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 filter includes: a series-arm circuit; a first parallel-arm circuit connected to a ground and a node; and a second parallel-arm circuit connected to the ground and a node. The first parallel-arm circuit includes a parallel-arm resonator, and a first switch circuit. The second parallel-arm circuit includes a parallel-arm resonator, and a second switch circuit. The first switch circuit includes a first switch. The second switch circuit includes a second switch. A voltage across the first switch is lower than a voltage across the second switch. A stack count of the first switch is lower than a stack count of the second switch.

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 connected on a path connecting an input/output terminal and an input/output terminal, and first and second parallel-arm resonators connected between the same node on the path and ground. A resonant frequency of the first parallel-arm resonator is lower than a resonant frequency of the second parallel-arm resonator, and an anti-resonant frequency of the first parallel-arm resonator is lower than an anti-resonant frequency of the second parallel-arm resonator. The first parallel-arm resonator is defined by an acoustic wave resonator, and includes an IDT electrode that excites an acoustic wave, and a reflector that reflects the acoustic wave excited by the IDT electrode. A pitch between the IDT electrode and the reflector is about 0.42? or more and less than about 0.50?.

Abstract: A filter includes a parallel arm resonator and an interdigital capacitor. The parallel arm resonator has an IDT electrode defined by first electrode fingers. The interdigital capacitor is defined by second electrode fingers and is connected to the parallel arm resonator. The electrode finger pitch of the second electrode fingers is smaller than the electrode finger pitch of the first electrode fingers. The film thickness of the second electrode fingers is smaller than the film thickness of the first electrode fingers. A self-resonant frequency of the interdigital capacitor is higher than a pass band of the filter.

Abstract: A filter includes a longitudinally coupled resonator device, a parallel arm resonator, and a variable frequency circuit. The parallel arm resonator is connected between a ground and a node provided on a path connecting input-output terminals. The variable frequency circuit is connected to the first parallel arm resonator. The longitudinally coupled resonator device includes three or more odd-number IDT electrodes, an odd-numbered IDT terminal, and an even-numbered IDT terminal. The even-numbered IDT terminal is a first signal terminal connected to at least one IDT electrode located at an even-numbered position from an edge of an arrangement order of the plural IDT electrodes. The odd-numbered IDT terminal is a second signal terminal connected to two or more IDT electrodes located at odd-numbered positions from the edge. The longitudinally coupled resonator device is disposed so that the even-numbered IDT terminal is connected to the node.

Abstract: A filter includes a series arm circuit connected between an input-output terminal and an input-output terminal and a parallel arm circuit connected between a ground and a node. The parallel arm circuit includes a first circuit and a second circuit. The first circuit has a parallel arm resonator. The second circuit is connected in parallel with the first circuit and has a parallel arm resonator. At least one of the first and second circuits includes a variable frequency circuit. The variable frequency circuit is connected in series with the parallel arm resonator or the parallel arm resonator included in the corresponding one of the first and second circuits. The variable frequency circuit has an impedance element and a switch connected in parallel with each other. The parallel arm resonator has a resonant frequency different from the parallel arm resonator and an anti-resonant frequency different from the parallel arm resonator.

Abstract: A filter module (20) includes a filter circuit (22) that includes switches (221SW and 224SW), a pass band of the filter circuit (22) being switched in accordance with switching between ON and OFF of the switches (221SW and 224SW); and an impedance matching circuit (21) that is disposed in at least one of a preceding stage and a subsequent stage of the filter circuit (22) and that includes a switch (212SW), an element value for achieving impedance matching being switched in the impedance matching circuit (21) in accordance with switching between ON and OFF of the switch (212SW). The switches (221SW and 224SW) and the switch (212SW) synchronize with each other regarding timing of switching between ON and OFF.

Abstract: The acoustic wave filter (10A) includes a parallel-arm resonant circuit (12p). The parallel-arm resonant circuit (12p) includes a parallel-arm resonator (p1) and a frequency variable circuit (72p) that are connected in parallel. The frequency variable circuit (72p) includes a parallel-arm resonator (p2) that has a resonant frequency higher than that of the parallel-arm resonator (p1) and a switch (SW1) element. A frequency difference between a resonant frequency on a higher frequency side of the parallel-arm resonant circuit (12p) in a case where the switch (SW1) is OFF and a resonant frequency on a higher frequency side of the parallel-arm resonant circuit (12p) in a case where the switch (SW1) is ON is equal to or more than a frequency difference between a low frequency end frequency of the second attenuation band and a low frequency end frequency of the first attenuation band.

Abstract: A filter includes a series-arm resonator connected to a path connecting input/output terminals, and first and second parallel-arm resonators 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. The second parallel-arm resonator includes an IDT electrode that excites an acoustic wave, and does not include a reflector.

