Fourth-order spectra of filtered intensity modulated sinusoids
Roger F. Dwyer · The Journal of the Acoustical Society of America · 1990
The sinusoidal frequency of a propagating intensity-modulated sinusoidal signal can be extracted by fourth-order spectra. This has been demonstrated in an underwater transmit/receive experiment. The physical reason for this result is that fourth-order spectra are not degraded by the covariance of the modulating function. Moreover, a special case of the fourth-order cumulant spectrum is independent of the covariance and only depends on the variance of the modulating function. The current study concentrates on the convergence properties of fourth-order spectra and on properties of filtered intensity-modulated sinusoids. The convergence properties are given in terms of the mean and variance of the fourth-order moment and fourth-order cumulant estimators. Then, the properties of filtered intensity-modulated sinusoids are discussed for both fourth-order spectra and the special case.