Abstract: A multiplexer (1) includes a plurality of filters connected to a common terminal (110). The multiplexer (1) includes: a low-frequency filter (11L) that is formed of at least one surface acoustic wave resonator arranged between the common terminal (110) and the input/output terminal (120) and has a first pass band; a high-frequency filter (12H) that is connected between the common terminal (110) and the input/output terminal (130) and has a second pass band located at a higher frequency than the first pass band; and a capacitor (CB1) that is serially arranged in a connection path between the common terminal (110) and the low-frequency filter (11L). The Q value of the capacitor (CB1) in the second pass band is higher than the Q value in the second pass band of a capacitance obtained by treating the at least one surface acoustic wave resonator of the low-frequency filter (11L) as a capacitance.

Abstract: A variable filter includes a serial arm resonator and a parallel arm resonance circuit, the parallel arm resonance circuit includes a parallel arm resonator and a capacitance element connected to the parallel arm resonator, the serial arm resonator and the parallel arm resonator respectively include IDT electrodes each formed of a plurality of electrode fingers formed on a substrate, and a film thickness of the plurality of electrode fingers of the parallel arm resonator is larger than a film thickness of the plurality of electrode fingers of the serial arm resonator.

Abstract: An acoustic wave filter includes series arm resonators, and a parallel arm resonator provided in a second path connecting a ground and a node connecting the series arm resonators. Each of the series arm resonators includes a piezoelectric body and an interdigital transducer electrode. One of the series arm resonators includes a second adjusting film that adjusts Ksaw. An anti-resonant frequency of the other one of the series arm resonators is higher than an anti-resonant frequency of the one of series arm resonators. An adjusting film that adjusts Ksaw is not provided in the other one of series arm resonators, or when a first adjusting film that adjusts Ksaw is provided in the other one of the series arm resonators, the first adjusting film is thinner than the second adjusting film.

Abstract: A multiplexer (1) includes a plurality of filters connected to a common terminal (110). The multiplexer (1) includes: a low-frequency filter (11L) that is formed of at least one surface acoustic wave resonator arranged between the common terminal (110) and the input/output terminal (120) and has a first pass band; a high-frequency filter (12H) that is connected between the common terminal (110) and the input/output terminal (130) and has a second pass band located at a higher frequency than the first pass band; and a capacitor (CB1) that is serially arranged in a connection path between the common terminal (110) and the low-frequency filter (11L). The Q value of the capacitor (CB1) in the second pass band is higher than the Q value in the second pass band of a capacitance obtained by treating the at least one surface acoustic wave resonator of the low-frequency filter (11L) as a capacitance.

Abstract: A filter includes a series arm resonator, a first parallel arm resonance circuit, and a second parallel arm resonance circuit. The first parallel arm resonance circuit includes: a first parallel arm resonator connected to a first node; a first capacitor and a first switch connected together in parallel and connected in series with the first parallel arm resonator; and a first inductor provided on a path connecting the node and ground to each other via the first switch. The second parallel arm resonance circuit includes: a second parallel arm resonator connected to a second node; a second capacitor and a second switch connected together in parallel and connected in series with the second parallel arm resonator; and a second inductor provided on a path connecting the second node and ground to each other via the second switch. The first and second inductor have different inductance values.

Abstract: A filter includes a series arm resonator, a first parallel arm resonance circuit and a second parallel arm resonance circuit. The each of the first parallel arm resonance circuit and the second parallel arm resonance circuit includes: a parallel arm resonator that is connected to a node; a pair of elements consisting of a capacitor and a switch, which are connected in parallel with each other, that is connected in series with the parallel arm resonator; and an inductor that is provided on a path that connects the node and ground to each other via the switch. The inductance value of the inductor of the first parallel arm resonance circuit and the inductance value of the inductor of the second parallel arm resonance circuit are substantially equal to each other.

