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US 4,303,897 AGranted
Crystal filter structure for realizing a ladder filter
AssigneeTelefonaktiebolaget L M Ericsson
InventorHorst G. Augst
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AssigneeTelefonaktiebolaget L M Ericsson
InventorHorst G. Augst
Estimating the term…
The invention relates to a crystal filter structure of the polylithic type or built of discrete filter resonators for realizing a ladder filter with a number of L-links. Each link consists of two resonators (21) integrated on a quartz crystal plate (21) and weakly acoustically connected to form a quartz crystal element. The quartz crystal element are alternately arranged and fastened on opposite sides of a substrate plate, the resonators on different crystal elements are galvanically connected through metallic layers at the one of the longitudinal edges of the substrate plate and the intermediate edge surface. A common ground connection for all links is formed of metallic layers at the second longitudinal edge surface of the substrate plate. The connections of the "hot" electrodes are suitably turned towards the substrate plate and the input and the output of the filter are arranged on the opposite short sides of the substrate plate.
A crystal filter structure for realizing a ladder filter having at least three L-links connected in cascade between an input terminal and an output terminal comprising a plate-like substrate, a quartz plate for each L-link, each quartz plate including two electrode means for defining first and second quartz resonators, means for mounting at least a first of said quartz plates on one side of said substrate, means for mounting at least a second and a third of said quartz plates on the other side of said substrate, means for connecting the input terminal in parallel to one of the electrode means of the first and second quartz resonators on said first quartz plate, interside connecting means for connecting the other electrode means of the second quartz resonator of said first quartz plate in parallel to one of the electrode means of the first and second quartz resonators of said second quartz plate, intraside connecting means for connecting the other electrode means of the second quartz resonator of said second quartz plate in parallel to one of the electrode means of the first and second quartz resonators of said third quartz plate, output connecting means for connecting the other electrode means of the second quartz resonator of said third quartz plate to the output terminal, and common connecting means for commonly connecting the other electrode means of the first quartz resonators of said three quartz plates in common to a reference potential.
Dependencies are inferred from the claim text.