Abstract: An antenna excited by a symmetrical strip line (1) including two peripheral conductors (3, 3') positioned respectively above and below a central conductor (2). It comprises, at the end of the symetrical strip line, a first dipolar radiating element (10), including two quarter wave branches (11, 11') formed by extending each of the peripheral conductors (3, 3') in their plane and a quarter wave branch (12) formed by extending the central conductor (2) in its plane, in an opposite direction; a second dipolar radiating element (20), orthogonal to the first one, including two quarter wave branches (21, 22) formed by the folding of the cental conductor (2) and of one (3) of the peripheral conductors; and distributor and phase-shifter means (30) to excite the dipolar radiating elements (10, 20) by similar respective signals, having the same amplitude but being phase-shifted by 90.degree..

Abstract: An antenna system capable of both circular and linear polarization. The antenna structure includes a symmetrical stripline 90.degree. hybrid coupler, having first and second output branches. A first and second dipolar radiating element is provided, each of the radiating elements having two quarter wave branches formed by folding the stripline conductors. In the first dipolar radiating element, the peripheral conductors of the stripline coupler are folded in the same direction, transverse to the axis of the stripline, and another quarter wave branch is formed by extending the center conductor of the first output branch of the hybrid coupler in an opposite direction. The second dipole radiating element is similarly configured to have two quarter wave branches, comprising the peripheral conductors and the center conductor of a second output branch of the 90.degree. coupler. A second 90.degree.

Abstract: Device and method for permanently checking the integrity of a transmission affected by parameters not directly accessible to measurement and whose influence on the modulus and phase of the field radiated in space can be determined by utilizing a mathematic model, the transmission being from an antenna array. Each antenna is supplied with one or more Hf carrier frequencies, each being modulated in a known way by one or more sinusoidal low frequency signals. First, a recording is made, at least at one point and during a time period T, of the amplitude of the combination of the signal received at this point and of a reference signal, having a fundamental frequency equal to one of the HF frequencies of the signal to be analyzed. Then, the amplitude of low frequency components of the signal thus obtained is extracted and memorized.

Abstract: The device finds application, particularly, in the instrument panels of aircraft, where it comprises: three liquid crystal optical valves, controlled by three electrical signals respectively representing a red image, a green image and a blue image. Two holographic mirrors are utilized, as is a standard mirror and two dichroic strips to illuminate the three valves respectively by three beams, colored red, green and blue, from a single source of white light, while at the same time reducing the space occupied by the optical elements needed to guide the three beams to the minimum. A dichroic cube then superimposes the three beams coming respectively from the three valves and an optical system to form a trichromatic image on a diffusing screen. The optical system collimates the rays coming from the image formed on the diffusing screen to enable an observer to see an image collimated at long distance, with a wide field.

Abstract: A device to eliminate ice formed on the surface of a wall, notably on the surface of an optical or radio-electric window, comprises a piezoelectric material having a vibrating active surface that mechanically cooperates with the wall to be de-iced, and means for the polarization of this piezoelectric material, comprising an AC voltage source and conducting or semiconducting electrodes placed in contact with this material according to a geometry capable of generating, within this material, an acoustic wave that has a direction of vibration which is oriented longitudinally and/or transversally to said surface to be de-iced, the amplitude of this vibration being sufficient to respectively detach and/or break the deposit of ice formed on said surface. The piezoelectric material is preferably a ferroelectric polymer such as a polymer of the group comprising PVF.sub.2, PVF.sub.2 -TrFE, PVDCN-VAc, PVF.sub.2 -TFE and the mixture of these polymers with one another and/or with PMMA or PEMA.

Abstract: A device for reading an optical recording medium which includes a source (1) for emitting a first light beam (F1) along a main optical axis (01); a beam splitter (2) to direct, along the main optical axis, the first light beam towards the surface of the recording medium (5), and to split a second beam (F2) obtained by reflection of the first beam on the surface of the recording medium so as to form a third beam (F'3) directed along a secondary optical axis; a focusing lens (4) between the splitter (2) and the surface of the recording medium to focus the first beam on the surface; a mask to introduce a dissymmetry into the third beam; and at least one detection device (7) receiving at least one part of the third beam (F'3) and giving at least one electrical signal expressing the detection made. In this device, the mask is formed by part of an external surface of the light-emitting source (1), and the splitter (2) is positioned and made so that the mask is in the focusing plane of the third beam (F'3).

Abstract: The interferometer of the invention, of the type with an optical fibre in ring form, with a measuring head (16) connected to a distant processing center (18) by cables, has an optoelectronic detector (17) removed to the center and connected to the measuring head by a multimode optical fibre (19).

Abstract: In a waveguide (1) having slots (2, 3) perpendicular to the axis of the waveguide and cut in a narrow wall of the waveguide, a printed circuit plate (4) is positioned. This plate has patches (5, 7) for coupling with the energy being propagated in the waveguide and microstrip lines (6, 8) connected to the patches to excite the slots (2, 3) with the energy thus tapped. These slot waveguides can be used particularly in array antennas.

Abstract: In the disclosed optic signals processor, a term-by-term subtraction is made of the N homologous values of two series of values resulting from the integration of a light energy that selectively strikes respective photoactive pixels of a charge-coupled device.

