A varainductor includes a signal line, a ground plane, and a floating plane over a substrate. The ground plane is disposed on a side of the signal line, and the first floating plane is disposed between the ground plane and the signal line. An array of switches includes at least two switches configured to selectively electrically connect the ground plane to the floating plane.

In one embodiment, a phase detection circuit includes a current signal input to receive a current signal indicative of a current amplitude of an RF signal and a voltage signal input to receive a voltage signal indicative of a voltage amplitude of the RF signal. A high-pass filter and a low-pass filter are each configured to filter one of (i) the current signal from the current signal input or (ii) the voltage signal from the voltage signal input, wherein the high-pass filter and the low-pass filter collectively cause a substantially 90 degree offset between a phase angle of the current signal and a phase angle of the voltage signal. A phase difference circuit receives the filtered current signal and the filtered voltage signal to determine a phase angle difference between the current signal and the voltage signal.

A resonant magnetic coupling wireless power transfer system with calibration capabilities of the resonant frequencies of its power transmitter(s) and power receiver(s) is disclosed. The system detects the peak voltages of the coil inductors or the resonant capacitors and tunes the resonant capacitors until the detected peak voltages reach their maximal values given proper setup conditions, so as to calibrate the inductor-capacitor (LC) resonance frequencies of the power transmitter(s) and the power receiver(s) in the resonant magnetic coupling wireless power transfer system to achieve the highest power transferred to the load and a high PTE.

A resonant magnetic coupling wireless power transfer system with calibration capabilities of the resonant frequencies of its power transmitter(s) and power receiver(s) is disclosed. The system detects the peak voltages of the coil inductors or the resonant capacitors and tunes the resonant capacitors until the detected peak voltages reach their maximal values given proper setup conditions, so as to calibrate the inductor-capacitor (LC) resonance frequencies of the power transmitter(s) and the power receiver(s) in the resonant magnetic coupling wireless power transfer system to achieve the highest power transferred to the load and a high PTE.

A method for detecting useful signals in an overall signal. Each useful signal may be affected with a frequency drift. In the detection phase, frequency spectra for detecting the overall signal for multiple detection time windows are calculated and useful signals according to the detection frequency spectra are detected. In the estimation phase, for each useful signal detected: the frequency of the overall signal for multiple frequency drift values is reset. In the estimation phase, for each useful signal detected, a frequency spectrum is calculated for the estimation of the overall signal for each frequency drift value over an estimation time window having the useful signal detected and of a duration higher than the detection time window. In the estimation phase, for each useful signal detected, the frequency drift is estimated affecting the useful signal detected according to the estimation frequency spectra.

A method for detecting useful signals in an overall signal. Each useful signal may be affected with a frequency drift. In the detection phase, frequency spectra for detecting the overall signal for multiple detection time windows are calculated and useful signals according to the detection frequency spectra are detected. In the estimation phase, for each useful signal detected: the frequency of the overall signal for multiple frequency drift values is reset. In the estimation phase, for each useful signal detected, a frequency spectrum is calculated for the estimation of the overall signal for each frequency drift value over an estimation time window having the useful signal detected and of a duration higher than the detection time window. In the estimation phase, for each useful signal detected, the frequency drift is estimated affecting the useful signal detected according to the estimation frequency spectra.

Automatic frequency controllers, automatic frequency control methods, wireless communication devices, and/or wireless communication methods are provided. The automatic frequency controllers for correcting a frequency offset between a base station and a terminal includes at least one processor communicatively coupled to a memory and configured to execute computer-readable instructions stored in the memory to obtain a phase estimate from a reference signal received from the base station; classify a downlink channel as a High Speed Train (HST) channel or a non-HST channel based on the phase estimate; adjust a loop gain according to the classified downlink channel; calculate a phase error based on the phase estimate and the loop gain; correct the frequency offset using the phase error; and communicate with the base station after correcting the frequency offset.

Automatic frequency controllers, automatic frequency control methods, wireless communication devices, and/or wireless communication methods are provided. The automatic frequency controllers for correcting a frequency offset between a base station and a terminal includes at least one processor communicatively coupled to a memory and configured to execute computer-readable instructions stored in the memory to obtain a phase estimate from a reference signal received from the base station; classify a downlink channel as a High Speed Train (HST) channel or a non-HST channel based on the phase estimate; adjust a loop gain according to the classified downlink channel; calculate a phase error based on the phase estimate and the loop gain; correct the frequency offset using the phase error; and communicate with the base station after correcting the frequency offset.

A signal input from a microphone is A-D converted by an A-D converter, is frequency differentiated by a pre-emphasis circuit, and is input to a shift control circuit. The shift control circuit includes a limiter circuit, a phase shifter, and a harmonic suppressor. The limiter circuit performs amplitude limitation so as to limit the amplitude of the input control target signal to be equal to or less than a first threshold. The phase shifter shifts, for the control target signal having the amplitude limited, a phase of a frequency component within the predetermined frequency range. The harmonic suppressor suppresses, for the control target signal phase-shifted by the phase shifter, a frequency component equal to or greater than a second threshold, and outputs an information signal that is the control target signal having the frequency component of equal to or greater than the second threshold suppressed. The modulator performs frequency modulation on a carrier wave in accordance with the information signal. The transmitter produces a transmission signal from the frequency-modulated carrier wave, and transmits the transmission signal via an antenna.

A signal input from a microphone is A-D converted by an A-D converter, is frequency differentiated by a pre-emphasis circuit, and is input to a shift control circuit. The shift control circuit includes a limiter circuit, a phase shifter, and a harmonic suppressor. The limiter circuit performs amplitude limitation so as to limit the amplitude of the input control target signal to be equal to or less than a first threshold. The phase shifter shifts, for the control target signal having the amplitude limited, a phase of a frequency component within the predetermined frequency range. The harmonic suppressor suppresses, for the control target signal phase-shifted by the phase shifter, a frequency component equal to or greater than a second threshold, and outputs an information signal that is the control target signal having the frequency component of equal to or greater than the second threshold suppressed. The modulator performs frequency modulation on a carrier wave in accordance with the information signal. The transmitter produces a transmission signal from the frequency-modulated carrier wave, and transmits the transmission signal via an antenna.