Abstract: A filter (10) includes a series arm circuit (11) and a parallel arm circuit (12). The parallel arm circuit (12) includes a parallel arm resonator (p1), a variable frequency circuit (12T), and a parallel arm resonator (p2) connected in parallel with a circuit in which the parallel arm resonator (p1) and the variable frequency circuit (12T) are connected in series. The variable frequency circuit (12T) includes a parallel arm resonator (p3) and a switch (SW) connected in parallel with the parallel arm resonator (p3), and is configured to change frequencies of a pass band and a frequency of an attenuation pole by switching between an on state and off state of the switch (SW). A resonant frequency and anti-resonant frequency of the parallel arm resonator (p1) are respectively different from a resonant frequency and anti-resonant frequency of the parallel arm resonator (p2).

Abstract: A filter (10) has a first passband and a second passband on a higher frequency side than the first passband and includes a series arm circuit (11) and a parallel arm circuit (12), wherein the parallel arm circuit (12) includes a parallel arm resonator (p1) connected between a node (x1) and ground and having a resonant frequency frp located between a first passband and a second passband, an inductor (L1) connected between the node (x1) and the ground, and an inductor (L2) connected between the node (x1) and the ground and connected in series to the parallel arm resonator (p1), and a circuit in which the parallel arm resonator (p1) and the inductor (L2) are connected in series is connected in parallel to the inductor (L1).

Abstract: A multiplexer includes first and second filters connected to a common terminal. The second filter has a pass band on a higher frequency side with respect to a pass band of the first filter. The first filter includes a series arm circuit, and a parallel arm circuit having a resonant frequency on a lower frequency side with respect to a frequency at a low frequency end of a pass band of the first filter, and the series arm circuit includes a series arm resonator having a resonant frequency in the pass band of the first filter and a series arm resonator that is electrically connected in parallel to the series arm resonator and that has a resonant frequency on a higher frequency side with respect to a frequency at a high frequency end of the pass band of the first filter.

Abstract: A radio-frequency filter (10) includes a series arm circuit (11) and a parallel arm circuit (12). The series arm circuit (11) includes a series arm resonator (s1a) and a variable frequency circuit (11b) connected in parallel with the series arm resonator (s1a). The variable frequency circuit (11b) includes a series arm resonator (s1b) and a switch (SWb) connected in series with the series arm resonator (s1b). The variable frequency circuit (11b) is configured to change at least one of a resonant frequency that provides a pass band of the radio-frequency filter (10) and an anti-resonant frequency that provides an attenuation pole of the radio-frequency filter (10). A resonant frequency of the series arm resonator (s1b) is different from a resonant frequency of the series arm resonator (s1a).

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: A radio-frequency filter (10) includes a series arm circuit (11) and a parallel arm circuit (12). The series arm circuit (11) is disposed on a path connecting an input/output terminal (11m) and an input/output terminal (11n). The parallel arm circuit (12) is connected to a ground and to a node (x1) on the path. The series arm circuit (11) includes a series connecting circuit (11e) and a first variable frequency circuit (11a). The series connecting circuit (11e) includes a series arm resonator (S1) and a capacitor (C1). The first variable frequency circuit (11a) is connected in parallel with the series connecting circuit (11e) and varies the anti-resonant frequency of the series arm circuit (11). The first variable frequency circuit (11a) includes a capacitor (C2) and a switch (SW1) connected in series with each other. The series arm resonator (s1) and the capacitor (C1) are connected in series with each other.

Abstract: A radio-frequency filter (10) includes a series arm resonator (s1) connected between input/output terminals (11m and 11n) and parallel arm circuits (110 and 120) connected to a node (x1) and a ground. The parallel arm circuit (110) includes a parallel arm resonator (p1) and a variable frequency circuit (110A) connected in series with each other between the node (x1) and a ground. The variable frequency circuit (110A) changes the resonant frequency of the parallel arm circuit (110). The variable frequency circuit (110A) is connected in series with the parallel arm resonator (p1) and includes a capacitor (C1) and a switch (SW1) connected in parallel with each other. The parallel arm circuit (120) includes a capacitor (C2) and a switch (SW2) connected in series with each other between the node (x1) and a ground.

Abstract: A variable filter (10) includes a parallel arm resonance circuit and a serial arm resonance circuit, the parallel arm resonance circuit includes a parallel arm resonator (p1) having an IDT electrode (121) and a frequency variable circuit (11) connected to the parallel arm resonator (p1), the frequency variable circuit (11) includes a capacitance element (C1) and a switch (SW), the variable filter (10) further includes a capacitance element (C2) connected between a serial arm and ground, the IDT electrode (121), an IDT wiring connected to the IDT electrode (121), and a capacitance wiring connected to the capacitance element (C1) are formed on the same substrate, a wiring (141 or 144) of the capacitance wirings and a wiring (143) of the IDT wirings intersect with each other, and the capacitance element (C2) is configured of the capacitance wiring and the IDT wiring in the intersection region.

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: 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.