1,721,196 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 textEstensione delle Prestazioni TDR per il Monitoraggio Qualitativo in Liquidi Industriali tramite un Approccio Combinato nel Dominio del Tempo e della Frequenza
No full textMiglioramento delle prestazioni di stimatori spettrali con l’impiego di medie non lineari
No full textProgetto e realizzazione di uno strumento virtuale intelligente finalizzato all’analisi spettrale di segnali non-sinusoidali rumorosi
No full textStudio dell’influenza del rumore nelle misure via PWD di frequenza e ampiezza istantanea di segnali transitori
No full text
Flat-top smoothing of periodograms for improvement of accuracy in estimating power spectra with the Welch's method
No full textThe main problem with the test engineer is often involved when approaching spectral estimates through FFT-based measuring systems is to control the bias and variance in the periodogram. This trade-off is particularly difficult to be reached as different parameters (type of taper for spectral smoothing, the length of the observation interval, noise level and so on) can bring to opposite results: usually, a decreasing of bias yields an increasing of variance of the estimate. The authors obtained, in previous papers, quantitative expressions for the normalized bias and standard errors when flat-top tapering and frequency averagings are employed. In this paper the experimental validations of such results are shown and the performance of a Virtual Instrument (VI) carrying out spectral analyses according to the explained techniques and realized in OOP (Object Oriented Programming language) is highlighted
- …
