Balanced saw filter
AssigneeMurata Manufacturing Co., Ltd.
InventorYuichi TAKAMINE
Life of this patent
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Abstract
In a balanced SAW filter, a third IDT of a first SAW filter element includes first and second IDT segments, and similarly, an eighth IDT of a second SAW filter element includes first and second IDT segments. A first IDT, the first IDT segment, the second IDT segment, and a fifth IDT included in the first SAW filter element are respectively connected to a sixth IDT, the first IDT segment, the second IDT segment, and a tenth IDT segment included in the second SAW filter element by first to fourth wiring lines. The phase of electric signals transmitted through the first and third wiring lines differs from the phase of electric signals transmitted through the second and fourth wiring lines by 180°.
Claims7
A balanced SAW filter having an unbalanced terminal and first and second balanced terminals, the balanced SAW filter comprising:
- a piezoelectric substrate;
- a first longitudinally-coupled-resonator SAW filter element including first to fifth IDTs arranged on the piezoelectric substrate in a propagation direction of surface acoustic waves, the second and fourth IDTs being connected to the unbalanced terminal, the third IDT in the center having a pair of bus bars, one of the bus bars being divided such that the third IDT includes first and second IDT segments;
- a second longitudinally-coupled-resonator SAW filter element including sixth to tenth IDTs arranged on the piezoelectric substrate in the propagation direction of surface acoustic waves, the seventh and ninth IDTs being respectively connected to the first and second balanced terminals, the eighth IDT in the center having a pair of bus bars, one of the bus bars being divided such that the eighth IDT is comprised of first and second IDT segments;
- a first wiring line connecting the first IDT to the sixth IDT;
- a second wiring line connecting the first IDT segment of the third IDT to the first IDT segment of the eighth IDT;
- a third wiring line connecting the second IDT segment of the third IDT to the second IDT segment of the eighth IDT;
- and
- a fourth wiring line connecting the fifth IDT to the tenth IDT;
- wherein
- the first to tenth IDTs are arranged such that the phase of electric signals transmitted through the first and third wiring lines differs from the phase of electric signals transmitted through the second and fourth wiring lines by 180°.
Dependencies are inferred from the claim text.