  Motion of an atomic ensemble trapped into a deep optical lattice is
considered. We propose a novel approach to construct an atomic ratchet by
superimposing two additional lattices whose amplitudes are small and subjected
to broadband modulation. The broadband modulation is modeled by means of
harmonic noise. Directed atomic transport occurs with the properly chosen phase
shift between the signals modulating the amplitudes of the additional lattices.
It is shown that efficiency of the ratchet depends non-monotonously on the
parameter determining the spectral width of modulating signals.
