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.

According to one embodiment, in a biquad filter, an output terminal of a first integrator is connected to an input terminal in a negative pole side of a second integrator, an output terminal of the first integrator is connected to a first input terminal in a negative pole side of an adder through the inversion amplifier, an output terminal of the second integrator is connected to a second input terminal in the negative pole side of the adder, an input terminal to which an input signal is input is connected to a third input terminal in the negative side of the adder, and an output terminal of the adder is connected to an input terminal in a negative pole side of the first integrator.

An active feedback RF resonator has a signal loop having a signal input and a signal output. The signal loop has a variable gain stage and at least one variable resonator, each variable resonator comprising an inductance element and a variable capacitance element comprising a number of switched fixed value capacitors and a variable capacitor. A phase noise of the active feedback RF signal has a maximum value for an operating frequency of the variable resonator that is based on an operating range of the variable 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.

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 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.

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.

Self-interference cancellers are provided. The self-interference cancellers can include multiple second-order, N-path G.sub.m-C filters. Each filter can be configured to cancel self-interference on a channel of a desired bandwidth. Each filter can be independently controlled using a variable transmitter resistance, a variable receiver resistance, a variable baseband capacitance, a variable transconductance, and a variable time shift between local oscillators that control switches in the filter. By controlling these variables, magnitude, phase, slope of magnitude, and slope of phase of the cancellers frequency responses can be controlled for self-interference cancellation. A calibration process is also provided for configuring the canceller.

A method of stabilizing a variable filter for an analog electromagnetic signal against circuit oscillation includes the steps of: providing a signal loop comprising a signal input, a signal output, and a plurality of variable circuit elements connected in the signal loop, the plurality of variable circuit elements comprising an adjustable resonator and an adjustable gain block, the signal loop having a variable frequency response that is characterized by a central frequency, a frequency passband, a response Q, and an operating point and a resonator response curve that are plottable in a Cartesian s-plane having an origin, a real axis, and an imaginary axis; and maintaining stability of the variable filter within an operating range by controlling the adjustable resonator and the adjustable gain block such that, in the Cartesian s-plane, the resonator response curve satisfies an orthogonality stability condition.

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.