Thomson-Csf

Other

Pierre A Laurent

Gerard Auger

Herve Ganem

Ljubimko Milosevic

Patrick Mocchi

Denis Rochette

Process for the vector quantization of low bit rate vocoders

The method disclosed consists in analyzing the vocal signals in consecutive windows, in quantifying, on a determined number m of levels, the vocal signal in each of the windows and in measuring, in each of the windows, the vocal signal in each of the windows and in measuring, in each of the windows, the r-m-s value of the samples of the vocal signal. It consists constructing, in a vector space with n dimensions having, as its first base, the unit vectors (E.sub.0 to E.sub.n-1) of the energies measured on n consecutive windows, a resultant energy vector E corresponding to the sum of n energy vectors measured respectively in n windows of analysis of the vocal signal, then in achieving, in this space, a change of base having, as its first main axis, an oriented axis of unit vector having, as its components, the unit vectors of the first base, to project, in the new base obtained, the resultant energy vector. Codings on q bits such that 2.sup.q =m of the component of the resultant vector projected on the main axis of the new base and on a reduced number of bits smaller than q, of the components of the energy vector projected on the n-1 other main axes of the vector space defined in the new base, are then made. An embodiment of a device corresponding to n=3 is described.

Method and device for coding the energy of a vocal signal in vocoders

The method disclosed comprises the steps of: cutting up the signal into frames, sampling each frame to obtain a digital signal comprising a determined number n of samples, pre-emphasizing the digital signal, filtering the pre-emphasized digital signal by means of a high-pass digital filter to obtain a filtered digital signal, measuring, in each frame, the maximum energy of the pre-emphasized signal and the maximum energy of the filtered digital signal, to achieve an energy ratio R between the maximum energy of the filtered digital signal and the maximum energy of the pre-emphasized digital signal. The method also comprises the steps of computing, between two limits, the mean long-term values of the maximum value of the energy of the filtered signal and of the energy ratio and of computing, on the basis of the mean long-term values, four threshold values, two of them being maximum values, forming two lower limits of the speech state for the filtered signal and the energy ratio respectively, and two of them being minimum signals, forming two upper limits of the noise state for the filtered signal and the energy ratio respectively, to compare, with these threshold values, the maximum energy of the filtered signal and the energy ratio, to decide on the presence of the vocal signal in the noise-infested signal when the maximum energy of the filtered digital signal, or the energy ratio, is respectively greater than their maximum threshold values.

Method and device for the detection of vocal signals

The continuous phase angular demodulation method disclosed digitally processes the signal in baseband after having over-sampled it with reference to the bit period. The processing consists in routinely demodulating sub-sets of differential phases at the bit period T.sub.b shifted with respect to one another by fractions T.sub.b /q of this period, in correcting them, a priori, by the phase deviations associated with a set of pre-defined d frequency drifts and in computing, for the d.q sets thus obtained, a noise criterion. The set of demodulated bits chosen is the one that reduces this noise criterion to the minimum. The set of bits then enables computation of the phase variation emitted and, using this variation and the measured variation, the real frequency drift. Another demodulation taking this drift into account is done for the q sets of initial differential stages and the set minimizing the noise criterion is then chosen and fixes the synchronization bit by the sampling instants associated with it.

Method and device for the demodulation of signals with constant envelope

A method and device are provided for multistate modulation and demodulation with adjustable protection level, consisting in separating the binary signals, before demodulation, into critical and non critical signals, in attributing to the non critical signals all the states of the modulation and in attributing to the critical signals a reduced number of states which are, in the modulation diagram, the furthest removed from each other.

Method and device for multistate modulation and demodulation with

The symbol synchronization method for the symbol demodulation of a digital signal uses E sequences of samples taken from the demodulated signal, each sequence being offset with respect to the following one by a fraction of the symbol period Ts/E. On the basis of each one of E sequences of samples (Si1,Si2, . . . SiN) ranging from from i=0 to E-1, a value F(i) of a pre-defined function F, optimized according to the type of modulation made at emission, is calculated. This function, which can be identified with a sine model, A+B COS(i-io)2.pi./E, can be used to determine io characteristic of the synchronization time-shift and, if necessary, A, characteristic of the d.c. offset, and B, characteristic of the variation in levels due to reception conditions. These values are used to correct the synchronization signal and, if necessary, the d.c. and the decision thresholds of the decision circuit during the symbol demodulation.

