Dispersive delay lines operating in the shear mode

Claim 1

Dispersive delay line with an approximately linear time delay variation versus frequency over a large relative bandwidth and operation based on surface wave diffraction by periodic gratings, said line comprising : a propagation medium body 2 with parallel, plane faces 31,32 and a thickness d larger than the wavelength lambda of therein radiated elastic wave ; input and output elastic wave coupling means 1 ; 11,12, . . . input and output elastic wave type transducers 41, 42 located between said coupling means and at least one face of said medium and each comprising a plurality of rectilinear, co-planar, parallel grating elements presenting a periodic discontinuity in a corrugated pattern with an uniform corrugation pitch a forming a diffraction grating, one said grating element upon excitation generating an input surface wave, or ''''lateral wave,'''' and forming a bulk wave transducer 41 to propagate an elastic wave governed by a phase condition defined by the relationship phi n (2 pi f)/(C2) mna wherein n is the order number of the grating elements , C2 is the radiated wave propagation velocity in the said medium 2 , f is the received wave frequency and m is a parameter number, greater than one, depending on applied wave angle of incidence (sin Alpha 1) and the wave velocity ratio (C2/C1) and chosen in accordance with the desired time delay ( Delta t) and the wave frequency variations, said input diffraction grating 41 radiating a shear-bulk wave having a direction of oscillation parallel to said grating elements and an angle of emergence Alpha 2 in said medium dependent on wave frequency in accordance with the relation sin Alpha 2 m - p (C2)/(af) wherein p is a positive integer representing the diffraction order of the radiated wave energy, said wave energy being propagated through the medium irradiating the bulk-surface wave transducer output grating 42 at the same angle of incidence as the emergence angle Alpha 2 .