Instantaneous spectral estimation of nonstationary signals

In this paper, new methods are proposed to estimate a nonstationary spectrum based on the covariance method (COV) and maximum entropy method (MEM). First, their evaluation functions are improved by an instantaneous expression. Secondly, the 2-D spectrum is defined as the spectrum frequency of the variation of the conventional spectrum, and band-limitation is achieved on the 2-D spectrum. The instantaneous covariance method (ICOV) and instantaneous maximum entropy method (IMEM) are newly derived from the above procedure. In this paper, the Wigner-Boashash method is also derived from the same viewpoint. IMEM was applied to analyze nonstationary signals of automobile vibration and speech signals