  The problem of joint estimation of power spectrum and modulation from
realizations of frequency modulated stationary wideband signals is considered.
The study is motivated by some specific signal classes from which departures to
stationarity can carry relevant information and has to be estimated. The
estimation procedure is based upon explicit modeling of the signal as a
wideband stationary Gaussian signal, transformed by time-dependent, smooth
frequency modulation. Under such assumptions, an approximate expression for the
second order statistics of the transformed signal's Gabor transform is
obtained, which leads to an approximate maximum likelihood estimation
procedure. The proposed approach is validated on numerical simulations.
