SAW dispersive delay device

Claim 1

A SAW reflective array correlator utilizing metallic reflectors with positive and negative reflection coefficients comprising a substrate of 128° Y-X LiNbO 3 , an input and output periodic interdigital transducer on said substrate, a pair of coextensive reflective arrays on said substrate and aligned respectively with said transducers, said transducers and said arrays being of thin-film aluminum photo-etched on said substrate, said reflective arrays having a multiplicity of shorted reflectors and a multiplicity of open reflectors that are alternately interleaved with the shorted reflectors, the reflectors of each reflective array being inclined substantially 45° with respect to the transducer propagation direction and the x-axis of the 128° Y-X LiNbO 3 substrate, the periodicity of the reflectors varying along the length of each reflective array so that different frequencies are reflected at different locations along each array to thereby provide a different delay path, the periodicity variation being the same in the two arrays, the width of the shorted and open reflectors and the separation between the reflectors decreasing in a predetermined linear manner along the length of each reflective array for increasing frequencies to be reflected by the array, the spacing between said shorted reflectors being equal to λ/2 and between adjacent open and shorted reflectors being equal to λ/4 where λ corresponds to the SAW wavelength for the frequency associated with a given section of a reflective array, said shorted and open reflectors having a length that is substantially coextensive with the acoustic aperture of the input and output transducers.