  We apply the Small Tip-Angle Approximation in the Toggling Frame in order to
analytically design robust pulses against resonance offsets for state to state
transfer in two-level quantum systems. We show that a broadband or a local
robustness up to an arbitrary order can be achieved. We provide different
control parameterizations to satisfy experimental constraints and limitations
on the amplitude or energy of the pulse. A comparison with numerical optimal
solutions is made.
