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 resonator includes a piezoelectric body and electrode fingers. The electrode fingers are positioned on the piezoelectric body and arrayed in a propagation direction of acoustic waves. The electrode fingers include a first and second electrode finger groups. Electrode fingers are formed between adjacent two of the electrode fingers of the other electrode group. A duty ratio of the electrode fingers of the first and second electrode finger groups is gradually changed along one of opposite directions specifying the propagation direction by first and second change amounts, respectively which are different, and in the opposite direction. In a region in which the electrode fingers are positioned, a pitch between the electrode fingers is changed to cancel an effect of a difference in the duty ratio of the electrode fingers on a difference in resonance frequency.

Multiplexers are disclosed. A multiplexer can include a first filter and a second filter that are coupled to a common node. The second filter can include a first type of acoustic wave resonators (e.g., bulk acoustic wave resonators) and a series acoustic wave resonator of a second type (e.g., a surface acoustic wave resonator) that is coupled between the acoustic wave resonators of the first type and the common node. The first filter can provide a single-ended radio frequency signal. In certain embodiments, the first filter can be a receive filter and the second filter can be a transmit filter.

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.

Multiplexers are disclosed. A multiplexer can include a first filter and a second filter that are coupled to a common node. The second filter can include a first type of acoustic wave resonators (e.g., bulk acoustic wave resonators) and a series acoustic wave resonator of a second type (e.g., a surface acoustic wave resonator) that is coupled between the acoustic wave resonators of the first type and the common node. The first filter can provide a single-ended radio frequency signal. In certain embodiments, the first filter can be a receive filter and the second filter can be a transmit filter.

An acoustic wave filter includes an input end, an output end, and a series arm connecting the input end and the output end. The series arm includes n (n=3) acoustic wave resonators connected in series in an order of first, second, and third acoustic wave resonators. The first, second, and third acoustic wave resonators include multiple electrode fingers. The first, second, and third acoustic wave resonators include an mth acoustic wave resonator (m is a natural number of 1<m<n, where m=2). An electrode finger pitch of the second acoustic wave resonator is smallest among electrode finger pitches of the first, second, and third acoustic wave resonators.

A liquid fuel system for a turbine engine may include one or more sensors configured to generate sensor outputs corresponding to one or more phase properties of a fuel supplied to the turbine engine through a fuel pathway, and a controller configured to generate control commands configured to control one or more controllable components of the liquid fuel system based at least in part on the sensor outputs. The one or more sensors may include one or more phase detection sensors. The fuel may include hydrogen. The fuel may have a liquid phase state.

The radio frequency module includes a mounting board, a first metal member, and a second metal member. The first metal member and the second metal member are disposed on the mounting board. The first metal member has a longitudinal direction along a first direction in plan view from a thickness direction of the mounting board. The second metal member has a longitudinal direction along a second direction in plan view from the thickness direction of the mounting board. The first or second metal member is placed between a first electronic component and a second electronic component. The first metal member has a first recessed portion. The second metal member has a through hole and a second recessed portion. The through hole passes through the second metal member in the direction intersecting with the second direction. The second recessed portion faces and is in contact with the first recessed portion.

To provide a radio-frequency module and a communication apparatus capable of achieving more excellent impedance characteristics. A radio-frequency module includes a first acoustic-wave filter (a first reception filter), a second acoustic-wave filter (a second reception filter), a switch (an antenna switch), a first inductor, and a second inductor. The first acoustic-wave filter transmits a signal in a first communication band. The second acoustic-wave filter transmits a signal in a second communication band. The first inductor is provided between ground and a node on a signal path (a second reception path) with which the switch is connected to the second acoustic-wave filter. The second inductor is connected in series between the switch and the first inductor on the signal path.

A multiplexer includes elastic wave filters with different pass bands, a common terminal to which an inductance element is serially connected in a connection path between an antenna element and the common terminal; and an inductance element. Among the elastic wave filters, a reception input terminal of a first reception filter is connected to the common terminal via the inductance element and is connected to a parallel resonator. Transmission output terminals of transmission filters and a reception input terminal of a second reception filter are connected to the common terminal, are connected to series resonators, and are not connected to parallel resonators.