Thales

Thomson-csf

Pierre-André Laurent

A constant-amplitude and continuous-phase modulation method for modulating digital data and for demodulating said modulated signal, said data taking the form of symbols a(n) that can take a number M of states at least equal to 2, the method including, in transmission, use of a voltage-controlled oscillator (VCO) for which the control is the sum of pulses he(a(n), t&#x2212;n T), the form and the amplitude of which depends on the value of a(n); and, in reception, use of a single impulse response filter C0(t) regardless of the value of M in transmission, said functions he and C0 having a number of parameters that are optimized in the design of the system in order to obtain at the output of the filter C0 a constellation that is as close as possible to the theoretical constellation.

System and method for sending and receiving a digital signal over a radio pathway

A system and method for estimating and tracking the frequency offset for a transmission system whose bandwidth is not insignificant with respect to the central frequency, the system transmitting a waveform including fixed carriers whose level is substantially greater than that of the carriers transporting the information, the carriers having frequencies F. . . F, and the useful signal carrying the information. The system has N banks () of band-pass filters with, each bank having P filters, suitable for covering all of the values that the frequencies F. . . Fmay take after Doppler offset. A filter output is connected to a quadratic envelope detector. P adders () are suitable for adding the corresponding outputs of the N banks of filters. A system () detects the position of the two largest maxima from the P sums and validates the position of the largest maximum. A system () stores the positions of the two largest maxima and their 'weight' and for predicting the current value. A system () validates/replaces the position found. A system () converts the positions into estimated Doppler and filters the latter through a low-pass filter.

Doppler tracking method and device for a wide band modem

A device and a method for the rejection of interference in a payload signal are described. The method includes evaluating the interference phase and evaluating the instantaneous amplitude of the interference by the least error squares method, forming a ratio r=(B/(A+B)) where A is the real part of the amplitude of the interference and B is the complex part of the amplitude of the interference. If r is below the threshold value r, the signal is corrected by replacing the central sample of the signal by a weighted sum moderated by the central sample and neighboring samples.

Method and device for the rejection of self-adaptive interference

A system and method to provide continuity of service in a radio broadcasting system, wherein the radio broadcasting system includes at least one modem using the COFDM technique, and transmits N time-frequency cells modulated independently of one another. A number Nof cells conveying digital audio signal Sand a number Nof cells conveying analog audio signal Sare transmitted to a receiver. When the receiver cannot decode the signal in the Ncells, the receiver replaces the digitized audio signal Swith the analog signal S.

Radio broadcasting system and method providing continuity of service

A short wave high efficiency radio broadcasting transmitter for digital transmissions. The transmitter includes a power tube in which the grid is excited by a variable phase signal through an excitation device and in which the anode is amplitude modulated by the output signal from a modulator. The phase and amplitude signals applied to the grid and anode of the tube respectively represent the phase and amplitude of the complex signal to be transmitted. The amplification characteristic of the excitation device remains linear for low amplitudes of the signal to be transmitted and operates under saturated conditions when the amplitude of the signal to be transmitted exceeds a given threshold value, so that the amplification characteristic of the transmitter as a whole remains linear independently of the amplitude of the signal to be transmitted. Such a transmitter may find particular application as a short wave transmitter.

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Bessancourt, France

Pierre-André Laurent