A frequency spectrum detection system including: a frequency-scan light source, a phase modulator, an optical filter, an optical fiber, a photodetector, a power divider, an electric amplifier, a combiner, an electric filter, and an oscilloscope. The frequency-scan light source, the phase modulator, the optical filter, the photodetector, and the electric amplifier form a ring-shaped optoelectronic oscillator resonant cavity, which is configured to generate a frequency-scan signal. The combiner is configured to receive a signal to be measured. The phase modulator is configured to modulate the combined electrical signal onto a frequency-scan optical signal. The optical filter is configured to selectively attenuate or amplify one sideband of double sidebands of the double-sideband phase-modulated optical signal. The photodetector is configured to detect a signal filtered by the optical filter.

A frequency spectrum detection system including: a frequency-scan light source, a phase modulator, an optical filter, an optical fiber, a photodetector, a power divider, an electric amplifier, a combiner, an electric filter, and an oscilloscope. The frequency-scan light source, the phase modulator, the optical filter, the photodetector, and the electric amplifier form a ring-shaped optoelectronic oscillator resonant cavity, which is configured to generate a frequency-scan signal. The combiner is configured to receive a signal to be measured. The phase modulator is configured to modulate the combined electrical signal onto a frequency-scan optical signal. The optical filter is configured to selectively attenuate or amplify one sideband of double sidebands of the double-sideband phase-modulated optical signal. The photodetector is configured to detect a signal filtered by the optical filter.

A wideband device for the spectral analysis of a signal of interest includes a source designed to generate the signal of interest; an optical splitter element designed to spatially split the signal of interest into a first signal and a second signal; a first frequency-shifting optical cavity comprising a first frequency shifter designed to shift the optical frequency of the first signal by a first frequency f.sub.1 per round trip in the first cavity, the first cavity having a first trip time .sub.1; a second frequency-shifting optical cavity comprising a second frequency shifter designed to shift the optical frequency of the second signal by a second frequency f.sub.2 per round trip in the second cavity, the second cavity having a second trip time .sub.2; the first and the second optical cavity being designed such that a maximum number of round trips of the signal in the first and the second cavity is equal to predetermined N; a detector designed to coherently detect the first signal transmitted by the first cavity and the second signal transmitted by the second cavity and generate a photocurrent proportional to a luminous intensity detected by the detector, an analog low-pass filter designed to filter frequencies of the photocurrent that are lower than min (f.sub.12/; f.sub.2/2) a processor configured to compute a square modulus of the photocurrent filtered by the low-pass filter, from which a temporal representation of frequency information of the signal of interest is determined.

A wideband device for the spectral analysis of a signal of interest includes a source designed to generate the signal of interest; an optical splitter element designed to spatially split the signal of interest into a first signal and a second signal; a first frequency-shifting optical cavity comprising a first frequency shifter designed to shift the optical frequency of the first signal by a first frequency f.sub.1 per round trip in the first cavity, the first cavity having a first trip time .sub.1; a second frequency-shifting optical cavity comprising a second frequency shifter designed to shift the optical frequency of the second signal by a second frequency f.sub.2 per round trip in the second cavity, the second cavity having a second trip time .sub.2; the first and the second optical cavity being designed such that a maximum number of round trips of the signal in the first and the second cavity is equal to predetermined N; a detector designed to coherently detect the first signal transmitted by the first cavity and the second signal transmitted by the second cavity and generate a photocurrent proportional to a luminous intensity detected by the detector, an analog low-pass filter designed to filter frequencies of the photocurrent that are lower than min (f.sub.12/; f.sub.2/2) a processor configured to compute a square modulus of the photocurrent filtered by the low-pass filter, from which a temporal representation of frequency information of the signal of interest is determined.

Fractional Fourier Transform (FrFT)-based spectrum analyzers and spectrum analysis techniques are disclosed. Rather than using the standard Fast Fourier Transform (FFT), the FrFT may be used to view the signal content contained in a particular bandwidth. Usage of the FrFT in place of the frequency or time domain allows viewing of the signal in different dimensions, where spectral features of interest, or signal content, may appear where they were not visible in these domains before. This may allow signals to be identified and viewed in any domain within the continuous time-frequency plane, and may significantly enhance the ability to detect and extract signals that were previously hidden under interference and/or noise, provide or enhance the ability to extract signals from a congested environment, and enable operation in a signal-dense environment.

