A filter device includes a first filter and a second filter. The first filter and the second filter are disposed in parallel between a first terminal and a second terminal. A first passband of the filter device includes at least part of a second passband of the first filter. The first passband includes at least part of a third passband of the second filter. The second passband is narrower than the first passband. The third passband is narrower than the first passband. The third passband has a center frequency higher than a center frequency of the second passband. The first filter includes multiple elastic wave resonators and a first capacitive element. The first capacitive element is connected in parallel with the first elastic wave resonator.

An acoustic wave filter includes a divided resonator group and series arm resonators in a path connecting an input-output terminal and an input-output terminal to each other and parallel arm resonators each between a node in the path described above and the ground. The divided resonator group, the series arm resonators, and the parallel arm resonators each include an acoustic wave resonator including an interdigital transducer electrode on a piezoelectric substrate. The divided resonator group includes divided resonators coupled in series with each other. The IDT electrode included in the divided resonator includes a first withdrawal electrode. The IDT electrode included in the divided resonator includes a second withdrawal electrode different from the first withdrawal electrode with respect to the electrode finger structure.

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.

Examples described herein provide selective filtering by a network device for continuous 5 GHz and 6 GHz operation. Examples may include receiving, by the network device, a first signal in a 5 GHz band, and generating, by the network device, a second signal in a 6 GHz band. Examples may include selecting, by the network device, a first filter or a second filter to be applied the first signal in the 5 GHz band, wherein the first filter allows a lower frequency band to pass than the second filter in the 5 GHz band, selecting, by the network device, a third filter or a fourth filter to be applied to the second signal in the 6 GHz band, wherein the third filter allows a lower frequency band to pass than the fourth filter in the 6 GHz band, and simultaneously applying, by the network device, the selected first or second filter to the first signal and the selected third or fourth filter to the second signal.

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.

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.

Aspects of this disclosure relate to an acoustic wave filter with parallel band pass filters. Each band pass filter can be an acoustic wave filter having a passband. One of the parallel band pass filters can have higher passband frequencies than another of the parallel band pass filters. The passbands of the parallel band pass filters can overlap in an overlap band. One of the parallel band pass filters can have a higher impedance in the overlap band than another of the parallel band pass filters.

An RF triplexer circuit device using modified lattice, lattice, and ladder circuit topologies. The devices can include four resonator devices and four shunt resonator devices. In the ladder topology, the resonator devices are connected in series from an input port to an output port while shunt resonator devices are coupled the nodes between the resonator devices. In the lattice topology, a top and a bottom serial configurations each includes a pair of resonator devices that are coupled to differential input and output ports. A pair of shunt resonators is cross-coupled between each pair of a top serial configuration resonator and a bottom serial configuration resonator. The modified lattice topology adds baluns or inductor devices between top and bottom nodes of the top and bottom serial configurations of the lattice configuration. These topologies may be applied using single crystal or polycrystalline bulk acoustic wave (BAW) resonators.

Embodiments of this disclosure relate to bulk acoustic wave resonators on a substrate. The bulk acoustic wave resonators include a first bulk acoustic wave resonator, a second bulk acoustic wave resonator, a conductor electrically connecting the first bulk acoustic wave resonator to the second bulk acoustic wave resonator, and an air gap positioned between the conductor and a surface of the substrate.

Examples described herein provide selective filtering by a network device for continuous 5 GHz and 6 GHz operation. Examples may include receiving, by the network device, a first signal in a 5 GHz band, and generating, by the network device, a second signal in a 6 GHz band. Examples may include selecting, by the network device, a first filter or a second filter to be applied the first signal in the 5 GHz band, wherein the first filter allows a lower frequency band to pass than the second filter in the 5 GHz band, selecting, by the network device, a third filter or a fourth filter to be applied to the second signal in the 6 GHz band, wherein the third filter allows a lower frequency band to pass than the fourth filter in the 6 GHz band, and simultaneously applying, by the network device, the selected first or second filter to the first signal and the selected third or fourth filter to the second signal.