Abstract: A process for producing an optical fiber comprising the following stages: a stage of production of a preform having an axis of symmetry and their ends and comprising an optical core as well as at least one cylindrical recess whose axis is parallel to the axis of symmetry of the preform; a drawing stage at a temperature making possible the softening of the drawn part of the preform to obtain a hollow optical fiber, characterized in that it comprises, after the preceding stage of production of the preform: a stage of attachment in a tight manner, to one end of the preform, of a hollow chamber whose cavity communicates with the recess of the preform. The cavity also communicates with a pneumatic regulation device. The drawing stage comprises a pneumatic regulation of the gas contained in the cavity and in the recess with the help of the pneumatic regulation device.

Abstract: Disclosed is a magnetic head comprising chiefly two thin or thick layers of magnetic materials located in a same plane and separated by a gap layer of non-magnetic material, also made in the form of a thin or thick layer. This gap layer forms a determined angle with the plane of the layers of magnetic materials. Methods are also provided for the making of such a head. In particular, these methods make it possible to determine, with precision, the angle of the gap with the plane of the layers of magnetic materials. Applications: magnetic write/read heads for computer peripherals (using tapes or disks), and possibly video tape recorders.

Abstract: A device for optically reading a recording medium is provided, in which a polarization beam separator includes a transparent plate having a phase network associated with a birefringent material, the refraction index of this material having a first refraction index for the polarization of an incident beam and a second refraction index for the polarization of a reflected beam. Thus, in accordance with the embodiment, the detection devices are placed substantially along the emission axis of the optical source.

Abstract: The invention relates to a device for producing microwave energy from an electron beam. The device includes:an electron gun (1), allowing the production of an electron beam (8) in a so-called injection zone (3);a microwave modulation circuit (7), allowing the superimposition of an alternating voltage at a given frequency on the voltage of the beam in the injection zone; the amplitude of this voltage is sufficient for ensuring, during one of its alternations, the transition between the passing state and the virtual cathode state, thus causing a modulation of the current carried by the electron beam;an output microwave circuit (4) functioning at the frequency of the modulation signal and excited by the previous modulated current.

Abstract: The invention relates to a simple, cheap sonar system with high image rate, for the detection of objects and the imaging of sea bottoms. It consists in transmitting n uncorrelated successive codes in a sector of angular width exactly equal to n times the angular width of the reception sector .theta..sub.R, the reception antenna continuing to turn during this time whilst the first signal transmitted has not yet reached the maximum range dmax, and in receiving, in the sector of angular width .theta..sub.R, the echoes of these n codes, coming from n propagation regions which are adjacent in relation to the reception axis, and lying between 0 and dmax in space, each of them having a depth equal to dmax/n.

Abstract: The disclosure concerns an assembly formed by a large-sized antenna with a supporting mast, the working of which brings the ground plane into play, and by a high-power transmitter. To reduce the distance between the transmitter and the radiating part of the antenna, and to reduce the cost of the architectural structure of the antenna and of the room sheltering the transmitter, this room is formed by the base of the mast which supports the antenna. The dimensions and bed of the base of the mast are designed as a function of the space needed and of the stability to be given to the antenna.

Abstract: The detector can be used to detect a wave in the medium infrared range by controlling the detector through optical pumping by means of a near infrared wave. In this case, the detector has a quantum well structure consisting of alternating first layers and second layers, these materials being such that there is a potential well in the conduction band and the valence band of each first layer. The thickness of each first layer is such that the electrons of the conduction band have at least one permitted discrete level of energy, such that the difference in energy between this level and the bottom of the conduction band in the second layers is smaller than or equal to the energy corresponding to the frequency of the wave to be detected; and such that the difference in energy between the fundamental level permitted for the holes in the valence band and the fundamental level permitted for the electrons in the conduction band corresponds to a frequency close to the frequency of the control wave.

Abstract: In an optic coupler, two guides made in the thickness of a substrate are located in two distinct planes. They have sinuous configuration so as to have at least one coupling zone perpendicularly to the planes of the guides. Application: optic switching.

Abstract: A land navigation system, e.g. for a vehicle, which compensates for deviations and drifts of the system sensors. The system has movement sensors, the signals of which are digitalized to make periodic computations of the estimated position of the vehicle. A memory stores the estimated route. A digital cartographic data base is read to extract and memorize the useful zone of the route to be displayed and the coordinates of a readjustment point. A central processing unit for management and computation is programmed to compute deviation measurement between the estimated position and the real position of the vehicle at each readjustment point, and to give compensation parameters that are memorized and used during the next readjustment operation, and so on.

Abstract: An apparatus for generating a magnetic biasing field for recording in a magneto-optical medium, including a coil mounted on a core and connected in parallel with a capacitor and a first switch, and a control circuit for generating a first pulse for opening and closing of the first switch upon each transition of an information signal to be recorded, thereby to produce magnetic flux inversions in the core. A second coil is mounted on the same core as the first coil. Second and third switches are connected in series between positive and negative voltages, and a series connection point between the second and third switches is connected to the second coil, the other end of which is connected to ground. Second and third pulses of fixed duration are applied to the second and third switches based on the trailing and leading edges of the information signal to be recorded, respectively. Monostables are used to generate the first, second and third pulses. The control circuit includes the monostables.

Abstract: Disclosed is an optical component for applications in integrated optics, including a substrate that supports a stack of three polymer layers: a lower layer deposited on the substrate, a central layer and an upper layer, the lower and upper layers having optical indices smaller than that of the central layer which is electrooptical and designed to convey a light beam, the lower layer or the upper layer possessing zones having indices of different values to create a zone of confinement of the light beam in the central layer.