Balanced type surface acoustic wave filter
AssigneeMurata Manufacturing Co., Ltd.
InventorMasakazu Tani
Life of this patent
Estimating the term…
Abstract
In a balanced type surface acoustic wave filter, a first longitudinally coupled resonator-type surface acoustic wave filter portion connected to an unbalanced input terminal and a second longitudinally coupled resonator-type surface acoustic wave filter portion connected to first and second balanced input terminals are two-stage cascade connected. In the first longitudinally coupled resonator-type surface acoustic wave filter portion, in a portion in which first and second IDTs are adjacent to each other and a portion in which second and third IDTs are adjacent to each other, weighting is performed on a plurality of electrode fingers including the outermost electrode finger closest to the adjacent IDT, in at least one of the adjacent IDTs.
Claims12
A balanced-type surface acoustic wave filter with a balanced-to-unbalanced conversion function including an unbalanced signal terminal and first and second balanced signal terminals, the balanced-type surface acoustic filter comprising:
- a piezoelectric substrate;
- a first longitudinally coupled resonator-type surface acoustic wave filter portion having first to third IDTs disposed along a propagation direction of a surface wave on the piezoelectric substrate, a middle second IDT of the first to third IDTs being connected to the unbalanced signal terminal;
- and
- a second longitudinally coupled resonator-type surface acoustic wave filter portion having fourth to sixth IDTs disposed along the propagation direction of the surface wave on the piezoelectric substrate, the fourth IDT connected to the first IDT, and the fifth IDT connected to the first and second balanced signal terminals;
- wherein
- an electric signal passing through a signal line connecting the first IDT and the fourth IDT is about 180 degrees different in phase from an electric signal passing through a signal line connecting the third IDT and the sixth IDT;
- and
- in the first longitudinally coupled resonator-type surface acoustic wave filter portion, in at least one of the portion where the first and second IDTs are adjacent to each other and the portion where the second and third IDTs are adjacent to each other, in at least one of the adjacent IDTs, weighting is provided on a plurality of electrode fingers including an outermost electrode finger which is the closest to the adjacent IDT.
Dependencies are inferred from the claim text.