Accelerating Digital Focusing Method for Millimeter-Wave Holographic Imaging With Arbitrary MIMO Array

Due to the fast scanning capabilities and sparse arrangement, multiple-input multiple-output (MIMO) arrays have gained widespread use in millimeter-wave (MMW) holographic imaging. The traditional image reconstruction for arbitrary MIMO arrays relies on the digital focusing (DF) method, which involves extensive phase compensating calculations. To overcome this challenge, we present an accelerated DF method based on dimension reduction (DR) and fast Fourier transform (FFT), which reduces computational complexity from
$O(N^{6})$
to
$O(N^{3}\log N)$
. Simulation and measurement experimental results demonstrate that our proposed method can achieve a 109-fold speedup for cross-orthogonal array scanning simulation and a 433-fold speedup for 1-D MIMO array scanning experiment compared to the original DF method while containing almost no image quality loss.