  Improving resolution and sensitivity will widen possible medical applications
of magnetic particle imaging. Pulsed excitation promises such benefits, at the
cost of more complex hardware solutions and restrictions on drive field
amplitude and frequency. State-of-the-art systems utilize a sinusoidal
excitation to drive superparamagnetic nanoparticles into the non-linear part of
their magnetization curve, which creates a spectrum with a clear separation of
direct feed-through and higher harmonics caused by the particles response. One
challenge for rectangular excitation is the discrimination of particle and
excitation signals, both broad-band. Another is the drive-field sequence
itself, as particles that are not placed at the same spatial position, may
react simultaneously and are not separable by their signal phase or shape. To
overcome this potential loss of information in spatial encoding for high
amplitudes, a superposition of shifting fields and drive-field rotations is
proposed in this work. Upon close view, a system matrix approach is capable to
maintain resolution, independent of the sequence, if the response to pulsed
sequences still encodes information within the phase. Data from an Arbitrary
Waveform Magnetic Particle Spectrometer with offsets in two spatial dimensions
is measured and calibrated to guarantee device independence. Multiple sequence
types and waveforms are compared, based on frequency space image reconstruction
from emulated signals, that are derived from measured particle responses. A
resolution of 1.0 mT (0.8 mm for a gradient of (-1.25,\,-1.25,\,2.5) T/m) in x-
and y-direction was achieved and a superior sensitivity for pulsed sequences
was detected on the basis of reference phantoms.
