Abstract: A frequency control device comprises, in the form of a phase-locked loop, a phase comparator, a filter, an oscillator producing a local clock signal and two divide-by-M frequency dividers. The dividers receive the local clock signal whose frequency is slaved to N times the frequency of a master clock signal, with M<N, and are looped to the inputs of the comparator. A first of the dividers is reinitialized at the frequency of the master clock signal. A load circuit loads the most-significant-bit stages of a counter included in the first divider with a binary word added to binary elements stored in most-significant-bit stages of a counter included in the second divider, after a resetting of the second divider following a general initialization of the device.

Abstract: A variable-throughput digital modulator receives at an input a transmission digital signal e(t). The transmission digital signal is time-based demultiplexed (1) into first and second elementary transmission signals e1(t) and e2(t) which are applied, respectively, to first (21) and second (22) filtering circuits for delivering first and second filtered elementary signals e1f(t) and e2f(t). A circuit (20) provides throughput switching control to the first and second filtering circuits (21, 22) for selecting a first or second filtering mode corresponding to a first throughput at a first type of modulation or a second throughput at a second type of modulation. A quadrature modulator (3) receives the first and second filtered elementary signals in order to modulate an RDS-compatible carrier f0, and an output filter circuit (5) delivers a filtered modulated carrier signal for broadcast, such as in supplementary data broadcasting in FM radio broadcasting.

Abstract: A method for the transmission of digital data elements including radio paging information elements, wherein the data elements are transmitted according to a technique of transmission implementing a plurality of orthogonal carrier frequencies (the COFDM technique), the signal being organized in frames comprising, firstly, at least one first channel called a fast information channel, comprising at least one symbol of data elements, the carrier frequencies of the symbols being modulated by data elements that are not temporally interleaved, and at least one second channel, called a main channel, comprising at least one symbol of data elements, the carrier frequencies of the symbols being modulated by data elements that are temporally interleaved beforehand, a frame number belonging to a set of predefined frame numbers being regularly inserted into the fast information channel, each of the radio paging receivers being assigned at least one of the frame numbers.

Abstract: An audiovisual program broadcast control center including at least one robot for controlling at least one device containing program information; a central control console for manually controlling the robot; a central programmable automatic controller for controlling the robot; and a data transmission bus for connecting the control console and the automatic controller to the robot.

Abstract: An error-correction method for the coding of source digital data elements to be transmitted or broadcast, notably in the presence of high transmission noise, the method comprising at least two independent steps of systematic convolutional coding, each of the coding steps taking account of all of the source data elements, the method comprising at least one step for the temporal interleaving of the source data elements, modifying the order in which the source data elements are taken into account for each of the coding steps, and a corresponding iterative decoding method using, for the decoding, at each iteration, an intermediate data element obtained by the combination of the received data element with a data element estimated during the previous iteration.

Abstract: A process for broadcasting conditional access programs which permits a progressive access. Scrambled program data is transmitted along with partial access checking messages and complete access checking messages such that subscribers having a partial access right may descramble portions of the scrambled data corresponding to information regarding only the identity of the conditional access programs, and subscribers having a complete access right may descramble the remainder of the scrambled data and view the conditional access programs. The conditional access programs may be television pictures, radio programs, or data broadcasts.

Abstract: A method for the decoding of digital data obtained according to a convolutional coding and transmitted on a noise-ridden channel aimed at improving the methods of maximum likelihood decoding such as the Viterbi algorithm consisting in associating, with each estimation s(t) of the corresponding source digital element a(t), a weighting coefficient m(t) representing the reliability of the estimation s(t), the estimation s(t) taking account of the values of a first series of L received samples, and the weighting m(t) taking account of the values of a second series of N samples received, N being strictly greater than L. In a preferred embodiment, a second trellis is associated with the standard first decoding trellis, a trace-back being done in the second trellis on two concurrent paths, used to revise the weighting coefficients obtained at output of the first trellis.

Abstract: A device for the reception of digital data broadcast at a high bit rate for reception by mobile receivers is disclosed. The device operates under adverse conditions of multiple propagation corresponding to the Rayleigh process and imperfect frequency tuning to minimize the inter-symbol interference in the frequency domain. The device receives a digital signal having digital elements distributed in the frequency-time space f-t and transmitted in the form of symbols each constituted by a multiplex of N orthogonal carrier frequencies modulated by a set of digital elements and broadcast simultaneously. The device includes a module for transposition by a local oscillator, baseband filtering and analog-digital conversion, a temporal windowing module for the selection of the useful samples and a mathematical transformation module, the temporal windowing module applying a Nyquist window type of temporal window with non-zero roll-off.

Abstract: A process for the transmission and reception of scrambled conditional access programs, which are synchronously transmitted with entitlement control messages (ECM), with a reduced program switching time. The entitlement control messages (ECM) have check words, which are changed after a period of time called a phase, for descrambling the conditional access programs. The process includes transmitting main check messages (ECMp) for a main access program at a first frequency (Fp) and transmitting secondary check messages (ECMs) for secondary programs at a lower, second frequency (Fs). The secondary check messages (ECMs) are transmitted between two successive transmission of the main check messages (ECMp) such that all of the secondary check messages (ECMs) for each of the secondary programs are transmitted in a single phase. Therefore, a check word for any program is quickly acquired and program switching time is reduced.

Abstract: A video analysis system for editing an edited or broadcast televised program, which is a succession of images of order k, that can be used for post-production techniques such as multilingual post-production techniques. The system comprises a circuit for measuring the time variance of the composition of the images, establishing, time-wise, the composition of the images so as to establish an image difference signal and scenic-activity parameters of the broadcast program for a group of at least two successive images of order k-1, k. An analysis circuit makes it possible to establish from the scenic-activity parameters, data representative of the cutting-up into shots, consisting of a group of p successive images, of the broadcast, televised program.

