Siemens Aktiengesellschaft

Roland Dill

Jurgen Machui

Werner Ruile

Brian Lewis

A filter operating with acoustical surface waves includes two acoustical paths each having one unidirectional input transducer, one unidirectional output transducer, and a reflector structure disposed between the input and output transducers. The input transducers in the acoustical paths are structurally identical, the output transducers in the acoustical paths are structurally identical, and the input and output transducers in each of the acoustical paths are spaced apart by the same distance. One of the input transducers or the output transducers are electrically connected in phase opposition, and the other of the input transducers or the output transducers are electrically connected in phase. The reflector structures in the two acoustical paths have substantially the same reflection performance, the reflector structure in one of the acoustical paths is shorter than the reflector structure in the other of the acoustical paths by .lambda./2, the reflector structures in the two acoustical paths are disposed centrally between the input and output transducers, and .lambda. is a wavelength at a mean frequency of the filter.

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Munchen, Germany

Roland Dill