Filter device, radio-frequency front-end circuit, and communication apparatus
AssigneeMurata Manufacturing Co., Ltd.
InventorKoji Nosaka
Life of this patent
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Abstract
A filter device includes a first filter and a second filter. The first filter and the second filter are disposed in parallel between a first terminal and a second terminal. A first passband of the filter device includes at least part of a second passband of the first filter. The first passband includes at least part of a third passband of the second filter. The second passband is narrower than the first passband. The third passband is narrower than the first passband. The third passband has a center frequency higher than a center frequency of the second passband. The first filter includes multiple elastic wave resonators and a first capacitive element. The first capacitive element is connected in parallel with the first elastic wave resonator.
Claims17
A filter device having a passband, the filter device comprising:
- a first filter and a second filter connected in parallel with each other between a first terminal and a second terminal,
- wherein the first and second filters are configured so that:
- the passband of the filter device includes at least part of a first passband of the first filter and at least part of a second passband of the second filter,
- the first passband and the second passband are both narrower than the passband of the filter device, and
- the second passband has a center frequency higher than a center frequency of the first passband,
- wherein the first filter includes:
- a plurality of elastic wave resonators, and
- a first capacitive element connected in parallel with a first elastic wave resonator included in the plurality of elastic wave resonators, and
- wherein the first and second filters are further configured so that:
- the first passband and the second passband do not overlap each other,
- the passband of the filter device is continuous,
- an insertion loss of the filter device in the passband of the filter device falls within a range from a minimum value of the insertion loss to a value obtained by adding 3 dB to the minimum value, and
- in a frequency band between the first passband and the second passband, the insertion loss of the filter device is smaller than an insertion loss of each of the first filter and the second filter.
A radio-frequency (RF) front-end circuit comprising:
- an amplifier circuit;
- and
- a filter device, the filter device including
- a first filter and a second filter connected in parallel with each other between a first terminal and a second terminal,
- wherein the first and second filters are configured so that:
- a passband of the filter device includes at least part of a first passband of the first filter and at least part of a second passband of the second filter,
- the first passband and the second passband are both narrower than the passband of the filter device, and
- the second passband has a center frequency higher than a center frequency of the first passband,
- wherein the first filter includes:
- a plurality of elastic wave resonators, and
- a first capacitive element connected in parallel with a first elastic wave resonator included in the plurality of elastic wave resonators, and
- wherein the first and second filters are further configured so that:
- the first passband and the second passband do not overlap each other,
- the passband of the filter device is continuous, and
- an insertion loss of the filter device in the passband of the filter device falls within a range from a minimum value of the insertion loss to a value obtained by adding 3 dB to the minimum value, and
- in a frequency band between the first passband and the second passband, the insertion loss of the filter device is smaller than an insertion loss of each of the first filter and the second filter;
- and
- wherein the amplifier circuit is electrically connected to the filter device.
Dependencies are inferred from the claim text.