  We investigate the behavior of the directed current in one-dimensional
systems of Dirac fermions driven by local periodic potentials in the forward as
well in backscattering channels. We treat the problem with Keldysh
non-equilibrium Green's function formalism. We present the exact solution for
the case of an infinite wire and show that in this case the dc current vanishes
identically. We also investigate a confined system consistent in an annular
arrangement coupled to a particle reservoir. We present a perturbative
treatment that allows for the analytical expressions of the dc current in the
lowest order of the amplitudes of the potential. We also present results
obtained from the exact numerical solution of the problem.
