  Through a linear stability analysis, we investigate the effectiveness of a
noninvasive feedback control scheme aimed at stabilizing traveling wave
solutions of the one-dimensional complex Ginzburg Landau equation (CGLE) in the
Benjamin-Feir unstable regime. The feedback control is a generalization of the
time-delay method of Pyragas, which was proposed by Lu, Yu and Harrison in the
setting of nonlinear optics. It involves both spatial shifts, by the wavelength
of the targeted traveling wave, and a time delay that coincides with the
temporal period of the traveling wave. We derive a single necessary and
sufficient stability criterion which determines whether a traveling wave is
stable to all perturbation wavenumbers. This criterion has the benefit that it
determines an optimal value for the time-delay feedback parameter. For various
coefficients in the CGLE we use this algebraic stability criterion to
numerically determine stable regions in the (K,rho) parameter plane, where rho
is the feedback parameter associated with the spatial translation and K is the
wavenumber of the traveling wave. We find that the combination of the two
feedbacks greatly enlarges the parameter regime where stabilization is
possible, and that the stability regions take the form of stability tongues in
the (K,rho)--plane. We discuss possible resonance mechanisms that could account
for the spacing with K of the stability tongues.
