Low-Bandwidth mmW Grating Lobes Suppression Method for 2-D Sparse MIMO Array Imaging

In millimeter-wave (mmW) sparse multiple-input–multiple-output (MIMO) array imaging, excessive element spacing produces grating lobes, resulting in ghost artifacts, especially in low-bandwidth conditions. In this letter, by transforming the point spread function of a 2-D boundary array into Chebyshev polynomials and analyzing its characteristics, a method for suppressing both grating lobes and sidelobes for 2-D sparse boundary MIMO array imaging is proposed. Sidelobe and grating lobe energy is reduced by a frequency enhanced coherence factor through frequency and transceiver channels changes, resulting in improved image quality at first. The maximum sliding square error energy compensation term is then applied to eliminate grating lobes while preserving main lobe characteristics through subband image analysis. Simulations and experiments validate the method's effectiveness.