Abstract: A multiplexer (1) includes a plurality of filters connected to a common terminal (110). The multiplexer (1) includes: a low-frequency filter (11L) that is formed of at least one surface acoustic wave resonator arranged between the common terminal (110) and the input/output terminal (120) and has a first pass band; a high-frequency filter (12H) that is connected between the common terminal (110) and the input/output terminal (130) and has a second pass band located at a higher frequency than the first pass band; and a capacitor (CB1) that is serially arranged in a connection path between the common terminal (110) and the low-frequency filter (11L). The Q value of the capacitor (CB1) in the second pass band is higher than the Q value in the second pass band of a capacitance obtained by treating the at least one surface acoustic wave resonator of the low-frequency filter (11L) as a capacitance.

Abstract: A filter includes: a series-arm circuit; a first parallel-arm circuit connected to a node and a ground; and a second parallel-arm circuit connected to a node and the ground. The first parallel-arm circuit includes a first parallel-arm resonator, and a first switch circuit connected in series to the first parallel-arm resonator. The second parallel-arm circuit includes a second parallel-arm resonator, and a second switch circuit connected in series to the second parallel-arm resonator. The first switch circuit includes a first switch element that includes one or more transistors. The second switch circuit includes a second switch element that includes one or more transistors. A gate width of each of the one or more transistors included in the first switch element is greater than a gate width of at least one of the one or more transistors included in the second switch element.

Abstract: A multiplexer includes a first filter located between a common terminal and a first terminal to pass a signal in a first passband, and a second filter located between the common terminal and a second terminal to pass a signal in a second passband. A first series arm circuit included in the first filter includes a first series arm resonator and a second series arm resonator. The first series arm circuit is connected to the common terminal not through a circuit including an elastic wave resonator and a connecting point of the circuit. The first series arm circuit has a first antiresonance frequency and a second antiresonance frequency higher than the first antiresonance frequency. The second antiresonance frequency is higher than a higher edge of the first passband. The first antiresonance frequency is at or lower than a higher edge of the second passband.

Abstract: A filter includes: a series-arm resonator; and a parallel-arm resonator. The series-arm resonator and the parallel-arm resonator each include: an interdigital transducer (IDT) electrode formed on a substrate and including a plurality of electrode fingers; and a protective film. The protective film included in the parallel-arm resonator is thinner than the protective film included in the series-arm resonator. The parallel-arm resonator has a first fractional bandwidth ((the higher-order resonance frequency?the resonant frequency)/the resonant frequency) greater than the first fractional bandwidth of the series-arm resonator. The parallel-arm resonator has a second fractional bandwidth ((the higher-order antiresonant frequency?the antiresonant frequency)/the antiresonant frequency) greater than the second fractional bandwidth of the series-arm resonator.

Abstract: A filter includes a first resonant circuit having one or more first resonant frequencies, a second resonant circuit having one or more second resonant frequencies different from the first resonant frequency, and a switch connected to the first resonant circuit and the second resonant circuit. The switch switches between a first state in which a radio-frequency signal of the first resonant frequency flows from an IN terminal to an OUT terminal via the first resonant circuit and a radio-frequency signal of the second resonant frequency flows from the IN terminal to ground via the second resonant circuit and a second state in which a radio-frequency signal of the first resonant frequency flows from the IN terminal to ground via the first resonant circuit and a radio-frequency signal of the second resonant frequency flows from the IN terminal to the OUT terminal via the second resonant circuit.

Abstract: A filter includes a series arm resonant circuit connected between input/output terminals, and a parallel arm resonant circuit connected between a node on a path connecting the input/output terminals and ground. The series arm resonant circuit includes a series arm resonator having a band width ratio wider than the band width ratio of the parallel arm resonant circuit and a capacitor connected to the series arm resonator.

Abstract: An acoustic wave filter device includes a ground connection terminal connected to an external ground electrode, a serial arm resonator, a first parallel arm circuit connected to a first node of the serial arm resonator, the first node being positioned closer to an input/output terminal, and to the ground connection terminal, and a second parallel arm circuit connected to a second node of the serial arm resonator, the second node being positioned closer to an input/output terminal, and to the ground connection terminal. The first parallel arm circuit includes a parallel arm resonator having a resonant frequency higher than a center frequency of a filter pass band, and a frequency varying circuit connected to the parallel arm resonator and the ground connection terminal. The second parallel arm circuit includes a parallel arm resonator having a resonant frequency higher than the center frequency of the filter pass band.

