Surface acoustic wave (SAW) filter with improved spacing between input and output interdigital transducers
AssigneeMitsubishi Denki Kabushiki Kaisha
InventorKoji Murai
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Abstract
A SAW filter is disclosed which includes two reflectors and a group of interdigital transducers (IDTs) located therebetween on a piezoelectric substrate, wherein the IDTs comprises at least four input IDTs and output IDTs alternatively aligned on the substrate in a SAW propagation direction to increase an transducer efficiency between an electronic signal and SAWs. Further, a distance between the center lines of the end electrode fingers of the adjacent input and output IDTs are set to be in a range from 0.625 .lambda. to 1.25 .lambda. (.lambda.: wave length of SAW) to establish input and output impedances of the SAW filter.
Claims15
A surface acoustic wave (SAW) filter comprising:
- a piezoelectric substrate;
- at least four input and output interdigital transducers (IDTs) alternately aligned on said substrate in a SAW propagation direction and being respectively connected to input and output terminals of said SAW filter;
- and
- two reflectors positioned at the opposite sides of said IDTs on said substrate, wherein a distance between center lines of electrode fingers at the inner ends of the adjacent input and output IDTs is set to be within a range from 0.625 .lambda. to 1.25 .lambda., where .lambda. denotes a wave length of a resonant frequency of said SAW filter.
Dependencies are inferred from the claim text.