摘要:
A device for receiving and/or emitting an electromagnetic wave having a free space wavelength λ 0 comprised between 1 mm and 10 cm, comprising a medium (11) of solid dielectric material and the free space wavelength λ 0 corresponding to a wavelength λ inside the medium, a plurality of conductor elements (12) incorporated inside the medium and spaced apart from each other of a distance lower than λ/10, and one antenna element (13). The conductor elements form small loop elements. A tuned conductor element among the conductor elements has a first end at a distance from the antenna element which is lower than λ/10, and has an electric resonance frequency corresponding to the wavelength λ.
摘要:
Method for focusing an electromagnetic or acoustic wave on a point near which one or more diffusers are placed, comprising a learning step in which the pulsed responses hij (t) between the focus point and each antenna (2) of the network are determined. Waves corresponding to signals Sji(t) = Si(t) ⊗ hij(-t), where Si(t) is a function of time and hij(-t) is a temporal inversion of the pulsed response hij(t), can then be transmitted from said antennas (2) of the network.
摘要:
According to the invention, a wave, corresponding to a signal s(t), may be temporally inverted by application of a first transformation to lower the central frequency thereof to produce a first set of transformed signals Ki(t), then a second set of transformed signals K'i(t) is produced, representing the temporal inversion signal s(-t) and a third transformation is applied to said second set to generate the temporally-inverted signal s (-t) .
摘要:
Procédé de caractérisation ultrasonore d'un milieu comprenant une étape de génération d'une série d'ondes ultrasonores incidentes, une étape de génération d'une matrice de réflexion expérimentale R ui (t) définie entre la base d'émission ( i ) en entrée et une base de réception ( u ) en sortie, une étape de détermination d'une matrice de réflexion focalisée RFoc(r in , r out , δt) du milieu entre un transducteur virtuel d'entrée (TV in ) calculé à partir d'une focalisation en entrée de la matrice de réflexion expérimentale et un transducteur virtuel de sortie (TV out ) calculé à partir d'une focalisation en sortie de la matrice de réflexion expérimentale, les réponses du transducteur de virtuel de sortie (TV out ) étant prises à un instant temporel décalé d'un délai additionnel δt par rapport à un instant temporel des réponses du transducteur virtuel d'entrée (TV in ).
摘要:
A wave shaping device which comprises a tunable impedance surface and a controller connected to the surface in order to control its impedance. The shaping device further comprises a transmission module for receiving a pilot signal used to control the impedance of the surface.
摘要:
A method for mapping fibrous media by ultrasound propagation from a set (2) of transducers, which involves emitting a plurality of unfocused incident waves having different wave fronts, capturing the signals reverberated by the medium to each transducer, determining coherent signals corresponding respectively, for each transducer, to the contributions coming from various virtual focal points in the medium, then determining the orientation of the fibres by comparing the spatial coherence between said coherent signals, in a plurality of directions.
摘要:
A system for illuminating an object with a wave or for imaging an object (1) with a wave comprises a lens (10), a plurality of transducers (20) and a control unit (30) connected to the plurality of transducers. The lens comprises a plurality of resonator elements (12) incorporated inside a medium (11) and is able to convert a near field wave of the lens to a far field wave, or reciprocally. The resonator elements are at a sub wavelength distance from each others. The control unit provides signals to the transducers so that a plurality of points on the object are illuminated as desired, or obtains signals from the transducers to build an image of a plurality of points of the object. The points are at sub wavelength distance from each others.