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.

In accordance with an embodiment, a method of operating an RF system includes generating a first RF signal having a first frequency; filtering the generated first RF signal to form a first filtered transmitted signal; producing a first coupled signal and a first transmitted signal from the first filtered transmitted signal; transmitting the first transmitted signal; transmitting a second RF signal having a second frequency; bandpass filtering the first coupled signal to form a first tunable bandpass filtered signal; and measuring a parameter of the first tunable bandpass filtered signal.

In accordance with an embodiment, a method of operating an RF system includes generating a first RF signal having a first frequency; filtering the generated first RF signal to form a first filtered transmitted signal; producing a first coupled signal and a first transmitted signal from the first filtered transmitted signal; transmitting the first transmitted signal; transmitting a second RF signal having a second frequency; bandpass filtering the first coupled signal to form a first tunable bandpass filtered signal; and measuring a parameter of the first tunable bandpass filtered signal.

A filter device includes series and parallel arm resonators provided at a filter chip and inductors electrically connected in series with respective ones of the parallel arm resonators. A first inductor having the highest inductance of the inductors is electrically connected in series with a first parallel arm resonator having the highest anti-resonant frequency of the parallel arm resonators. One end of the first parallel arm resonator and one end of a second parallel arm resonator in other ones of the parallel arm resonators are electrically connected to a same wiring line in wiring lines separated by the series arm resonators on a line electrically connecting an input terminal and an output terminal of the filter chip. The other ends of the first and second parallel arm resonators are respectively electrically connected to first and second ground terminals of the filter chip.

A filter device includes series and parallel arm resonators provided at a filter chip and inductors electrically connected in series with respective ones of the parallel arm resonators. A first inductor having the highest inductance of the inductors is electrically connected in series with a first parallel arm resonator having the highest anti-resonant frequency of the parallel arm resonators. One end of the first parallel arm resonator and one end of a second parallel arm resonator in other ones of the parallel arm resonators are electrically connected to a same wiring line in wiring lines separated by the series arm resonators on a line electrically connecting an input terminal and an output terminal of the filter chip. The other ends of the first and second parallel arm resonators are respectively electrically connected to first and second ground terminals of the filter chip.

A resonator element for use in a filter is provided. The resonator element includes a first resonator acoustically coupled to a second or third resonator or both. The first resonator has terminals for incorporation in a filter structure. A tuning circuit is coupled to the second or third resonator or both to enable tuning of the resonator element. The tuning circuit includes a variable capacitor and an inductor.

A resonator element for use in a filter is provided. The resonator element includes a first resonator acoustically coupled to a second or third resonator or both. The first resonator has terminals for incorporation in a filter structure. A tuning circuit is coupled to the second or third resonator or both to enable tuning of the resonator element. The tuning circuit includes a variable capacitor and an inductor.

An acoustic resonator filter package includes an acoustic resonator including a piezoelectric layer, a first electrode disposed on a first surface of the piezoelectric layer, and a second electrode disposed on a second surface of the piezoelectric layer; a first substrate having an upper surface on which the acoustic resonator is disposed, the first substrate comprising a first coupling member surrounding the acoustic resonator; a filter spaced apart from the acoustic resonator in an upward direction; a second substrate having a lower surface on which the filter is disposed, the second substrate including a second coupling member disposed above the first coupling member; and a connection member connecting the first coupling member and the second coupling member to each other, the connection member being made of a material different from a material of which the first coupling member and the second coupling member are made.

An acoustic resonator filter package includes an acoustic resonator including a piezoelectric layer, a first electrode disposed on a first surface of the piezoelectric layer, and a second electrode disposed on a second surface of the piezoelectric layer; a first substrate having an upper surface on which the acoustic resonator is disposed, the first substrate comprising a first coupling member surrounding the acoustic resonator; a filter spaced apart from the acoustic resonator in an upward direction; a second substrate having a lower surface on which the filter is disposed, the second substrate including a second coupling member disposed above the first coupling member; and a connection member connecting the first coupling member and the second coupling member to each other, the connection member being made of a material different from a material of which the first coupling member and the second coupling member are made.

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.