An audio filter and corresponding method with through-zero linearly variable resonant frequency are described. An example method includes receiving an input signal; receiving one or more control input signals; and providing a resonant filter for electronic music for processing the input signal. The resonant filter can include an exponential times linear multiplication to produce the resonant frequency control responsive to control voltages exponentially for musical octave/semitone control, and linearly for timbre modulation, the waveform being invariant over corresponding exponential changes in pitch of both input signal and filter resonance. The linear modulation can include inverting the sign of a bandpass feedback based on the sign of the resonant frequency variable so as to maintain stability. In the example method, to prevent a glitch on the output when frequency changes sign, a separate highpass output signal may be generated.

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.

Customizable tunable filters are provided herein. In certain implementations, a tunable filter including: a first filter bank including a plurality of high-pass filters each having a different cutoff frequency, and a second filter bank including a plurality of low-pass filters each having a different cutoff frequency. The tunable filter further includes a first pair of switches configured to select a first filter chosen from the first filter bank, and a second pair of switches configured to select a second filter chosen from the second filter bank. The tunable filter operates with a first cutoff frequency of the first filter and with a second cutoff frequency of the second filter.

A reconfigurable microacoustic filter is specified which comprises a ladder-type-like filter topology and a suitably placed adjustable capacitive element.

Embodiments of an apparatus that includes a substrate and an inductor residing in the substrate are disclosed. In one embodiment, the inductor is formed as a conductive path that extends from a first terminal to a second terminal. The conductive path has a shape corresponding to a two-dimensional (2D) lobe laid over a three-dimensional (3D) volume. Since the shape of the conductive path corresponds to the 2D lobe laid over a 3D volume, the magnetic field generated by the inductor has magnetic field lines that are predominately destructive outside the inductor and magnetic field lines that are predominately constructive inside the inductor. In this manner, the inductor can maintain a high quality (Q) factor while being placed close to other components.

A wireless transceiver including a receiver circuit coupled to an RF transceiver node, a tunable notch filter coupled between the RF transceiver node and a reference node, and a controller that programs the tunable notch filter with a selected blocker frequency and that selectively enables the tunable notch filter to attenuate at least one blocker signal. The tunable notch filter may include a variable capacitor and an inductor coupled in series between the RF transceiver node and ground. The inductor of the tunable notch filter may include a bondwire coupled between a semiconductor die and a semiconductor package. The inductance may include a physical inductor mounted on the package or a printed circuit board. The tunable notch filter may be enabled by a switch selectively coupling the filter to either the RF transceiver node or ground. The variable capacitor may be digitally programmed with digital values stored in a memory.

A multi-tune filter system and a control system for operating the multi-tune filter system are described herein. The multi-tune filter system is a tunable frequency range filter. Further, the multi-tune filter system is a digitally programmable filter with an adjustable passband between first and second customizable frequency bounds f1, f2.

A wireless transceiver including a receiver circuit coupled to an RF transceiver node, a tunable notch filter coupled between the RF transceiver node and a reference node, and a controller that programs the tunable notch filter with a selected blocker frequency and that selectively enables the tunable notch filter to attenuate at least one blocker signal. The tunable notch filter may include a variable capacitor and an inductor coupled in series between the RF transceiver node and ground. The inductor of the tunable notch filter may include a bondwire coupled between a semiconductor die and a semiconductor package. The inductance may include a physical inductor mounted on the package or a printed circuit board. The tunable notch filter may be enabled by a switch selectively coupling the filter to either the RF transceiver node or ground. The variable capacitor may be digitally programmed with digital values stored in a memory.

A tank circuit (200) includes a tunable resonator subcircuit (210) having a first control input and having an effective parallel resistance that varies with tuning of the tunable resonator subcircuit (210). The tank circuit (200) further comprises a variable negative-resistance subcircuit (250) having a second control input and coupled in parallel to the tunable resonator subcircuit (210), where the variable negative-resistance subcircuit (250) is configured to provide a variable negative resistance, responsive to the control input, so as to increase the effective parallel resistance of the tank circuit (200).

A method and apparatus for modifying or controlling a resonator connected to a signal loop having an input (18828), an output (18822), and a closed loop frequency response. The signal loop has a primary resonator (18810) having a primary frequency response. There is at least one adjustable resonator (18812) having an adjustable frequency (f) and a secondary Q-factor. An adjustable scaling block (18824) applies a gain factor (g). A controller is connected to the at least one adjustable resonator (18812) and the adjustable scaling block (18824). The controller has instructions to adjust the closed loop frequency response toward a desired closed loop frequency response by controlling the adjustable frequency (f) of the at least one adjustable resonator (18812) and the gain factor (g) of the adjustable scaling block (18824).