  Orthogonal frequency-division multiplexing (OFDM) is a promising waveform
candidate for future joint sensing and communication systems. It is well known
that the OFDM waveform is vulnerable to in-phase and quadrature-phase (IQ)
imbalance, which increases the noise floor in a range-Doppler map (RDM). A
state-of-the-art method for robustifying the OFDM waveform against IQ imbalance
avoids an increased noise floor, but it generates additional ghost objects in
the RDM [1]. A consequence of these additional ghost objects is a reduction of
the maximum unambiguous range. In this work, a novel OFDM-based waveform robust
to IQ imbalance is proposed, which neither increases the noise floor nor
reduces the maximum unambiguous range. The latter is achieved by shifting the
ghost objects in the RDM to different velocities such that their range
variations observed over several consecutive RDMs do not correspond to the
observed velocity. This allows tracking algorithms to identify them as ghost
objects and eliminate them for the follow-up processing steps. Moreover, we
propose complete communication systems for both the proposed waveform as well
as for the state-of-the-art waveform, including methods for channel estimation,
synchronization, and data estimation that are specifically designed to deal
with frequency selective IQ imbalance which occurs in wideband systems. The
effectiveness of these communication systems is demonstrated by means of bit
error ratio (BER) simulations.
