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.

In accordance with an embodiment, a method of operating an RF system includes filtering a wideband RF signal using an adjustable center frequency bandpass filter to produce a filtered RF signal; amplifying the filtered RF signal to produce an amplified RF signal; and band stop filtering the amplified RF signal to produce a band stopped RF signal.

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.

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.

In accordance with an embodiment, an RF system includes a transmit path having a transmit RF filter and an adjustable transmit phase shifter/matching network coupled between the transmit RF filter and a transmit antenna port, where the adjustable transmit phase shifter/matching network is configured to transform an impedance of the transmit RF filter at a receive frequency from a first lower impedance to a first higher impedance at the transmit antenna port; and a receive path having a receive RF filter and an adjustable receive phase shifter/matching network coupled between the receive RF filter and a receive antenna port, where the adjustable receive phase shifter/matching network is configured to transform an impedance of the receive RF filter at a transmit frequency from a second lower impedance to a second higher impedance at the receive antenna port.

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.

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.

According to some embodiments, an on-chip diplexer circuit is disclosed. The on-chip diplexer circuit includes a LC resonator module, the LC resonator module further comprises a first port, a first LC resonator unit and a second LC resonator unit; a first filter unit, the first filter unit is electrically connected to the first LC resonator unit in the LC resonator module, and the first filter unit is electrically connected to a second port; and a second filter unit, the second filter unit is electrically connected to the second LC resonator unit in the LC resonator module, and the second filter unit is electrically connected to a third port. According to some embodiments, the first LC resonator unit serves as an impedance matching circuit for a first signal having a first resonant frequency and serves as an open circuit for a second signal having a second resonant frequency that is different from the first resonant frequency; the second LC resonator unit serves as an impedance matching circuit for the second signal having the second resonant frequency and serves as an open circuit for the first signal having the first resonant frequency. The first filter unit passes signals with the first resonant frequency; and the second filter unit passes signals with the second resonant frequency.

A semiconductor device capable of reducing in size thereof and suppressing degradation in the characteristics of circuit components is provided. The semiconductor device includes an LC circuit comprised of a spiral inductor provided over a semiconductor substrate and a capacitive element coupled with the spiral inductor. The spiral inductor includes a central area encircled with a metal wiring and a peripheral area other than the central area. The capacitive element is formed in an upper-layer or a lower-layer position corresponding to the peripheral area other than the central area.

An inductor-capacitor (LC) filter includes an inductor having an asymmetric shape including at least one turn. The LC filter also includes serial capacitors coupled to the inductor at only one end of a continuous portion of the inductor. The serial capacitors continues the shape of the inductor. The capacitors are outside of a footprint of the continuous portion of the inductor.