Abstract: A filter device according to an embodiment of the present disclosure includes a first filter and a second filter that are connected in parallel between a first terminal and a second terminal. The first filter includes multiple series arm resonators. The series arm resonators are disposed in series in a path from the first terminal via the first filter to the second terminal. The series arm resonators include a first series arm resonator and a second series arm resonator. Under a condition that a value obtained by dividing a difference between an antiresonance frequency and a resonance frequency of each series arm resonator by the resonance frequency is defined as a fractional bandwidth, a first fractional bandwidth of the first series arm resonator is different from a second fractional bandwidth of the second series arm resonator.

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.

Abstract: A radio-frequency filter includes a first series-arm circuit and a second series-arm circuit that is on a circuit path closer to the output terminal than the first series-arm circuit. A first parallel-arm circuit is connected to a ground and a node on the path between the first series-arm circuit and the second series-arm circuit. The first series-arm circuit includes a first series-arm resonator, and a first switch element, the first switch element including first semiconductor elements arranged in series. The second series-arm circuit includes a second series-arm resonator, and a second switch element, the second switch element including at least one second semiconductor element. A first stack number being higher than a second stack number, the first stack number being a number of the first semiconductor elements and the second stack number being a number of the one or more second semiconductor elements.

Abstract: A multiplexer includes a common terminal, a first terminal, a second terminal, and a third terminal, a first filter, a second filter, and a third filter. With a frequency f3 being defined as M×f1±N×f2 or M×f2±N×f1, M and N being natural numbers, f1 being a frequency included in a first passband of the first filter and f2 being a frequency included in a second passband of the second filter, at least a part of a range of frequency f3 overlaps a third passband of the third filter. No acoustic wave resonator is connected between the common terminal and a first parallel arm resonance circuit. A combined capacitance of the first parallel arm resonance circuit is higher than a minimum value of a combined capacitance of each of at least one first serial arm resonance circuit.

Abstract: A filter (11) includes a series-arm circuit (10) connected between an input/output terminal (11m) and an input/output terminal (11n); and a parallel-arm circuit (20) connected between a ground and a path that connects the input/output terminal (11m) and the input/output terminal (11n). One circuit among the series-arm circuit (10) and the parallel-arm circuit (20) is constituted by a parallel-arm resonator (p1) and a parallel-arm resonator (p2) that are connected in parallel to each other and that are connected to a node (x1) on the path. The parallel-arm resonators (p1) and (p2) form a pass band, together with another circuit among the series-arm circuit (10) and the parallel-arm circuit (20). The parallel-arm resonator (p2) has a resonant frequency lower than a resonant frequency of the parallel-arm resonator (p1) and has an impedance higher than an impedance of the parallel-arm resonator (p1).

Abstract: A multiplexer includes a common terminal, a first terminal, a second terminal, and a third terminal, a first filter, a second filter, and a third filter. With a frequency f3 being defined as M×f1±N×f2 or M×f2±N×f1, M and N being natural numbers, f1 being a frequency included in a first passband of the first filter and f2 being a frequency included in a second passband of the second filter, at least a part of a range of frequency f3 overlaps a third passband of the third filter. No acoustic wave resonator is connected between the common terminal and a first parallel arm resonance circuit. A fractional bandwidth of the first parallel arm resonance circuit is smaller than a maximum value of a fractional bandwidth of each of at least one serial arm resonance circuit.

Abstract: A filter includes a series-arm resonator connected on a path connecting input/output terminals, and first and second parallel-arm resonators that are connected between the same node on the path and ground. A resonant frequency of the second parallel-arm resonator is higher than a resonant frequency of the first parallel-arm resonator, and an anti-resonant frequency of the second parallel-arm resonator is higher than an anti-resonant frequency of the first parallel-arm resonator. Each of the first and second parallel-arm resonators is defined by an acoustic wave resonator including an IDT electrode. The IDT electrode in the second parallel-arm resonator has a lower aspect ratio than the IDT electrode in the first parallel-arm resonator, where the aspect ratio is a ratio of an overlap width of electrode fingers to the number of pairs of electrode fingers.