  We show that combination of a linearly polarized resonant microwave field and
a parallel static electric field may be used to create a non-dispersive
electronic wavepacket in Rydberg atoms. The static electric field allows for
manipulation of the shape of the elliptical trajectory the wavepacket is
propagating on. Exact quantum numerical calculations for realistic experimental
parameters show that the wavepacket evolving on a linear orbit can be very
easily prepared in a laboratory either by a direct optical excitation or by
preparing an atom in an extremal Stark state and then slowly switching on the
microwave field. The latter scheme seems to be very resistant to experimental
imperfections. Once the wavepacket on the linear orbit is excited, the static
field may be used to manipulate the shape of the orbit.
