  Time-delayed feedback methods can be used to control unstable periodic orbits
as well as unstable steady states. We present an application of extended time
delay autosynchronization introduced by Socolar et al. to an unstable focus.
This system represents a generic model of an unstable steady state which can be
found for instance in a Hopf bifurcation. In addition to the original
controller design, we investigate effects of control loop latency and a
bandpass filter on the domain of control. Furthermore, we consider coupling of
the control force to the system via a rotational coupling matrix parametrized
by a variable phase. We present an analysis of the domain of control and
support our results by numerical calculations.
