  The use of the Wigner function for the study of quantum transport in open
systems present severe criticisms. Some of the problems arise from the
assumption of infinite coherence length of the electron dynamics outside the
system of interest. In the present work the theory of the Wigner function is
revised assuming a finite coherence length. A new dynamical equation is found,
corresponding to move the Wigner momentum off the real axis, and a numerical
analysis is performed for the case of study of the onedimensional potential
barrier.
