A wireless communication device includes a first transceiver operable according to a first radio technology and a second transceiver operable according to a second radio technology and operable concurrently with the first transceiver. The wireless communication device further includes an antenna configured to transmit radio transmissions of the second transceiver, and a filter circuit coupling the second transceiver with the antenna. The filter circuit includes a first frequency path and a second frequency path in parallel. The first frequency path passes a first set of frequencies of the radio transmissions and the second frequency path passes a second set of frequencies of the radio transmissions. One of the first frequency path or the second frequency path is configured to filter the radio transmissions of the second transceiver to remove signals corresponding to the one or more operating frequencies of the first transceiver from the radio transmissions of the second transceiver.

A multiplexer includes a band pass filter configured to pass a signal in a predetermined frequency band between a first terminal and a common terminal connected to an antenna, and a band elimination filter configured to attenuate a signal in the predetermined frequency band between a second terminal and the common terminal and includes resonators connected in series with a line between the second terminal and the common terminal. The resonators include a first resonator having a lowest resonant frequency and a second resonator disposed on a side of the common terminal from the first resonator.

A filter includes a plurality of series portions each including one or more series resonators, and a plurality of shunt portions each including one or more shunt resonators. At least one of the plurality of shunt portions includes two shunt resonators connected to each other in anti-series, and antiresonance frequencies of the two shunt resonators are arranged externally of a passband.

A front end module includes a base filter configured to operate as a bandpass filter passing a pass band of an input radio frequency signal; a switch connected to the base filter, and a first notch filter and a second notch filter selectively connected to the base filter through the switch, wherein a stop band of the first notch filter and a stop band of the second notch filter overlap the pass band of the base filter in a band equal to or higher than a center frequency of the pass band of the base filter.

An RF integrated circuit device can includes a substrate and a High Electron Mobility Transistor (HEMT) device on the substrate including a ScAlN layer configured to provide a buffer layer of the HEMT device to confine formation of a 2DEG channel region of the HEMT device. An RF piezoelectric resonator device can be on the substrate including the ScAlN layer sandwiched between a top electrode and a bottom electrode of the RF piezoelectric resonator device to provide a piezoelectric resonator for the RF piezoelectric resonator device.

Harmonic suppression in bulk acoustic wave duplexer. In some embodiments, a filter circuit can include an input node and an output node, and a first assembly having one or more bulk acoustic wave (BAW) resonators implemented electrically between the input node and the output node, and configured to filter a signal. The filter circuit can further include a second assembly having one or more surface acoustic wave (SAW) resonators implemented electrically relative to the first assembly, and configured to suppress one or more harmonics resulting from the filtering of the signal by the first assembly.

In accordance with an embodiment, a method of operating an RF system includes filtering a first wideband RF signal using a wideband filter bank. Filtering the first RF signal includes separating the first wideband RF signal into frequency cluster signals, where each frequency cluster signal of the frequency cluster signals includes different frequency ranges, the first wideband RF signal includes multiple RF bands, and each of the different frequency ranges comprises a plurality of RF bands of the multiple RF bands. The method further includes band stop filtering at least one of the frequency cluster signals to produce a band stopped frequency cluster signal.

Acoustic wave filter devices is disclosed. The device includes a piezoelectric layer, an input electrode and an output electrode located on a top surface of the piezoelectric layer and physically separated from one another, and a counter electrode having a top surface connected to a bottom surface of the piezoelectric layer. The input and output electrodes each include a base and at least one extension extending from the base. The at least one extension of the input electrode extending alongside and in a generally opposite direction to and separated by a gap width from an adjacent extension of the at least one extensions of the output electrode. In some embodiments, the at least one extension of the input or output electrodes has a width that can changes from a first end of the at least one extension to a second end.

A wireless communication device includes a first transceiver operable according to a first radio technology and a second transceiver operable according to a second radio technology and operable concurrently with the first transceiver. The wireless communication device further includes an antenna configured to transmit radio transmissions of the second transceiver, and a filter circuit coupling the second transceiver with the antenna. The filter circuit includes a first frequency path and a second frequency path in parallel. The first frequency path passes a first set of frequencies of the radio transmissions and the second frequency path passes a second set of frequencies of the radio transmissions. One of the first frequency path or the second frequency path is configured to filter the radio transmissions of the second transceiver to remove signals corresponding to the one or more operating frequencies of the first transceiver from the radio transmissions of the second transceiver.

A notch filter includes a first inductor coupled between an input node and an output node, a dual-resonator structure coupled between the input node and the output node, and a second inductor coupled between the dual-resonator structure and ground, and a bandpass filter includes a capacitor coupled between an input node and an output node, and a dual-resonator structure coupled between the input node, the output node, and ground.