Abstract: An electron source is formed by at least one elementary electron emitter in which an emissive point having a very small radius of curvature operates on the field emission principle and produces an electron beam, the intensity of which is independent of any possible variations of electron emission. The emissive point cooperates with an extracting electrode, and a control electrode having a negative potential with respect to the extracting electrode is placed downstream of the extracting electrode with respect to the direction of propagation of the beam.

Abstract: The electron source disclosed comprises a solid having a first semiconductor layer capable of releasing electrons under the effect of an electrical field, means to make at least one of its faces partially transparent to at least one part of the released electrons, and to enable this part of the electrons to be ejected from the solid, and a second unstable composite semiconductor layer having a structure having a negative differential resistance located between the first layer and its face which is at least partially transparent, in contact with the first layer. The electron source further includes means to form, with said first layer and the composite layer, an electrical resonant cavity.

Abstract: In a noise reducer for microwave amplifiers working by pulses, a small portion of the amplifier output signal is diverted through an ancillary channel. The amplitude of the pulses of this diverted signal is greatly reduced by a limiter. The noise between the pulses can then be processed in an amplifying circuit and in a phase-shifting circuit so that, by combining the main signal in a second coupler, the noise between the pulses is eliminated. This invention can be applied to transmission amplifiers forming part of a transmission/reception set where reception takes place between the transmission pulses.

Abstract: A klystron is provided for supplying power with optimum efficiency across a variable impedance load. To attain this result, the field in the output cavity of a klystron is detected by a probe. This field supplies the image of the voltage at the terminals of the interaction gap. The signal supplied by the probe is used for adjusting the amplitude of the ultra-high frequency voltage applied to the input cavity so that the voltage of the terminals of the interaction gap remains less than the tolerable maximum whatever the ratio of standing waves reflected back by the output device.

Abstract: A device for producing televised pictures with a high degree of resolution comprises a photosensitive matrix which receives an optical image, and an electromechanical apparatus for displacing the matrix with respect to the optical image formed thereon. The displacement is equal to half the size of an elementary modual, or pixil, defined by the intersection of the lines and columns of the matrix.

Abstract: For reducing as much as possible the dimension of converging electron beams, at their point of minimum section, the invention provides in this zone an ionic charge counterbalancing the space charge of the beam, by means of an equipotential electrode disposed about this point. Said electrode is the tube in the figure. When further modulation is applied to the beam, the electrode which ensures it is placed after it in the path thereof.

Abstract: This oscillator comprises a periodic structure line constituted by a succession of vanes having an orifice in which propagates a linear electron beam. This line is placed over a cavity constituted by a straight parallelepiped which has a rectangular base, whose dimensions are determined in such a way that it behaves like a waveguide at the cut-off frequency, along the longitudinal axis of the line and on a transverse magnetic or TM.sub.mn mode with m=1, 3, 5 etc. and n=1, 2, 3, 4 etc. Coupling slots are provided on the cavity between two successive vanes and in a gap between pairs of vanes. The anode voltage of the beam and the distance between two successive vanes are selected in such a way that the cavity resonates at the cut-off frequency and on the .pi. mode. Applications include measuring oscillators and heterodyne radar transmitters and receivers.

Abstract: The areas of the walls 1 separating two adjacent cavities that are located on the periphery of the opening 3 for allowing through the electron beam, and whose thermal resistance is greatest, are those comprised between this opening 3 and a cavity coupling opening 2. Owing to the opening 3 for allowing through the electron beam (elliptical, centered on the axis of the line 00', with the large axis of the ellipse merging with the axis of symmetry AA' of the coupling openings 2 intersecting the axis 00'), these areas are the furthest away from the axis of the line 00' along which the electron beam is propagated. The invention is applied to microwave tubes and in particular to travelling-wave tubes.

Abstract: Parametric coupling device for traveling-waves, comprising a first signal wave, a second idler wave and a third pump wave, wherein a transmission line for said traveling-waves is formed on a substrate of dielectric material, which comprises a virtually continuous network of non-linear interaction elements, modulated by the pump wave, and so modulating the conduction properties of the transmission line and enabling intermodulation to be set up between the various traveling-waves. The virtually continuous network of non-linear interaction elements is a substantially plane network, each non-linear interaction element being at a distance a, or pitch of the network, from a neighbouring non-linear element, the distance a being less than the smallest of the wavelength of the signal, idler and pump waves and the plane network being disposed in the neighborhood of the upper surface of the transmission line.

Abstract: An input transducer for a surface wave filter with a transfer function T(F) the inverse Fourier transform of which is a function I(t) having maxima the amplitude of which vary within wide limits; such an input transducer comprises at least two elemental transducers of which one has a pulse response comprising the high-amplitude maxima of I(t), while the other(s) has/have a pulse response comprising maxima equal to n times the low-amplitude maxima of I(t); the first is fed by the signal to be filtered; the other(s) is/are fed by a signal equal to 1/n of the signal to be filtered. Such a transducer arranged at one end of a piezoelectric substrate of which the other end comprises a wide-band output transducer, provides for the construction of high quality filters.

Abstract: A high frequency elastic bulk wave filter, using the variation as a function of frequency of the direction in which a bulk wave travelling through an elastic body is diffracted by a flat surface of that body, formed with a grating. The bulk wave beam corresponding to the signal to be filtered, impinges under normal incidence on the grating, the profile of which is designed to minimize the amount of energy contained in the non-dispersive beam specularly reflected by the grating. The filter further comprises a transducer to collect the diffracted wave, applied to an inclined surface, which is parallel to the wave plane of the diffracted wave.

Abstract: An input transducer for surface wave filters having an asymmetrical transfer function comprises two pairs (5 and 6) of interdigital combs disposed side by side on the same piezoelectric substrate staggered by one quarter of the acoustic wavelength, one having a symmetrical transfer function and the other an anti-symmetrical transfer function. The asymmetrical transfer function filter is obtained by summing the two acoustic waves generated by such an input transducer in a wide band output transducer.

Abstract: Cavity resonator electronic tubes, in particular magnetrons, with an electronic tuning system. The tuning systems in accordance with the invention consist of multipactor elements arranged directly within the resonant volumes of the tube cavities. Frequency tuning can be effected either by switching between two predetermined frequencies or by continuous change of the frequency.