Crystal filter structure for realizing a ladder filter

摘要

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.