Analysis and Calibration of Spatially Variant Wavenumber Spectrum in Near-Field SAR Imaging

Under the near-field condition, the wavenumber spectrum is spatially variant, and its center and size are both related to the target positions, which increases the difficulty of imaging processing and sidelobe suppression. In this article, a novel two-step spectrum calibration method is proposed to eliminate the correlation between the wavenumber spectrum and the target position. This method first multiplies the imaging results by a phase compensation term to shift the spectrum centers of all targets to the origin. Then an image deformation technique is introduced to eliminate the difference in the offset angle of the wavenumber spectrum. The compensated wavenumber spectra have the same center and are symmetrical about the coordinate axis. Experimental results on simulation data verify that the proposed method can effectively eliminate the spatial variance of the wavenumber spectrum and realize the compression and recovery of the wavenumber spectrum.