Apparatus and methods for control and calibration of tunable filters are provided. In certain embodiments, a tunable filter includes at least one controllable component (for instance, a controllable inductor or a controllable capacitor) having a value that changes or adjusts a center frequency of the tunable filter. For example, the controllable component can correspond to a controllable inductor or a controllable capacitor of an inductor-capacitor (LC) resonator of the tunable filter. The tunable filter further includes a control circuit implemented with an approximation function for estimating a value of the controllable component for achieving a desired center frequency indicated by a frequency control signal.

In one embodiment, a tuning network includes: a controllable capacitance; a first switch coupled between the controllable capacitance and a reference voltage node; a second switch coupled between the controllable capacitance and a third switch; the third switch coupled between the second switch and a second voltage node; a fourth switch coupled between the second voltage node and a first inductor; the first inductor having a first terminal coupled to the fourth switch and a second terminal coupled to at least the second switch; and a second inductor having a first terminal coupled to the second terminal of the first inductor and a second terminal coupled to the controllable capacitance.

Disclosed are a power matching method and apparatus for wireless charging, and a wireless charging apparatus. The method includes receiving first sensing information sensed from a transmitting coil of the wireless transmitter, wherein the transmitting coil includes at least one of a capacitor assembly with adjustable capacitance and an inductor assembly with adjustable inductance; detecting whether resonant frequency has changed according to the first sensing information; and adjusting at least one of capacitance of the capacitor assembly in the transmitting coil of the wireless transmitter and inductance of the inductor assembly in the transmitting coil in response to the resonant frequency changing to make transmitting power of the wireless transmitter be matched with receiving power of a wireless receiver in the wireless charging system, wherein the first sensing information comprises at least one of a first sensing voltage value and a first sensing current value.

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.

An adjustable inductor including a core defining a plurality of gaps, a material positioned in the gaps, at least one winding wound on the core, a force-applying structure, and a film substantially covering the adjustable inductor. The force-applying structure is operable to apply a force to the core to adjust the gaps and thereby an inductance of the adjustable inductor. The film is configured to prevent movement of force-applying structure when below a predetermined temperature threshold, and allow movement of the force-applying structure when above the predetermined threshold.

A tuned single-coil inductor is implemented between a signal driver output and external contact of an ESD-protected integrated circuit (IC) die and more specifically between the parasitic capacitances of the signal driver and the contact-coupled ESD (electrostatic discharge) element to form a Pi (π) filter that enhances signaling bandwidth at the target signaling rate of the IC die. The signal driver may be implemented with output-stage data serialization circuitry disposed in series between source terminals of a thick-oxide drive transistor and a power rail to avoid explicit level-shifting circuitry between the relatively low core voltage domain and relatively high I/O voltage domain.

A radio frequency circuit includes a multilayer substrate, series arm circuits in a first path connecting the input/output terminals (T1 and T2) on the multilayer substrate, a parallel arm circuit in a second path connecting a node on the first path and a ground, a wiring A on the multilayer substrate connected to the input/output terminal (T1) as a part of the first path, a wiring B on the multilayer substrate connected to the input/output terminal (T2) as a part of the first path, and a wiring C on the multilayer substrate as a part of the second path. The parallel arm circuit includes an impedance variable circuit, the wiring A and the wiring B in a layer different from the multilayer substrate. When viewed in a plan view, the wiring C does not overlap with the wiring A and the wiring B.

Embodiments of an SLR antenna having differential signal contacts and a tuning circuit configured to tune the at least one resonance frequency of the SLR antenna to a predetermined operational frequency are disclosed. Embodiments of a tuning circuit include a balun transformer connected between the differential signal contacts of the SLR antenna and a single-ended input/output contact, a first variable capacitance connected between the balun transformer and the single-ended input/output contact, and a variable reactive component connected between the differential signal contacts of the SLR antenna and between differential contacts of the balun transformer.

A filtering circuit includes a filter, a frequency divider, and a control circuit. The filter is configured to generate a first oscillating signal according to a control signal in a first mode, and perform a filtering process according to the control signal in a second mode. A frequency of the first oscillating signal is determined according to the control signal. The frequency divider is coupled to the filter and configured to divide the frequency of the first oscillating signal to generate a frequency-divided signal. The control circuit is coupled to the filter and the frequency divider, and configured to compare a frequency of the frequency-divided signal and a frequency of a second oscillating signal so as to adjust the control signal in the first mode. A center frequency of a passband of the filter in the second mode is determined according to the adjusted control signal.

In a first approach, a reconfigurable radio frequency (RF) filtering module includes a phase-change material (PCM) RF switch bank and an RF filter bank. Each RF filter in the RF filter bank is capable to be engaged and disengaged by a PCM RF switch in the PCM RF switch bank. In a second approach, a tunable RF filter includes PCM RF switches and a capacitor and/or an inductor. Each of the capacitor and/or inductor is capable to be engaged and disengaged by at least one PCM RF switch of the PCM RF switches. In a third approach, an adjustable passive component includes multiple segments and a PCM RF switch. A selectable segment in the multiple segments is capable to be engaged and disengaged by the PCM RF switch. In all approaches, each PCM RF switch includes a PCM and a heating element transverse to the PCM.