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US 2003/0164745 A1Published application
Surface acoustic wave filter
AssigneeMurata Manufacturing Co., Ltd.
InventorYuichi Takamine
Life of this patent
Estimating the term…
Abstract
A surface acoustic wave filter includes, on a piezoelectric substrate, longitudinally coupled resonator type surface acoustic wave filter sections, including interdigital transducers, each having a narrow-pitched electrode finger portion in an area where interdigital transducers are adjacent to each other, first surface acoustic wave resonators, between the surface acoustic wave filter sections and an input terminal, and second surface acoustic wave resonators between the surface acoustic wave filter sections and output terminals. The resonance point of the surface acoustic wave resonators falls within the passband of the surface acoustic wave filter sections, and the antiresonance point of the surface acoustic wave resonators is in the vicinity of the high frequency side of the passband.
Claims25
A surface acoustic wave filter comprising:
- a surface acoustic wave filter section including a piezoelectric substrate, at least two interdigital transducers arranged in a direction of propagation of a surface acoustic wave propagated on the piezoelectric substrate, wherein each of the at least two interdigital transducers includes a narrow-pitched electrode finger portion in which a pitch of electrode fingers in a portion of the interdigital transducer at an end of the interdigital transducer is narrower than that of electrode fingers in the remaining portions of the interdigital transducer at an area where the at least two interdigital transducers are adjacent to each other;
- and
- at least one surface acoustic wave resonator connected in series between the surface acoustic wave filter section and one of an input signal terminal and an output signal terminal;
- wherein
- the surface acoustic wave filter section is a threefold mode surface acoustic wave filter section of a longitudinally coupled resonator type, and an impedance of the surface acoustic wave filter section is capacitive in a resonance mode in the highest frequency region of three resonance modes thereof;
- the resonance point of the surface acoustic wave resonator is within a passband of the surface acoustic wave filter section, and the antiresonance point of the surface acoustic wave resonator is in the vicinity of the high frequency region of the passband of the surface acoustic wave filter section;
- and
- the surface acoustic wave resonator is arranged such that the impedance in the resonance mode positioned in the highest frequency region is close to an impedance matching point.
5 more elements
A surface acoustic wave filter comprising:
- a surface acoustic wave filter section including a piezoelectric substrate, at least two interdigital transducers arranged in a direction of propagation of a surface acoustic wave propagated on the piezoelectric substrate, and a reflector arranged in an area where the at least two interdigital transducers are adjacent to each other, the reflector having a plurality of electrode fingers having an electrode finger pitch different from an electrode finger pitch of the at least two interdigital transducers;
- and
- at least one surface acoustic wave resonator connected in series between the surface acoustic wave filter section and one of an input signal terminal and an output signal terminal;
- wherein
- the surface acoustic wave filter section is a threefold mode surface acoustic wave filter section of a longitudinally coupled resonator type, and an impedance of the surface acoustic wave filter section is capacitive in a resonance mode in the highest frequency region outside of three resonance modes;
- the resonance point of the surface acoustic wave resonator is positioned within a passband of the surface acoustic wave filter section, and the antiresonance point of the surface acoustic wave resonator is positioned in the vicinity of the high frequency region of the passband of the surface acoustic wave filter section;
- and
- the at least one surface acoustic wave resonator is arranged such that the impedance in the resonance mode in the highest frequency region is close to an impedance matching point.
5 more elements
A communication apparatus comprising a surface acoustic wave filter comprising:
- a surface acoustic wave filter section including a piezoelectric substrate, at least two interdigital transducers arranged in a direction of propagation of a surface acoustic wave propagated on the piezoelectric substrate, wherein each of the at least two interdigital transducers includes a narrow-pitched electrode finger portion in which a pitch of electrode fingers in a portion of the interdigital transducer at an end of the interdigital transducer is narrower than that of electrode fingers in the remaining portions of the interdigital transducer at an area where the at least two interdigital transducers are adjacent to each other;
- and
- at least one surface acoustic wave resonator connected in series between the surface acoustic wave filter section and one of an input signal terminal and an output signal terminal;
- wherein
- the surface acoustic wave filter section is a threefold mode surface acoustic wave filter section of a longitudinally coupled resonator type, and an impedance of the surface acoustic wave filter section is capacitive in a resonance mode in the highest frequency region of three resonance modes thereof;
- the resonance point of the surface acoustic wave resonator is within a passband of the surface acoustic wave filter section, and the antiresonance point of the surface acoustic wave resonator is in the vicinity of the high frequency region of the passband of the surface acoustic wave filter section;
- and
- the surface acoustic wave resonator is arranged such that the impedance in the resonance mode positioned in the highest frequency region is close to an impedance matching point.
5 more elements
A communication apparatus comprising a surface acoustic wave filter comprising:
- a surface acoustic wave filter section including a piezoelectric substrate, at least two interdigital transducers arranged in a direction of propagation of a surface acoustic wave propagated on the piezoelectric substrate, and a reflector arranged in an area where the at least two interdigital transducers are adjacent to each other, the reflector having a plurality of electrode fingers having an electrode finger pitch different from an electrode finger pitch of the at least two interdigital transducers;
- and
- at least one surface acoustic wave resonator connected in series between the surface acoustic wave filter section and one of an input signal terminal and an output signal terminal;
- wherein
- the surface acoustic wave filter section is a threefold mode surface acoustic wave filter section of a longitudinally coupled resonator type, and an impedance of the surface acoustic wave filter section is capacitive in a resonance mode in the highest frequency region outside of three resonance modes;
- the resonance point of the surface acoustic wave resonator is positioned within a passband of the surface acoustic wave filter section, and the antiresonance point of the surface acoustic wave resonator is positioned in the vicinity of the high frequency region of the passband of the surface acoustic wave filter section;
- and
- the at least one surface acoustic wave resonator is arranged such that the impedance in the resonance mode in the highest frequency region is close to an impedance matching point.
5 more elements
Dependencies are inferred from the claim text.