Transducer for surface wave filters with an asymmetrical transfer function
AssigneeThomson-CSF
InventorsJean Michel Autran, Bernard Epsztein
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Abstract
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.
Claims4
A transducer for a surface wave filter having an asymmetrical transfer function comprising two pairs of interdigital combs or electrodes disposed side by side on the same piezoelectric substrate to transmit acoustic waves along two parallel channels, these two pairs of combs having transfer functions which are symmetrical (Ts) and antisymmetrical (Ta), respectively, in relation to a common central frequency (Fo);
- said combs being staggered by one quarter of the acoustic wavelength in the direction of propagation of the waves so that the acoustic waves transmitted by the pair of combs with the antisymmetrical transfer function are advanced by .pi./2 relative to the waves transmitted by the other pair of combs.
Dependencies are inferred from the claim text.