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US 12,756,378 B2Granted
Composite transversely-excited film bulk acoustic resonator circuits having a capacitor for improved rejection
AssigneeMurata Manufacturing Co., Ltd.
InventorKurt Raihn
Life of this patent
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Abstract
A filter circuit has a resonator circuit with a first acoustic resonator and a second acoustic resonator connected in series on a printed circuit board (PCB). The filter circuit also has a composite resonator circuit formed by a capacitor connected in parallel with the second acoustic resonator on the PCB. The capacitor is configured to improve a steepness of an upper bandpass edge of the filter circuit.
Claims20
A filter circuit comprising:
- a resonator circuit having a first acoustic resonator and a second acoustic resonator connected in series on a single chip;
- and
- a composite resonator circuit comprising a capacitor connected in parallel with the first acoustic resonator and the second acoustic resonator on the single chip,
- wherein each of the first and second acoustic resonators comprises:
- a substrate;
- a piezoelectric layer having a first portion supported by the substrate and a second portion that is over a cavity;
- and
- an interdigital transducer (IDT) on a surface of the piezoelectric layer, the IDT including interleaved fingers on the second portion of the piezoelectric layer that is over the cavity,
- wherein the first and second acoustic resonators have a substantially identical sized cavity, a substantially identical thickness and a substantially identical pitch of the interleaved fingers, and
- wherein the first and second acoustic resonators have a substantially same resonance frequency, anti-resonance frequency, and static capacitance.
7 more elements
A filter circuit comprising:
- a first acoustic resonator and a second acoustic resonator connected in series on a substrate and having respective transfer functions, wherein each of the first and second acoustic resonators includes an interdigital transducer (IDT) on a piezoelectric layer, such that interleaved fingers of the IDT are disposed on a diaphragm of the piezoelectric layer that is over a cavity;
- and
- a capacitor connected in parallel with the second acoustic resonator on the substrate,
- wherein the first and second acoustic resonators have a substantially identical sized cavity, a substantially identical thickness and a substantially identical pitch of the interleaved fingers, and
- wherein the first and second acoustic resonators have a substantially same resonance frequency, anti-resonance frequency, and static capacitance.
2 more elements
A filter circuit comprising:
- a first acoustic resonator and a second acoustic resonator connected in series on a substrate;
- a capacitor connected in parallel with the second acoustic resonator on the substrate;
- a plurality of series resonators connected in series between a first port and a second port, the plurality of series resonators including a first series resonator and a second series resonator connected at a node;
- and
- a plurality of shunt resonators including a first shunt resonator coupled between the node and a ground,
- wherein the second series resonator includes the first acoustic resonator and the second acoustic resonator, and
- wherein the first and second acoustic resonators have a substantially identical sized cavity, a substantially identical thickness and a substantially identical pitch of interleaved fingers of interdigital transducers (IDTs) of the first and second acoustic resonators.
4 more elements
Dependencies are inferred from the claim text.