Thomson-csf

Jean Desbois

Pierre Tournois

Marc Solal

Philippe Defranould

Pierre Dufilie

Jean-Michel Hode

A filter with surface acoustic wave resonators using an equivalent electrical bridge structure to obtain a good form relationship, i.e., a relationship between the filter rejection band and its pass band. Bridge arms advantageously include the paralleling of several resonators, thereby not requiring additional electrical elements as in the background art which provides for the use of series-connected resonators. Particular implantation methods for preparing equivalent structures to paralleling several resonators are also disclosed.

Filter with surface acoustic wave resonators

Surface acoustic wave filter utilizing the coupling of three acoustic

Surface wave filter filtering delay transfer function

In a transducer for surface waves, an alternating succession of transmitter cells and reflector cells is used. The transmitter cells transmit surface waves in phase opposition, leftwards and rightwards. The reflector cells have a reflection coefficient that is in phase opposition between the left-hand side and the right-hand side. The waves transmitted by the transmitter cells interfere with the waves reflected by the reflector cells, destructively in one direction and constructively in the other direction. This enables the making of transducers with spacings equal to .lambda./4 and .lambda./6 only.

Unilateral surface wave transducer

A method for the correction of surface wave devices consists of measuring the transfer function of an entirely finished surface wave device and then designing a surface wave corrective filter, the transfer function of which enables the correction of the transfer function of the preceding device. The method makes it possible to correct, in particular, RAC type dispersive filters.

Method for the correction of a surface wave device, especially for a

The system permits the multiplex telecommunication through the medium of an optical carrier wave. The system comprises a source of coherent light whose optical spectrum is dispersed in an optical device comprising a pair of diffraction gratings. A plurality of light modulators are disposed in the path of the spread out beams and controlled by electric signals which carry items of information. Output optical means collect the modulated spectral components.

Multiplexed optical communication system

A piezoelectric substrate is subjected to the continuous excitations produced by a high-frequency electric field of fixed radian frequency .alpha. applied between its two opposite faces; high-frequency electrical pulses of radian frequency .alpha..sub.p are applied to the periodic network of conductors illuminated by the image; the electrical conductivity at the surface of the substrate at each point is made a function of the illumination directed towards said point, for example by the application of a photoconducting semi-conductor covering the network or by a substrate whose conductivity is directly modulated by the incident light. The non-linear interaction between the two substrate excitations induces a surface wave whose intensity is modulated by the luminous intensity and which is picked up by the transducers. Application with fixed .alpha..sub.p, to the point by point read-out of a linear optical image and with .alpha..sub.p = .alpha..sub.p (t) to the analysis of its spatial frequencies.

Piezoelectric device responsive to optical image for generating an

A device for reading two-dimensional optical images. It comprises a piezoelectric substrate on which two transducers transmit elastic waves in two separate directions, and a semiconductive and photoconductive layer arranged near the surface of the substrate, in which a nonlinear interaction occurs opposite the point where the two said directions converge. This point of convergence forms a reading point of the image which is projected onto the photoconductor, this point moving as a function of time along a straight line which forms an analysis line of said image.

Device for the two-dimensional reading of optical images, using elastic

A system is provided for reading acoustic images such as those obtainable in an elastic medium as a result of the focusing of, or interference between, acoustic waves. The image analysing device comprises a substrate made of piezoelectric material which is provided on one face with an interdigital array and an electro-acoustic transducer. The system permits to read acoustic images formed at the free surface on the opposite face of the substrate or at a certain distance from its free surface in contact with an elastic propagation medium.

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Roquefort les Pins, France

Jean Desbois