Ladder-filter with edge reflection acoustic surface wave filter resonators

摘要

The filter (11) has a number of serially connected series arm resonators defining a serial arm of a ladder circuit arranged in a first integrated region (13). Each series arm resonator has an edge reflection acoustic surface wave resonator. A number of parallel arm resonators are connected between the serial arm and earth potential to define a parallel arm of the ladder circuit and which have an edge reflection acoustic surface wave resonator. A first group of at least two parallel arm resonators is arranged in a second integrated region (14) physically separate from the first integrated region so that the horizontal shear acoustic surface waves which are stimulated in a section of piezoelectric material in the first integrated region do not disturb those stimulated in the second region.