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US 4,325,037 AGranted
Acoustic wave filter
AssigneeSiemens Aktiengesellschaft
InventorsWolf E. Bulst, Hans Eschler
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AssigneeSiemens Aktiengesellschaft
InventorsWolf E. Bulst, Hans Eschler
Estimating the term…
An acoustic wave filter comprising a piezoelectric substrate body upon which at least two digital structures are formed and which comprise input and output transducers and form a selective wave reflective pair with at least one of the digital structures having a wide band amplitude characteristic F1 and at least one of the other digital structures having a narrower frequency band amplitude characteristic and wherein the center frequency f1 of the wider band F1 digital structure is displaced relative to the center frequency f2 of the digital structure which has a narrower frequency band F2 by a frequency of .DELTA..sub.f on either side of the center frequency f1 so that one of the zero locations f.sub.R1'2 of the distortion signal F.sub.R of interdigital reflections is placed close to the value of the center frequency f.sub.0 of the filter.
A piezoelectric substrate, a first interdigital structure (12) formed on a first surface of said substrate, having a mean frequency of f.sub.1 and frequency band width of F.sub.1, a second interdigital structure formed on a first surface of said substrate and longitudinally offset from said first interdigital structure and having a mean frequency of f.sub.2 and a frequency band width F.sub.2 which is narrower than the frequency band width of F.sub.1 of said first interdigital structure, said mean frequency f.sub.2 of said second interdigital structure offset by a frequency displacement .DELTA.f from the mean frequency of said first interdigital structure so that the amplitude characteristic F.sub.2 of said second interdigital structure has a mean frequency f.sub.2 which occurs at one half the distance from f.sub.1 to a zero of the amplitude characteristic of F.sub.1.
A wave filter comprising, a piezoelectric substrate, a first interdigital structure (11) formed on said substrate and having a relatively wider frequency bandpass response (F.sub.1), a second interdigital structure formed on said substrate and having a relatively narrow frequency bandpass response (F.sub.2), and the center frequency f.sub.2 of (F.sub.2) which is shifted .DELTA.f from the center frequency f.sub.1 of F.sub.1 but still falls in the response F.sub.1, so that reflections which cause distortions are eliminated.
A wave filter with a center frequency f.sub.0 comprising, a piezoelectric substrate, a first interdigital structure (11) formed on said substrate and having a relatively wider frequency response F.sub.1, and a mean frequency f.sub.1, a second interdigital structure formed on said substrate and having a relatively narrow frequency response F.sub.2, the mean frequency f.sub.2 of the narrow frequency response F.sub.2 digital structure (13;
Dependencies are inferred from the claim text.