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 of constructing an RF filter comprises designing an RF filter that includes a plurality of resonant elements disposed, a plurality of non-resonant elements coupling the resonant elements together to form a stop band having a plurality of transmission zeroes corresponding to respective frequencies of the resonant elements, and a sub-band between the transmission zeroes. The non-resonant elements comprise a variable non-resonant element for selectively introducing a reflection zero within the stop band to create a pass band in the sub-band. The method further comprises changing the order in which the resonant elements are disposed along the signal transmission path to create a plurality of filter solutions, computing a performance parameter for each of the filter solutions, comparing the performance parameters to each other, selecting one of the filter solutions based on the comparison of the computed performance parameters, and constructing the RF filter using the selected filter solution.

An acoustic structure is provided. The acoustic structure includes an acoustic resonator structure configured to resonate in a series resonance frequency (e.g., passband frequency) to pass a signal, or cause a series capacitance to block the signal in a parallel resonance frequency (e.g., stopband frequency). The parallel resonance frequency may become higher than the series resonance frequency when the tunable capacitance is lesser than or equal to two times of the series capacitance (C.sub.Tune≤2C.sub.0), or lower than the series resonance frequency when the tunable capacitance is greater than two times of the series capacitance (C.sub.Tune>2C.sub.0). In this regard, the acoustic structure can be configured to include a tunable reactive circuit to generate the tunable capacitance (C.sub.Tune) to adjust the parallel resonance frequency. As such, it may be possible to flexibly configure the acoustic resonator structure to block the signal in desired stopband frequencies.

A power noise filter and a supply modulator including the same, and a wireless communication device including the power noise filter are provided. The power noise filter includes a band stop filter and a low pass filter. The band stop filter includes an inductor and a first capacitor, which are connected in parallel between first and second nodes. The first node receives a first voltage, which is filtered by the band pass filter to thereby generate a second voltage at the second node. The first low pass filter includes the inductor and a second capacitor, which has one end connected to the second node and an opposite end connected to a ground source.

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.

An RF signal is tuned by: producing a first signal at a first frequency using a digital sequence generator; filtering the first signal using a frequency-tunable tracking filter that is tuned to the first frequency, the tracking filter comprising one or more variable resonators; tuning the tracking filter from the first frequency to a second frequency over a transition period; and tuning the first signal to the second frequency by causing the digital sequence generator to transition between two or more states during the transition period. The two or more states are selected such that, immediately after the transition period, the analog signal substantially matches a desired steady state at the second frequency.

A digital conversion system including a sigma-delta converter, a signal generator providing a substantially symmetrical injection signal that is injected into the sigma-delta converter conversion path, bandpass filters for filtering the injection signal and the output of the sigma-delta converter, a correlator that correlates the filtered signals for providing an error signal, and a loop controller that uses the error signal to adjust a resonant frequency of the sigma-delta converter to output a target notch frequency. The loop controller may adjust a resonant frequency of a loop filter of the sigma-delta converter, in which the bandpass filters may each be centered at the target notch frequency at the output of the sigma-delta converter. The correlator may include a complex conjugate block, a multiplier and a mean calculator. The loop controller may include a converter and an amplifier and an integrator or a least-mean square block.

A radio-frequency filter includes a series-arm circuit on a circuit path that connects a first input/output terminal and a second input/output terminal. A parallel-arm circuit is connected to a node on the path and ground. The series-arm circuit includes a first impedance element, a first switch element connected to the first impedance element, and a series-arm resonator connected in parallel to the first impedance element and the first switch element. The parallel-arm circuit includes a first parallel-arm resonator, and a first switch circuit connected in series to the first parallel-arm resonator, the first switch circuit includes a second switch element. The first and second switch elements and the second switch elements include one or more transistors, and a gate width of the transistors included in the second switch element is larger than that of at least one of the transistors included in the first switch element.

The application provides an attenuator and a differential voltage probe, comprising a forward attenuation circuit and a reverse attenuation circuit which are symmetrical with each other, a first compensation unit and a third compensation unit which are symmetrical with each other, a second compensation unit and a fourth compensation unit which are symmetrical with each other, and a differential amplifier; the four compensation units are all adjustable capacitor units composed of constant capacitance; a positive-going signal to be tested is attenuated by the forward attenuation circuit, and frequency characteristics of a preset frequency point are adjusted by the first compensation unit and second compensation unit; a negative-going signal to be tested is attenuated by the reverse attenuation circuit, and frequency characteristics of a preset frequency point are adjusted by the third compensation unit and fourth compensation unit; finally, the difference value is calculated by the differential amplifier, amplified and output.

A filter circuit including a plurality of capacitances and a plurality of inductances including one variable reactance that is either an inductance or a capacitance. The filter circuit has a plurality of resonant modes that each correspond to resonance at a resonant frequency between the variable reactance and one or more of the plurality of inductances and one or more of the plurality of capacitances. The variable reactance is conductively coupled with one or more other inductances and capacitances of the pluralities of inductances and capacitances such that a change in the variable reactance causes a change in a resonant frequency of more than one of the plurality of resonant modes. Front-end modules and wireless communication devices incorporating such a filter circuit and a method using such a filter circuit are also described.