  Multiple-input-multiple-output (MIMO) millimeter-wave (mmWave) sensors for
synthetic aperture radar (SAR) and inverse SAR (ISAR) address the fundamental
challenges of cost-effectiveness and scalability inherent to near-field
imaging. In this paper, near-field MIMO-ISAR mmWave imaging systems are
discussed and developed. The rotational ISAR (R-ISAR) regime investigated in
this paper requires rotating the target at a constant radial distance from the
transceiver and scanning the transceiver along a vertical track. Using a 77GHz
mmWave radar, a high resolution three-dimensional (3-D) image can be
reconstructed from this two-dimensional scanning taking into account the
spherical near-field wavefront. While prior work in literature consists of
single-input-single-output circular synthetic aperture radar (SISO-CSAR)
algorithms or computationally sluggish MIMO-CSAR image reconstruction
algorithms, this paper proposes a novel algorithm for efficient MIMO 3-D
holographic imaging and details the design of a MIMO R-ISAR imaging system. The
proposed algorithm applies a multistatic-to-monostatic phase compensation to
the R-ISAR regime allowing for use of highly efficient monostatic algorithms.
We demonstrate the algorithm's performance in real-world imaging scenarios on a
prototyped MIMO R-ISAR platform. Our fully integrated system, consisting of a
mechanical scanner and efficient imaging algorithm, is capable of pairing the
scanning efficiency of the MIMO regime with the computational efficiency of
single pixel image reconstruction algorithms.