Fractional Fourier Transform (FrFT)-based spectrum analyzers and spectrum analysis techniques are disclosed. Rather than using the standard Fast Fourier Transform (FFT), the FrFT may be used to view the signal content contained in a particular bandwidth. Usage of the FrFT in place of the frequency or time domain allows viewing of the signal in different dimensions, where spectral features of interest, or signal content, may appear where they were not visible in these domains before. This may allow signals to be identified and viewed in any domain within the continuous time-frequency plane, and may significantly enhance the ability to detect and extract signals that were previously hidden under interference and/or noise, provide or enhance the ability to extract signals from a congested environment, and enable operation in a signal-dense environment.

A fault arc signal detection method using a convolutional neural network, comprising: enabling a sampling signal subjected to analog-digital conversion to respectively pass through three different band-pass filters; respectively extracting a time-domain feature and a frequency-domain feature from a half wave output of each filter; constructing a two-dimensional feature matrix by means of extracted time-frequency feature vectors from the output of each filter, and stacking the feature matrices corresponding the outputs of the three filters to construct a three-dimensional matrix for each half wave; and processing a multi-channel feature matrix by using a multi-channel two-dimensional convolutional neural network, and determining, according to the output result of the neural network, whether the half wave is an arc. The detection method based on the convolutional neural network has higher accuracy and reliability in recognizing a fault arc half wave, can implement targeted training for different load conditions, and is self-adaptive.

A fault arc signal detection method using a convolutional neural network, comprising: enabling a sampling signal subjected to analog-digital conversion to respectively pass through three different band-pass filters; respectively extracting a time-domain feature and a frequency-domain feature from a half wave output of each filter; constructing a two-dimensional feature matrix by means of extracted time-frequency feature vectors from the output of each filter, and stacking the feature matrices corresponding the outputs of the three filters to construct a three-dimensional matrix for each half wave; and processing a multi-channel feature matrix by using a multi-channel two-dimensional convolutional neural network, and determining, according to the output result of the neural network, whether the half wave is an arc. The detection method based on the convolutional neural network has higher accuracy and reliability in recognizing a fault arc half wave, can implement targeted training for different load conditions, and is self-adaptive.

The invention relates to a device for the spectral analysis of an electromagnetic measurement signal using an optoelectronic mixer, wherein the optoelectronic mixer is designed to generate the electrical superimposition signal by superimposing the electromagnetic measurement signal and a reference signal with at least one known frequency (fo). The device comprises the following features: a signal input for receiving an electrical superimposition signal from the optoelectronic mixer, a low-pass filter, a rectifier, and a read-out unit. The low-pass filter is designed to generate a filtered superimposition signal from the electrical superimposition signal by filtering out frequency portions above an upper cutoff frequency (fG). The rectifier is designed to generate a rectified superimposition signal from the filtered superimposition signal. The read-out unit is designed to determine a match of the known frequency (fo) of the reference signal with the electromagnetic measurement signal based on the rectified overlay signal.

The invention relates to a device for the spectral analysis of an electromagnetic measurement signal using an optoelectronic mixer, wherein the optoelectronic mixer is designed to generate the electrical superimposition signal by superimposing the electromagnetic measurement signal and a reference signal with at least one known frequency (fo). The device comprises the following features: a signal input for receiving an electrical superimposition signal from the optoelectronic mixer, a low-pass filter, a rectifier, and a read-out unit. The low-pass filter is designed to generate a filtered superimposition signal from the electrical superimposition signal by filtering out frequency portions above an upper cutoff frequency (fG). The rectifier is designed to generate a rectified superimposition signal from the filtered superimposition signal. The read-out unit is designed to determine a match of the known frequency (fo) of the reference signal with the electromagnetic measurement signal based on the rectified overlay signal.