A high-Q factor resonator includes a solenoid having an embedded capacitor assembled in a machinable high-frequency dielectric printed circuit board (PCB), or other substrate. The solenoid comprises a plurality of surface conductors positioned on upper and lower surfaces of the PCB. The solenoid further comprises a plurality of conductive vias extending through the PCB between the surface conductors, and at least two aligned vias are separated by a capacitive gap. A liquid crystal dielectric is embedded within the capacitive gap in order to control the capacitance. Accordingly, a tunable capacitive filter is achieved by changing the dielectric permittivity of the liquid crystal. In one example, a nematic liquid crystal is sealed in the capacitive gap and has its permittivity changed with a low frequency bias to tune the capacitor.

Embodiments of resonator circuits and modulating resonators and are described generally herein. One or more acoustic wave resonators may be coupled in series or parallel to generate tunable filters. One or more acoustic wave resonances may be modulated by one or more capacitors or tunable capacitors. One or more acoustic wave modules may also be switchable in a filter. Other embodiments may be described and claimed.

Certain aspects of the present disclosure provide methods and apparatus for calibrating a tunable active filter. One example apparatus is a filter circuit that generally includes a tunable active filter comprising at least one amplifier and a first feedback path coupled between an input and an output of the at least one amplifier, the first feedback path comprising at least one switch; and an amplitude limiter coupled to the tunable active filter and comprising at least one transistor disposed in a second feedback path coupled between the input and the output of the at least one amplifier.

Embodiments of resonator circuits and modulating resonators and are described generally herein. One or more acoustic wave resonators may be coupled in series or parallel to generate tunable filters. One or more acoustic wave resonances may be modulated by one or more capacitors or tunable capacitors. One or more acoustic wave modules may also be switchable in a filter. Other embodiments may be described and claimed.

A method and apparatus for modifying or controlling a resonator connected to a signal loop having an input, an output, and a closed loop frequency response. The signal loop has a primary resonator having a primary frequency response. There is at least one adjustable resonator having an adjustable frequency and a secondary Q-factor. An adjustable scaling block applies a gain factor. A controller is connected to the at least one adjustable resonator and the adjustable scaling block. The controller has instructions to adjust the closed loop frequency response toward a desired closed loop frequency response by controlling the adjustable frequency of the at least one adjustable resonator and the gain factor of the adjustable scaling block.

A variable filter has a signal loop defined between a signal input and a signal output. A plurality of circuit elements connected in the signal loop, the plurality of circuit elements comprising a frequency tunable resonator, and an adjustable scaling block that applies a gain factor that is adjustable in a range that comprises a positive gain and a negative gain. A controller is connected to 1) tune the frequency tunable resonator; and to 2) adjust the gain factor of the adjustable scaling block between a negative gain factor to a positive gain factor providing for variable Q independent of frequency.

Embodiments of resonator circuits and modulating resonators and are described generally herein. One or more acoustic wave resonators may be coupled in series or parallel to generate tunable filters. One or more acoustic wave resonances may be modulated by one or more capacitors or tunable capacitors. One or more acoustic wave modules may also be switchable in a filter. Other embodiments may be described and claimed.

A circuit comprises a Sallen-Key filter, which includes a source follower that implements a unity-gain amplifier; and a programmable-gain amplifier coupled to the Sallen-Key filter. The circuit enables programmable gain via adjustment to a current mirror copying ratio in the programmable-gain amplifier, which decouples the bandwidth of the circuit from its gain settings. The programmable-gain amplifier can comprise a differential voltage-to-current converter, a current mirror pair, and programmable output gain stages. The Sallen-Key filter and at least one branch in the programmable-gain amplifier can comprise transistors arranged in identical circuit configurations.

Tunable filter circuitry includes a series acoustic resonator between first and second nodes and a compensation circuit in parallel with the series acoustic resonator. The compensation circuit includes first and second inductors coupled in series between the first node and the second node, wherein the first inductor and the second inductor are negatively coupled with one another and a common node is provided between the first and second inductors. The compensation circuit also includes first and second shunt acoustic resonators, which are coupled in parallel with one another between the common node and a fixed voltage node. A first variable capacitor is also coupled between the common node and the fixed voltage node, wherein changing a capacitance of the first variable capacitor changes a bandwidth of a passband of the filter circuitry.

Embodiments of resonator circuits and modulating resonators and are described generally herein. One or more acoustic wave resonators may be coupled in series or parallel to generate tunable filters. One or more acoustic wave resonances may be modulated by one or more capacitors or tunable capacitors. One or more acoustic wave modules may also be switchable in a filter. Other embodiments may be described and claimed.