ACCURATE POWER SPECTRUM ESTIMATION OF A DAMPED SINUSOIDAL SIGNAL IN LOW SNR CASES BASED ON A NEWLY DEFINED TRANSFER-FUNCTION

This paper is concerned with a method to estimate the power spectrum o f a periodic damped sinusoidal signal contaminated by high-level noise components when there are fluctuations in the period. A correlation b etween two spectral components exists at and around the resonant frequ ency of a damped sinusoidal signal. By using this property, the author s introduce a new transfer function defined from the resonant frequenc y component to every other component around the resonant frequency to estimate the power spectrum of the damped sinusoidal signal. Since it can be assumed that there is no correlation between these two differen t frequencies for the noise components, the noise components in the cr oss spectrum at the two different frequencies decrease with the averag ing operation. Consequently, the power spectrum of the damped sinusoid al signal is accurately estimated from the observed signals, even if t he signal-to-noise ratio (SNR) is very low. The proposed method develo ped here is satisfactorily confirmed by simulation experiments. This m ethod is further applied to the estimation of the power spectra of the vibration signals radiated from normal and defective automobile engin es.