1,721,138 research outputs found
Optimal characterization of time-frequency measurements on distorted nonstationary signals
No full textThe problem of estimating the instantaneous frequency and amplitude for nonstationary noisy signal is addressed. An analysis of the casual errors due to the presence of noise is given for Wigner-Ville distribution; particularly, the theoretical bias for instantaneous frequency and amplitude is carried out. The Authors have already developed suitable interpolation techniques for both STFT and SPWD distributions, with the aim of reducing the incorrect spectral estimates caused by frequency variation and lack in synchronization. So high levels of accuracy, flexibility and efficiency, have been obtained even if heavily nonstationary components were present. Now, the research carried on with the analysis of the stochastical disturbance, by examining closely their effects on the methods proposed, having the object of developing a modified version that produce high levels of accuracy also when only noisy input data are available. The final aim is to implement the suggest techniques in a dedicated digital instrument, to perform accurate time-frequency analysis of nonstationary distorted noisy signals
Interpolazione delle distribuzioni tempo-frequenza per misure di grandezze elettriche non stazionarie
No full text
Studio dell’influenza del rumore nelle misure via PWD di frequenza e ampiezza istantanea di segnali transitori
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Interpolated smoothed Pseudo Wigner-Ville Distribution for accurate spectrum analysis
No full textThis paper deals with a new application of the time-domain windowed (smoothed version) of the pseudo Wigner-Ville distribution (PWD), that can be easily implemented in a dedicate digital instrument to be used as a spectral analyzer for time-frequency analysis of nonstationary signals. New computational algorithms are studied and developed to attain high time-frequency resolution, accuracy, flexibility and computational efficiency, Particularly, to reduce the negative effects due to leakage during frequency changes, a new interpolation formula is derived by using the windowing theory, The suggested technique allows the users to perform optimal evaluations of the instantaneous amplitudes and frequencies of analyzed signals
Definition and measurement of a new electrical power quality index for power system management purposes
No full textThis work deals with the purpose of a new measurement methodology and a new qualità index to evaluate quality of the signal, particularly of electrical ones, valid also when these signal are non-stationary. A new quality index, named Wavelet Harmonic Distortion (WHD), is here suggested, taking origin from the theory of the Wavelet Transform, very useful to on-line evaluate the well-known Total Harmonic Distortion (THD) of the voltage and current signals relevant to power systems
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