A switch module includes a first terminal, first and second filters, and first and second switches. Impedance of the first filter for a signal in a stop band is capacitive. When the first switch is turned OFF, impedance of the first switch is capacitive, and impedance of the first filter seen from an end portion of the first switch connected to the first filter is not in a short state and impedance of the first filter seen from the first terminal is in an open state.

An acoustic wave device includes a piezoelectric substrate, interdigital transducer electrodes including a predetermined number of electrode fingers disposed on an upper surface of the substrate, and a dielectric material layer having a first portion and a second portion. The first portion is disposed on the upper surface of the substrate and between the interdigital transducer electrode fingers. The second portion is disposed above the interdigital transducer electrode fingers. The acoustic wave device further includes at least one thermally conductive bridge disposed within the dielectric material layer and contacting upper surfaces of at least two adjacent interdigital transducer electrode fingers to dissipate heat therefrom.

An acoustic wave device comprises a piezoelectric substrate, interdigital transducer electrodes having an electrode pitch λ.sub.0, and first and second reflector gratings disposed on opposite respective sides of the interdigital transducer electrodes in a propagation direction of a main acoustic wave through the acoustic wave device, the first reflector grating having a different electrode pitch λ.sub.1 than an electrode pitch λ.sub.2 of the second reflector grating to suppress ripples in a conductance curve of the acoustic wave device.

Embodiments of resonator circuits and modulating resonators and are described generally herein. One or more acoustic wave resonators may be coupled in series or parallel to generate tunable filters. One or more acoustic wave resonances may be modulated by one or more capacitors or tunable capacitors. One or more acoustic wave modules may also be switchable in a filter. Other embodiments may be described and claimed.

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 (C.sub.B1) 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 (C.sub.B1) 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.

An acoustic wave element includes an IDT electrode includes pluralities of electrode fingers, and reflector electrodes on the two sides of the IDT electrode. The IDT electrode includes a major part and at least one end part which is located between the major part and one of the reflector electrodes and is arranged along a direction of propagation of an acoustic wave together with the major part. the at least one end part includes a pitch of the plurality of electrode fingers substantially the same as a pitch of the plurality of electrode fingers in the major part, is electrically connected in parallel with respect to the major part, and is divided into two or more sections which are electrically connected in series with each other.

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 (C.sub.B1) 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 (C.sub.B1) 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.

A front-end module may include an acoustic wave filter with a first and second interdigital transducer electrode, and a low noise amplifier (LNA) that converts a differential input to a single-ended output with respect to ground. The first interdigital transducer electrode may be single-ended with a first input bus bar configured to receive an input signal and a second input bus bar connected to ground. The second interdigital transducer electrode may be differential with a first output bus bar connected to a first output terminal and a second output bus bar connected to a second output terminal. The LNA may have a differential input connected to the acoustic wave filter, a first input transistor that receives a first signal from the first output terminal of the acoustic wave filter, and a second input transistor that receives a second signal from the second output terminal of the acoustic wave filter.

A front-end module may include an acoustic wave filter with a first and second interdigital transducer electrode. The first interdigital transducer electrode may be single-ended with a first input bus bar that receives an input signal and a second input bus bar connected to ground. The second interdigital transducer electrode may be differential with a first output bus bar connected to a first output terminal and a second output bus bar connected to a second output terminal. The front-end module may include a low noise amplifier (LNA) that outputs a differential signal via a differential output and has a differential input connected to the acoustic wave filter. The LNA may include a first input transistor that receives a first signal from the first output terminal of the acoustic wave filter and a second input transistor that receives a second signal from the second output terminal of the acoustic wave filter.

A multiplexer includes a common terminal, a first filter connected to the common terminal, a wiring line connecting the common terminal and the reception filter to each other, a second filter connected to a connection node on the wiring line, a third filter connected to a connection node on the wiring line, a wiring line connecting the connection node and the transmission filter to each other, a wiring line connecting the connection node and the first filter to each other, and an inductor connected between a wiring region of the wiring line that extends from the connection node to the first filter and the ground or between the wiring line and the ground. The length of a portion of the wiring line extending from the common terminal to the connection node is longer than the length of a portion of the wiring line extending from the common terminal to the connection node.