Abstract: An antenna comprises a quarter-wavelength skirt antenna adapted to be disposed over an artificial ground and comprising a vertical cylindrical tube closed at the upper end and a coaxial feed inside the tube. The radiation pattern of the skirt antenna is essentially omnidirectional with a low elevation angle. The skirt antenna is combined with a helical antenna disposed vertically above the skirt antenna and coaxially therewith. The surface closing the upper part of the tube of the skirt antenna constitutes a reflective plane for the helical antenna favoring a hybrid radiation mode specific to the latter, partially axial and partially radial, by lowering the receive lobe of the radiation pattern towards an elevation angle suitable for receiving signals transmitted via satellite. A coupling device combines the signals received by each of the two antennas and feeds them to a common coaxial line.

Abstract: A system for the transmission of digital data elements corresponding to at least one application each comprising at least one stream of data elements, the data elements being constituted by digital elements distributed in the time-frequency space and transmitted in the form of symbols constituted by a multiplex of orthogonal carrier frequencies modulated by a set of the digital elements and broadcast simultaneously, the symbols being organized in successive frames, each frame being organized in at least one data conveying channel, each channel being constituted by a succession of at least one consecutive symbol. The data elements may advantageously be transmitted, in each channel, either in transparent mode or in packet mode.

Abstract: A method and device are provided for encoding-decoding an HD digital television signal into a narrow band encoded signal. The HD digital television signal is representative of high definition images sampled at a frequency f1, and the narrow band encoded signal corresponds to a narrow band signal sampled at f2, wherein f2<f1. Narrow band encoding is achieved by horizontal compression by decimation of the image lines of the HD digital television signal so as to bring the number N1 of useful pixels per image line to a value N2=.alpha. of the sampling frequencies, so as to thus form an encoded signal representative of an image line and obtain reduced format high definition images. A narrow band encoded signal representative of digital television signals can thus be broadcast over an HD-MAC NB type channel.

Abstract: The receiving antenna comprises at least two sectors or sections of paraboloids focusing the radiation onto their axes at points F.sub.1 and F.sub.2 respectively offset by a whole number of wavelengths of the received radiation. Each sector or section is associated with a helicoidal source located in its focal zone and having the same axis as that of the corresponding sector.

Abstract: Method of electronic payment by chip card.According to the invention, each token carries a number making it possible to check its authenticity.The invention is used for electronic payment.

Abstract: A method for the coding of images represented by source signals by means of which a luminance signal is formed by linear combination, using positive coefficients of the source signals, and at least one color signal, the luminance and color signals being digitized, sampled at the same resolution, and subjected to a reversible mathematical transformation in the frequency domain. The method comprises the steps of quantizing and assigning a code value to the continuous component and to each component of a set of alternating components of the transformed luminance signal, and quantizing and assigning a code value to only the continuous component of each of the transformed color signals, a set of alternating components being reconstructed by estimation during the decoding for each of the transformed color signals. The method can be applied to color images of any type represented as the superimposition of monochromatic images, whether the images are still images or motion images.

Abstract: The antenna particularly for domestic, collective or community installations, receives plural telecommunication beams and comprises a preferably paraboloidal fixed reflector with an axis of symmetry. At least one grating of annular diffraction members is substantially symmetrical with regard to the axis and is placed parallel to the reflector. The grating defines first and second focal points symmetrical to the axis towards which are susceptible to converge first and second beams directed substantially parallel to straight lines going through the centre of the grating and through first and second focal points respectively. A microwave head can sweep the focal plane along a focal line, or several microwave heads are positioned on a gantry thereby receiving or emitting plural beams, though the reflector is fixed.

Abstract: A method for the broadcasting of digital data, intended to be received notably by mobile receivers moving about in an urban environment, that is, under conditions of multiple propagation and in the presence of parasites and jamming, enabling a coherent demodulation under such conditions of reception. This method is one for the broadcasting of digital data, notably for radio broadcasting at a high bit rate towards mobile receivers, of the type providing for the distribution of the data in the form of digital elements in the frequency-time space f-t and the transmission of symbols each constituted by a multiplex of N orthogonal carrier frequencies modulated by a set of digital elements and broadcast simultaneously, certain of the digital elements being reference elements with a value and position in the frequency-time space f-t that are known to the receivers.

Abstract: In accordance with the present invention, the number of bits used to code a frame of video is controlled by controlling the frame size. In a preprocessing stage (40) of a video coding circuit (10), each frame of video is processed by a low pass anti-aliasing filter (43,44) in the horizontal and vertical directions. The cutoff frequencies in the horizontal and vertical directions are determined by a desired frame reduction factor in the corresponding direction. Then to reduce the sampling rate in each dimension, each frame of video is processed horizontally and vertically by a shift varying filter (45,46). When the sampling rate in both the horizontal and vertical directions is reduced by M/N, the number of code bits decreases linearly with M/N.

Abstract: A movement estimation method and system are disclosed for high definition digital television frames. The movement is estimated for a current block Bc of the even fields T.sub.2k, 2r-1 of the uneven frames with which n movement vectors are associated, with the current block Bc of the even fields T.sub.2k, 2r of the even frames there is associated, by relative addressing, a movement vector with respect to s vectors of the preceding frame I.sub.2r-1 surrounding the frame B'c of the current block Bc. The s vectors are chosen by eliminating the vector redundancies among the n vectors. The invention is applicable to broadcasting and transmission of digital television signals by HD-MAC or HD-MAC NB narrow band channel.