  This paper describes the procedure to estimate the parameters in mean
reversion processes with functional tendency defined by a periodic continuous
deterministic function, expressed as a series of truncated Fourier. Two phases
of estimation are defined, in the first phase through Gaussian techniques using
the Euler-Maruyama discretization, we obtain the maximum likelihood function,
that will allow us to find estimators of the external parameters and an
estimation of the expected value of the process. In the second phase, a
reestimate of the periodic functional tendency with it's parameters of phase
and amplitude is carried out, this will allow, improve the initial estimation.
Some experimental result using simulated data sets are graphically illustrated.
