  Millimeter-wave (MMW) imaging has a wide prospect in application of concealed
weapons detection. We propose a circular-arc multiple-input multiple-output
(MIMO) array scheme with uniformly spaced transmit and receive antennas along
the horizontal-arc direction, while scanning along the vertical direction. The
antenna beams of the circular-arc MIMO array can provide more uniform coverage
of the imaging scene than those of the linear or planar MIMO arrays. Further, a
near-field three-dimensional (3-D) imaging algorithm, based on the spatial
frequency domain processing, is presented with analysis of sampling criteria
and resolutions. Numerical simulations, as well as comparisons with the
back-projection (BP) algorithm, are provided to show the efficacy of the
proposed approach.
