The present embodiment relates to a double-faced display device generating sound by directly vibrating a display panel and includes: a first display panel and a second display panel disposed at the front and rear surface thereof, respectively; a single sound generating actuator connected to the first display panel and the second display panel to simultaneously vibrate the first display panel and the second display panel and thus generate sound; and a support part configured to support the sound generating actuator, the first display panel, and the second display panel. The present embodiment does not require a separate speaker and thus can achieve a thin or slim display device, and can improve the localization or the quality of sound output in opposite directions in the double-faced display device.

A multi-stage matching network filter circuit device. The device comprises bulk acoustic wave (BAW) resonator device having an input node, an output node, and a ground node. A first matching network circuit is coupled to the input node. A second matching network circuit is coupled to the output node. A ground connection network circuit coupled to the ground node. The first or second matching network circuit can include an inductive ladder network including a plurality of series inductors in a series configuration and a plurality of grounded inductors wherein each of the plurality of grounded inductors is coupled to the connection between each connected pair of series inductors. The inductive ladder network can include one or more LC tanks, wherein each of the one or more LC tanks is coupled between a connection between a series inductor and a subsequent series inductor, which is also coupled to a grounded inductor.

In accordance with an embodiment, an RF system includes a transmit path having a first tunable transmit band stop filter, and a power amplifier coupled to an output of the first tunable transmit band stop filter, where the first tunable transmit band stop filter is configured reject a receive frequency and pass a transmit frequency; a receive path comprising an LNA; and a duplex filter having a transmit path port coupled to an output of the power amplifier, a receive path port coupled to an input of the LNA, and an antenna port, where the duplex filter is configured to pass the transmit frequency and reject the receive frequency between the antenna port and the transmit path port, pass the receive frequency and reject the transmit frequency between the antenna port and the receive path port.

A high-frequency module includes a propagation path that has a simple structure and improves filter characteristics by causing an inductor and a matching network to electromagnetic field couple with each other such that attenuation characteristics outside of a frequency band of a transmission signal are improved without increasing the size of the high-frequency module. In addition, unintended electromagnetic field coupling between a first filter and the inductor is significantly reduced or prevented by a shield electrode. Therefore, unintended propagation of a high-frequency signal is significantly reduced or prevented. Therefore, the attenuation characteristics outside of the frequency band of transmission signal input to the transmission terminal are improved more effectively.

An acoustic wave device is provided with a low-frequency side filter having a low-frequency side passband, a high-frequency side filter having a high-frequency side passband, and first and second balanced terminals. The low-frequency side filter is connected to a first unbalanced terminal. The low-frequency side passband is a frequency band from a first minimum frequency to a first maximum frequency. The high-frequency side filter is connected to a second unbalanced terminal. The high-frequency side passband is a frequency band from a second minimum frequency to a second maximum frequency. The low-frequency side filter includes a first longitudinally-coupled acoustic wave resonator and a first one-terminal pair acoustic wave resonator connected in series to the first longitudinally-coupled acoustic wave resonator. An antiresonant frequency of the first one-terminal pair acoustic wave resonator is set to be higher than the first maximum frequency and lower than the second minimum frequency.

A surface acoustic wave filter device includes surface acoustic wave filters, one of which includes a longitudinally coupled resonator-type first filter section and a longitudinally coupled resonator-type second filter section. The second filter section is electrically connected in parallel or series with the first filter section on at least one of an input signal side and an output signal side. The first filter section includes a first IDT group including three IDTs. The second filter section includes a second IDT group including three IDTs. Another surface acoustic wave filter includes a third IDT group that is cascade connected to the first filter section and the second filter section and includes IDTs arranged in order in a line in a surface acoustic wave propagation direction.

Techniques and configurations are disclosed for bulk acoustic wave resonator (BAWR) tuner circuits and their use in integrated circuit (IC) packages and mobile communication devices for radio frequency (RF) communication. In some embodiments, a mobile communication device may include an antenna; a transmitter circuit having an output port, a tuner circuit having one or more BAWRs, an antenna port coupled to the antenna, a transmitter port coupled to the output port of the transmitter circuit, and a control port; and a control circuit, coupled to the control port, configured to adjust an impedance of the tuner circuit, via adjustment of a BAWR or another component of the tuner circuit, based at least in part on an impedance of the antenna. Other embodiments may be described and/or claimed.

A compensation circuit reduces the negative effects of antenna-to-antenna coupling between proximately located antennas. The compensation circuit is coupled between first and second antenna ports. A first transmit/receive path extends from radio frequency (RF) circuitry to the first antenna port. A second transmit/receive path extends from the RF circuitry to the second antenna port. Antennas are coupled to each of the antenna ports. The compensation circuit includes negatively coupled first and second inductors, which are coupled in series between the first antenna port and the second antenna port. At least one shunt acoustic resonator is coupled between a fixed voltage node and a common node between the first and second inductors. In operation, the compensation circuit presents a negative capacitance between the first antenna port and the second antenna port over the first frequency range to reduce the effects of the antenna-antenna coupling.

A filter using bulk acoustic wave resonators (BAWRs) is provided including BAWRs connected in series or in parallel to each other. A BAWR set is configured by connecting an inductance and capacitance (L/C) element to each BAWR in series or in parallel.

The specification relates to an RF filter in which characteristic filter variables have a decreased dependency on tuning. A filter in this case comprises series-interconnected basic elements that each have an electroacoustic resonator and impedance converters interconnected in series between the basic elements.