A frequency detection circuit includes: a first signal source for outputting a first clock signal; a second signal source for outputting a second clock signal having the same frequency as but a different phase from those of the first clock signal; a first sample hold circuit for undersampling a reception signal using the first clock signal; a second sample hold circuit for undersampling the reception signal using the second clock signal; and a frequency calculating circuit for calculating the frequency of the reception signal using a phase difference between output signals of the first sample hold circuit and the second sample hold circuit.

A device includes a first oscillator, a second oscillator and a frequency comparison block. The first oscillator includes a first LC tank circuit and is designed to generate first sustained oscillations at a first resonant frequency. The second oscillator includes a second LC tank circuit and is designed to generate second sustained oscillations at a second resonant frequency. The frequency comparison block is designed to perform a comparison of the frequencies of the second sustained oscillations and the first sustained oscillations to determine a change in inductance in one of a first inductor of the first LC tank circuit and a second inductor of the second LC tank circuit. One of the oscillators serves as a reference oscillator, and enables determination of the change in inductance to be immune to changes in environmental conditions.

A device includes a first oscillator, a second oscillator and a frequency comparison block. The first oscillator includes a first LC tank circuit and is designed to generate first sustained oscillations at a first resonant frequency. The second oscillator includes a second LC tank circuit and is designed to generate second sustained oscillations at a second resonant frequency. The frequency comparison block is designed to perform a comparison of the frequencies of the second sustained oscillations and the first sustained oscillations to determine a change in inductance in one of a first inductor of the first LC tank circuit and a second inductor of the second LC tank circuit. One of the oscillators serves as a reference oscillator, and enables determination of the change in inductance to be immune to changes in environmental conditions.

Conventional frequency detection circuits have a disadvantage that the circuit scale increases as the frequency of a reception signal to be detected increases.

A frequency detection circuit includes: a first signal source for outputting a first clock signal; a second signal source for outputting a second clock signal having the same frequency as but a different phase from those of the first clock signal; a first sample hold circuit for undersampling a reception signal using the first clock signal; a second sample hold circuit for undersampling the reception signal using the second clock signal; and a frequency calculating circuit for calculating the frequency of the reception signal using a phase difference between output signals of the first sample hold circuit and the second sample hold circuit.

Provided a method comprising: obtaining waveform data sets of a periodic electric waveform signal, with a length set to one cycle time; calculating a frequency spectrum for each waveform data set; extracting and separating odd and even frequency harmonics to create odd and even frequency harmonic matrices on which a canonical correlation analysis (CCA) being applied to obtain CCA features; performing linear transformation on the CCA features to obtain linear transformed features; generating a model based on the linear transformed features; performing magnitude quantization of frequency spectrums of waveform data sets to identify normal and anomalous waveform signals.

Provided are an apparatus and a method for measuring a frequency of a broadband signal by using low-speed ADCs having sub-Nyquist sampling rates. A plurality of channels each including a low-speed ADC having a sub-Nyquist sampling rate (e.g. sampling frequency from several MHz to hundreds of MHz) are provided, and the frequency of an input signal corresponding to a combination of frequencies calculated through the respective channels is estimated. Therefore, as the number of channels increases, the range of measurable frequencies may be extended.

Provided are an apparatus and a method for measuring a frequency of a broadband signal by using low-speed ADCs having sub-Nyquist sampling rates. A plurality of channels each including a low-speed ADC having a sub-Nyquist sampling rate (e.g. sampling frequency from several MHz to hundreds of MHz) are provided, and the frequency of an input signal corresponding to a combination of frequencies calculated through the respective channels is estimated. Therefore, as the number of channels increases, the range of measurable frequencies may be extended.

A digital measurement system includes an oscillator, a mixer, and a controller coupled to each other. The oscillator provides a reference signal having a second frequency. The mixer generates a down-converted signal based on the output signal and the reference signal. The controller then determines a characteristic of the output signal (e.g., frequency or phase) based on the down-converted signal. An analog measurement system includes a filter having a center frequency, a rectifier, and a controller. The filter filters the output signal and the rectifier rectifies the filtered signal. The controller samples the rectified signal and determines a characteristic of the output signal based on the level of the rectified signal. The reference signal controller may adjust a characteristic of the output signal based on the determined frequency and/or phase of the output signal.

Provided a method comprising: obtaining waveform data sets of a periodic electric waveform signal, with a length set to one cycle time; calculating a frequency spectrum for each waveform data set; extracting and separating odd and even frequency harmonics to create odd and even frequency harmonic matrices on which a canonical correlation analysis (CCA) being applied to obtain CCA features; performing linear transformation on the CCA features to obtain linear transformed features; generating a model based on the linear transformed features; performing magnitude quantization of frequency spectrums of waveform data sets to identify normal and anomalous waveform signals.

A digital measurement system includes an oscillator, a mixer, and a controller coupled to each other. The oscillator provides a reference signal having a second frequency. The mixer generates a down-converted signal based on the output signal and the reference signal. The controller then determines a characteristic of the output signal (e.g., frequency or phase) based on the down-converted signal. An analog measurement system includes a filter having a center frequency, a rectifier, and a controller. The filter filters the output signal and the rectifier rectifies the filtered signal. The controller samples the rectified signal and determines a characteristic of the output signal based on the level of the rectified signal. The reference signal controller may adjust a characteristic of the output signal based on the determined frequency and/or phase of the output signal.