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.

A high-order filter with a capacitive inner tapping technique is disclosed. The filter includes an inductor and a first resonant circuit including a first portion of the inductor and a first capacitor. The first resonant circuit is configured to attenuate first frequency components of an input signal above a cutoff frequency to generate a filtered signal. The filter further includes a second resonant circuit coupled in parallel with the first resonant circuit and including the first portion of the inductor and a second capacitor. The second resonant circuit is configured to attenuate the first frequency components of the input signal to generate the filtered signal. A third resonant circuit includes a second portion of the inductor and a third capacitor, wherein the third resonant circuit is configured to attenuate second frequency components of the filtered signal above the cutoff frequency to generate an output signal.

Embodiments of the present disclosure provide an integrated circuit (IC) structure including: a first conductive layer of a device structure; a second conductive layer of the device structure vertically separated from the first conductive layer, wherein a load resistor couples the second conductive layer to ground; a t-coil having a first end coupled to the first conductive layer, and a second end coupled to the second conductive layer; and a variable capacitor having a first end coupled to the first conductive layer, and a second end coupled to the second conductive layer, the variable capacitor having an adjustable capacitance.

An impedance matching circuit (31) includes inductors (311L and 312L) that are connected in series, a switch (311S) that includes a first terminal connected to an end of the inductor (311L) and a second terminal and that switches between connection and disconnection between the first terminal and the second terminal, a switch (312S) that includes a third terminal connected to a connection point of the other end of the inductor (311L) and an end of the inductor (312L) and a fourth terminal and that switches between connection and disconnection between the third terminal and the fourth terminal, a switch (313S) that includes a fifth terminal connected to the other end of the inductor (312L) and a sixth terminal and that switches between connection and disconnection between the fifth terminal and the sixth terminal. The second terminal, the fourth terminal, and the sixth terminal are connected to each other.