An acoustic wave device includes a piezoelectric substrate made of LiNbO.sub.3, and a dielectric film provided on the piezoelectric substrate to cover first and second IDT electrodes on the piezoelectric substrate. The first and second IDT electrodes include main electrode layers. When wave lengths determined by electrode finger pitches of the first and second IDT electrodes are λ.sub.1 and λ.sub.2, respectively, the average value thereof is λ.sub.0, λ.sub.1/λ.sub.0=1+X, and λ.sub.2/λ.sub.0=1−X, a relationship of 0.05≤X≤0.65 is satisfied. The wavelength λ.sub.1 is the longest, and the wavelength λ.sub.2 is the shortest. In Euler angles (φ, θ, ψ) of the piezoelectric substrate, φ is 0°±5°, ψ is 0°±10°, and θ satisfies Expression 1, wherein a relationship of B.sub.1<T×r≤0.10λ.sub.0 and B.sub.2<T×r≤0.10λ.sub.0 are satisfied.

A multiplexer includes an antenna terminal, first to third filters with different passbands, and first and second phase circuits that adjust the phase of a passing signal. The first filter is connected to the antenna terminal. The second filter is connected to the antenna terminal with the first phase circuit provided between the second filter and the antenna terminal. The third filter is connected to a connection node between the first phase circuit and the second filter with the second phase circuit provided between the third filter and the connection node. In the second filter, an unwanted wave is generated in the first passband of the first filter. The first phase circuit adjusts the phase to provide an impedance in an open state in the first passband at the antenna terminal. The second phase circuit adjusts the phase to provide the impedance in a short-circuited state in the first passband at the connection node.

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).

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).

A filter having a pass band includes a series circuit in which a series arm resonator and a first inductor are connected in series with each other and which forms at least part of a signal path R connecting a first input/output terminal and a second input/output terminal and a parallel arm resonator connected between one end of the series circuit and a ground. The series circuit becomes inductive in the pass band. An anti-resonant frequency of the series arm resonator is higher than a frequency at a higher-frequency end of the pass band. A resonant frequency of the parallel arm resonator is higher than the anti-resonant frequency of the series arm resonator.

A mobile terminal and a method for expanding a bandwidth of a B41 frequency band in LTE are disclosed. The mobile includes a multimode multiband power amplifier, a duplexer, a first surface acoustic wave (SAW) filter, a selection module, and a radio frequency transmission module. When the multimode multiband power amplifier identifies that the initial signal is a signal in the B41 frequency band, the multimode multiband power amplifier determines a frequency band range of the signal in the B41 frequency band and outputs a transmitting signal in the B41 frequency band.

A mobile terminal and a method for expanding a bandwidth of a B41 frequency band in LTE are disclosed. The mobile includes a multimode multiband power amplifier, a duplexer, a first surface acoustic wave (SAW) filter, a selection module, and a radio frequency transmission module. When the multimode multiband power amplifier identifies that the initial signal is a signal in the B41 frequency band, the multimode multiband power amplifier determines a frequency band range of the signal in the B41 frequency band and outputs a transmitting signal in the B41 frequency band.

A filter includes: a piezoelectric substrate; a first acoustic wave resonator located on the piezoelectric substrate and including a pair of first reflectors including first grating electrodes and a pair of first comb-shaped electrodes that is located between the first reflectors and includes first electrode fingers; and a second acoustic wave resonator that is connected in series or parallel with the first acoustic wave resonator, is located on the piezoelectric substrate, and includes a pair of second reflectors including second grating electrodes and a pair of second comb-shaped electrodes that is located between the second reflectors and includes second electrode fingers, an average value of duty ratios of the second grating electrodes being different from an average value of duty ratios of the first grating electrodes, an average value of pitches of the second electrode fingers being substantially equal to an average value of pitches of the first electrode fingers.

A filter includes: a piezoelectric substrate; a first acoustic wave resonator located on the piezoelectric substrate and including a pair of first reflectors including first grating electrodes and a pair of first comb-shaped electrodes that is located between the first reflectors and includes first electrode fingers; and a second acoustic wave resonator that is connected in series or parallel with the first acoustic wave resonator, is located on the piezoelectric substrate, and includes a pair of second reflectors including second grating electrodes and a pair of second comb-shaped electrodes that is located between the second reflectors and includes second electrode fingers, an average value of duty ratios of the second grating electrodes being different from an average value of duty ratios of the first grating electrodes, an average value of pitches of the second electrode fingers being substantially equal to an average value of pitches of the first electrode fingers.

An acoustic wave device includes a piezoelectric substrate made of LiNbO.sub.3, and a dielectric film provided on the piezoelectric substrate to cover first and second IDT electrodes on the piezoelectric substrate. The first and second IDT electrodes include main electrode layers. When wave lengths determined by electrode finger pitches of the first and second IDT electrodes are .sub.1 and .sub.2, respectively, the average value thereof is .sub.0, .sub.1/.sub.0=1+X, and .sub.2/.sub.0=1X, a relationship of 0.05X0.65 is satisfied. The wavelength .sub.1 is the longest, and the wavelength .sub.2 is the shortest. In Euler angles (, , ) of the piezoelectric substrate, is 05, is 010, and satisfies Expression 1, wherein a relationship of B.sub.1<Tr0.10.sub.0 and B.sub.2<Tr0.10.sub.0 are satisfied.