Thomson-csf

Jean Michel Autran

Bernard Epsztein

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.

Transducer for surface wave filters with reduced diffraction

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.

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Paris, France

Jean Michel Autran