  A new type of delocalization induced by coherent harmonic perturbations in
one-dimensional Anderson-localized disordered systems is investigated. With
only a few $M$ frequencies a normal diffusion is realized, but the transition
to localized state always occurs as the perturbation strength is weakened below
a critical value. The nature of the transition qualitatively follows the
Anderson transition (AT) if the number of degrees of freedom $M+1$ is regarded
as the spatial dimension $d$, but the critical dimension is not $d=M+1-2$ of
the ordinary AT but $d=3$.
