In order to pass a signal having a wide pass bandwidth with respect to a center frequency of a pass band, a surface acoustic wave device includes a first surface acoustic wave element provided with a first pass band; and a second surface acoustic wave element having a second pass band in a high frequency band compared with the first pass band of the first surface acoustic wave element, in which the first surface acoustic wave element and the second surface acoustic wave element have a common input terminal and a common output terminal, and a frequency of a high frequency side of the first pass band of the first surface acoustic wave element is partially overlapped with a frequency of a low frequency side of the second pass band of the second surface acoustic wave element.

A filter device having a pass band and a stop band on a lower frequency side than the pass band includes a filter having a pass band including the pass band, a series arm resonator connected in series to the filter, a first inductor directly connected in series to the series arm resonator, and a parallel arm resonator connected between a node on a path connecting the filter and the series arm resonator and the ground. The parallel arm resonator constitutes a resonance circuit having a resonant frequency at which an attenuation pole corresponding to a high frequency end of the first stop band, and the series arm resonator and the inductor constitute a resonance circuit having an anti-resonant frequency on a lower frequency side than the pass band and having a sub-resonant frequency higher than a resonant frequency of the resonance circuit.

A filter device having a pass band and a stop band on a lower frequency side than the pass band includes a filter having a pass band including the pass band, a series arm resonator connected in series to the filter, a first inductor directly connected in series to the series arm resonator, and a parallel arm resonator connected between a node on a path connecting the filter and the series arm resonator and the ground. The parallel arm resonator constitutes a resonance circuit having a resonant frequency at which an attenuation pole corresponding to a high frequency end of the first stop band, and the series arm resonator and the inductor constitute a resonance circuit having an anti-resonant frequency on a lower frequency side than the pass band and having a sub-resonant frequency higher than a resonant frequency of the resonance circuit.

A variable filter circuit includes a serial arm connected between ports (P1-P2), a parallel arm having a resonator connected in series between ports (P1-P3), and another parallel arm having another resonator connected in series between ports (P2-P3). The serial arm includes an inductor connected between the ports (P1-P2), and the parallel arms include variable capacitances connected in series to the resonators.

A variable filter circuit includes a serial arm connected between ports (P1-P2), a parallel arm having a resonator connected in series between ports (P1-P3), and another parallel arm having another resonator connected in series between ports (P2-P3). The serial arm includes an inductor connected between the ports (P1-P2), and the parallel arms include variable capacitances connected in series to the resonators.

The invention combines two filter technologies on a single device using the same substrate there for. On this substrate a filter circuit is arranged that has a ladder-type or a lattice arrangement of series and parallel impedance elements to provide a hybrid filter having for example a band pass function. The impedance elements are chosen from BAW resonators and LC elements.

The invention combines two filter technologies on a single device using the same substrate there for. On this substrate a filter circuit is arranged that has a ladder-type or a lattice arrangement of series and parallel impedance elements to provide a hybrid filter having for example a band pass function. The impedance elements are chosen from BAW resonators and LC elements.

Aspects of this disclosure relate to a tunable filter with harmonic rejection. The tunable filter includes mutually coupled inductors and a tunable capacitance circuit electrically connected to at least one of the mutually coupled inductors. The tunable capacitance circuit includes N switches configured to adjust effective capacitance of the tunable capacitance circuit to tune harmonic rejection of the tunable filter for at least 2×2.sup.N harmonics. The tunable filter can filter a radio frequency signal. Related methods, radio frequency systems, radio frequency modules, and wireless communication devices are also disclosed.

A radio frequency module includes a radio frequency filter (10), and the radio frequency filter (10) includes a terminal (11), a terminal (12), an impedance element (Z) disposed in series on a path (13) connecting the terminal (11) and the terminal (12), and a parallel arm resonator (P) connected between a node (N) on the path (13) and the ground. The impedance element (Z) is a capacitor or an inductor, capacitance (C) between the ground and a wiring line (14) connecting the node (N) and the parallel arm resonator (P) is larger than capacitance between the ground and a wiring line (16) connecting the impedance element (Z) and a terminal out of the terminal (11) and the terminal (12) having a shorter wiring length to the impedance element (Z) (terminal (11), for example).

An LC resonance element (10) includes a dielectric film (12), a common electrode (11) formed of a thin-film conductor on a lower surface (12D) of the dielectric film, a first capacitor (C1) and a second capacitor (C2) that are connected in series via the common electrode (11) and constitute a thin-film capacitor (TC), first and second external connection terminals (14A, 14B) formed on an upper surface (12U) of the dielectric film, a thin-film conductive wire (16) constituting a thin-film inductor (TL), a first upper electrode (13A) of the first capacitor formed on the upper surface (12U), and a second upper electrode (13B) of the second capacitor formed on the upper surface (12U). The thin-film conductive wire (16) is formed in a region (R2) located on the upper surface (12U) of the dielectric film and outside the common electrode (11) in plan view.