles of arrival of signals detected by the antenna is or are determined, acquiring the signals detected in at least one frequency channel, and then, for each frequency channel fi, correlating the acquired signals with the recordings having frequencies close to fi resulting from the calibration, and determining the direction of arrival of the signals by finding the bearing angle ? for which the maximum correlation is reached.

Abstract: A method of structuring a database of objects, the objects each comprising one or more attributes, the attributes being ordered, the method being executed by at least one computer processor connected to a memory, the method classifying in memory the objects in a structure composed of a list CL of sets of formal concepts Ci, includes at least the following steps: create several groups of attributes SAi; for each of said groups SAi, construct a closed set Pi composed of all the attributes common to the objects comprising at least the attributes of said group SAi; determine the list CL of formal concepts Ci ordered in the lexicographic order, by successively determining the formal concepts in order of increasing intent, the intent F of a formal concept Ci being formed by a set of closed sets Pi.

Abstract: A method of measuring the bearing angle of arrival ? of HF band electromagnetic signals received by a crossed loop antenna or an Adcock antenna array includes measuring the phase difference ?? between the signals acquired in the sine and cosine paths of the antenna; measuring the ratio R of the amplitudes of the signals acquired in the sine and cosine paths of the antenna; and determining the bearing angle of arrival ? of the wave as a function of the phase difference ?? and the ratio R. The method is applicable to the detection and location of electromagnetic signal transmitters, particularly in the maritime field.