A resonator element for use in a filter is provided. The resonator element includes a first resonator acoustically coupled to a second resonator. The first resonator has terminals for incorporation in a filter structure. A tuning circuit is coupled to the second resonator to enable tuning of the resonator element.

A tunable passband filter including a signal input port for receiving an input radio frequency (RF) signal, a signal output port for transmitting a filtered output RF signal, a first high-pass section having a first tunable microelectromechanical system (MEMS) switch array to receive the input RF signal from the signal input port, a second high-pass section having a second tunable MEMS switch array to transmit the output RF signal to the signal output port, and a low pass section operatively coupled between the first high-pass section and the second high-pass section, and having each of a first tunable MEMS bridge array, a second tunable MEMS bridge array, and a high impedance line. The tunable passband filter is configured to filter the input RF signal to yield the filtered output RF signal.

RF circuitry, which includes a first passive voltage-gain network and a first MOS-based RF receive amplifier, is disclosed. The first passive voltage-gain network provides a first passive RF receive signal using a first RF receive signal, such that an energy of the first passive RF receive signal is obtained entirely from the first RF receive signal by the first passive voltage-gain network. A voltage of the first passive RF receive signal is greater than a voltage of the first RF receive signal. The first MOS-based RF receive amplifier receives and amplifies the first passive RF receive signal to provide a first amplified RF receive signal.

In an illustrative example, a device includes an operational amplifier of an active bandpass filter circuit. The device further includes an adjustable resistance device configured to adjust a center frequency associated with the active bandpass filter circuit. The device further includes an adjustable capacitance device configured to adjust the center frequency and a bandwidth associated with the active bandpass filter circuit.

RF communications circuitry, which includes a first tunable RF filter and an RF power amplifier (PA), is disclosed. The first tunable RF filter includes a pair of weakly coupled resonators, and receives and filters a first upstream RF signal to provide a first filtered RF signal. The RF PA is coupled to the first tunable RF filter, and receives and amplifies an RF input signal to provide an RF output signal.

A variable filter circuit includes a serial arm connected between ports (P1-P2), a parallel arm having a resonator connected in series between ports (P1-P3), and another parallel arm having another resonator connected in series between ports (P2-P3). The serial arm includes a capacitor connected between the ports (P1-P2), and the parallel arms include variable capacitances connected in series to the resonators.

Provided is a variable filter circuit that can control the bandwidth and center frequency of a pass band, can realize steep attenuation characteristics in bands close to the pass band, and enables the total number of variable reactance units to be reduced. A variable filter circuit includes an inductor (Ls1) and a capacitor (Cs1), which are connected in series between a first input/output terminal (P1) and a second input/output terminal (P2), and resonators (Re_p1, Re_p2, Re_p3, Re_p4) and variable capacitors (Cc1, Cc2, Cc3, Cc4), which are connected in series between two ends of the inductor (Ls1) and the capacitor (Cs1) and ground connection terminals.

Embodiments of radio frequency (RF) front-end circuitry are disclosed where the RF front-end circuitry includes a tunable RF filter structure and a calibration circuit. The tunable RF filter structure includes (at least) a pair of weakly coupled resonators and defines a transfer function with a passband. The calibration circuit is configured to shape the passband so that the passband defines a center frequency. Additionally, the calibration circuit is configured to detect a phase difference at the target center frequency between the pair of weakly coupled resonators and adjust the phase difference of the pair of weakly coupled resonators at the target center frequency so as to reduce a frequency displacement between the center frequency of the passband and the target center frequency. In this manner, the calibration circuit calibrates the tunable RF filter structure to correct for errors in the center frequency of the passband due to component manufacturing variations.

RF front-end circuitry, which includes a first RF low noise amplifier (LNA) and a first reconfigurable RF filter, is disclosed. The RF front-end circuitry operates in one of a group of operating modes. The first reconfigurable RF filter, which has a first reconfigurable RF filter path, includes a first receive (RX) shunt switching element coupled between the first reconfigurable RF filter path and ground. The first reconfigurable RF filter path is coupled to an input of the first RF LNA. The group of operating modes includes a first operating mode and a second operating mode. During the first operating mode, the first RX shunt switching element is ON. During the second operating mode, the first RX shunt switching element is OFF and the first RF LNA receives and amplifies a first filtered RF receive signal from the first reconfigurable RF filter to provide a first receive signal.

A capacitor circuit includes a first capacitor bank and a second capacitor bank. The first capacitor bank includes p switch-capacitor circuits connected to each other in parallel, where p is a natural number of 2 or more, wherein at least two switch-capacitor circuits among the p switch-capacitor circuits have mutually different capacitance values based on a first weight. The second capacitor bank includes q switch-capacitor circuits connected to each other in parallel, where q is a natural number greater than p, wherein at least two of the q switch-capacitor circuits have mutually different capacitance values based on a second weight different from the first weight.