Method and device for symbol synchronization and their application to

The demodulator is for use with an angle modulated signal conveying a sequence of binary symbols. The signal is modulated at constant envelope and with continuous phase and may be treated as a sequence of elementary pulses that have been amplitude modulated using a principal function F.sub.p (t) derived from the frequency pulse characteristic of the modulation. The demodulator comprises two filters matched to the principle function and connected to receive quadrature components constituting the complex envelope of the received signal. The filters are followed by samplers. A calculating circuit operating at the bit rate calculates metric increments on the basis of P stored complex samples and transmits the increments to a decision circuit which performs a dynamic programming algorithm to determine the values of the bits in the sequence recursively.

Demodulator for constant envelope and continuous phase signals which are

A device for demodulating signals modulated by frequency-shift keying comprises a surface-wave filter having two input transducers supplied in parallel by the modulated signals and separated by a given distance, and an output transducer composed of electrodes e.sub.1 to e.sub.n+1 and e'.sub.1 to e'.sub.n+1. The signals delivered by the electrodes e'.sub.1 to e'.sub.n+1 are applied to the inputs of an algebraic summing device through switches I.sub.1 to I.sub.n+1 controlled by logical signals T.sub.1 to T.sub.n+1. The output of the summing device is connected to the output of the demodulating device through a threshold device; programming of the signals T.sub.1 to T.sub.n+1 makes it possible to provide a filter which is matched with the signals to be demodulated.

Device for demodulating signals modulated by frequency-shift keying

In a process for the afterburning of the combustible pollutants from an internal combustion engine, in order to automatically reduce the secondary induction rate when power increases without using a controlling valve actuated by the carburettor venturi depression, there is provided a volumetric efficiency of the secondary air pump linked to and activated by the engine and a volumetric efficiency which decreases when the ratio between its back pressure and suction pressure increases, this reduction being achieved through the proper selection of the pump volumetric comression ratio r: between 0.6 c and 1.3 c when a steeply decreasing trend is required, and above 1.3 c if a slower and slower decreasing trend is required. To perform this process an afterburner apparatus has a nitrogen oxide reducing catalyst placed inside the afterburner reactor on the gas stream immediately at the outlet of a torus, in which the gases are homogenized and their reaction with preinjection air is terminated.

Process and apparatus for afterburning of combustible pollutants from an

The herein disclosed synchronization extractor is designed to recover a train of useful pulses of given recurrence period T from an input signal containing both useful pulses and parasitic pulses. Each period T is divided into n sampling intervals of a duration less than or equal to that of the pulses. The pulses present in the several intervals are respectively counted by n reversible counters. Backward-counting pulses, having a recurrence period which is greater than the period T but less than the recurrence periods of the parasitic pulses, are applied to the counters simultaneously. The useful pulses are collected from that counter in which the mean rate of the forward-counting pulses exceeds that of the backward-counting pulses.

Synchronization extractor

An apparatus for afterburning the combustible pollutants from the exhaust gases of an internal combustion engine in a reactor, in which secondary air is introduced. Upstream of the reactor, a chamber in the form of a torus is provided, through which the exhaust gases from a maximum number of cylinders flow before entering the reactor. A first obstacle, acting as a flame holder is disposed inside the torus. The reactor comprises a chamber whose inner surface is approximately a surface of revolution, and mounted inside of which is a second obstacle, acting as flame holder, substantially along the axis of revolution. The second flame holder has a diameter large enough to provide a contact time of 1 to 3 .times. 10.sup.-.sup.3 seconds of the gas flow in a recirculation zone surrounding the second flame holder, the diameter of the second flame holder being 15 to 40% of the reactor diameter.

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Bessancourt, France

Pierre A Laurent