A wideband spectrum analyzer is disclosed that has good image suppression and dynamic range. The wideband spectrum analyzer includes at least one signal input, and at least one signal channel with a first filter module and a second filter module. The first filter module and the second filter module are connected with the at least one signal input downstream of the at least one signal input in a series connection. The first filter module includes first switches. The first filter module includes several different highpass filters being arranged in a parallel connection. The first switches are configured to selectively connect one of the highpass filters with an input of the first filter module and an output of the first filter module. The second filter module includes second switches. The second filter module includes several different lowpass filters being arranged in a parallel connection. The second switches are configured to selectively connect one of the lowpass filters with an input of the second filter module and an output of the second filter module.

Embodiments of the present disclosure describe frequency detection techniques for detecting power irregularities. These irregularities may include variations or abnormalities in switched-mode power supply circuit switching behavior, power spikes, and/or output oscillations. The frequency detection techniques may compare different frequency components of the power signal to detect irregularities.

A method for correcting a time-dependent measurement signal generated by means of an electric motor coupled on the output side to a transmission with regard to the influence of a variable output load and a variable rotational speed includes: tapping a time-varying measurement signal which is dependent on a torque of the motor transmission unit; generation of a useful signal, which is free of any DC component, from the measurement signal; interval-by-interval determination of RMS values from the measurement signal; generation of a load-corrected useful signal by an interval-by-interval division of the useful signal, which is free of any DC component, by the interval-specific RMS values; time-resolved determination of the rotational frequency of the motor from the measurement signal; scaling the load-corrected useful signal to the mean rotational frequency to generate a corrected measurement signal, and, use of the corrected measurement signal for fault detection of the motor transmission unit.

A method for correcting a time-dependent measurement signal generated by means of an electric motor coupled on the output side to a transmission with regard to the influence of a variable output load and a variable rotational speed includes: tapping a time-varying measurement signal which is dependent on a torque of the motor transmission unit; generation of a useful signal, which is free of any DC component, from the measurement signal; interval-by-interval determination of RMS values from the measurement signal; generation of a load-corrected useful signal by an interval-by-interval division of the useful signal, which is free of any DC component, by the interval-specific RMS values; time-resolved determination of the rotational frequency of the motor from the measurement signal; scaling the load-corrected useful signal to the mean rotational frequency to generate a corrected measurement signal, and, use of the corrected measurement signal for fault detection of the motor transmission unit.

A method, an apparatus and a system to measure nonlinear related parameters of a nonlinear device. The apparatus comprises a memory and a processor coupled to the memory to control execution of a process to: generate a first signal according to a signal to be measured, the first signal and the signal to be measured having a signal probability distribution that is same, and the first signal having at least one notch frequency; and calculate, according to an output signal of the nonlinear device when the first signal is input into the nonlinear device, nonlinear related parameters of the nonlinear device when the signal to be measured is transmitted.

A method, an apparatus and a system to measure nonlinear related parameters of a nonlinear device. The apparatus comprises a memory and a processor coupled to the memory to control execution of a process to: generate a first signal according to a signal to be measured, the first signal and the signal to be measured having a signal probability distribution that is same, and the first signal having at least one notch frequency; and calculate, according to an output signal of the nonlinear device when the first signal is input into the nonlinear device, nonlinear related parameters of the nonlinear device when the signal to be measured is transmitted.

A method for partial discharge recognition in high voltage applications and a high voltage unit using the method, includes the steps of detecting a signal, transforming the signal from time to frequency domain, cutting frequencies above a defined threshold, and retransform the truncated signal from frequency to time domain. The information content of detected and truncated signals is determined and compared.

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 method for monitoring the state of an electric machine includes determining within a defined frequency range, for example in a spectrogram of a current amplitude, a frequency position where a current amplitude has a maximum at the frequency position and where a phase relationship between a current vector and a voltage vector or between two current vectors is located in a predefined interval. The determined frequency position is characteristic; of the state of the electric machine.