  Inevitable interferences exist for the SAR system, adversely affecting the
imaging quality. However, current analysis and suppression methods mainly focus
on the far-field situation. Due to different sources and characteristics of
interferences, they are not applicable in the near field. To bridge this gap,
in the first time, analysis and the suppression method of interferences in
near-field SAR are presented in this work. We find that echoes from both the
nadir points and the antenna coupling are the main causes, which have the
constant-time-delay feature. To characterize this, we further establish an
analytical model. It reveals that their patterns in 1D, 2D and 3D imaging
results are all comb-like, while those of targets are point-like. Utilizing
these features, a suppression method in image domain is proposed based on
low-rank reconstruction. Measured data are used to validate the correctness of
our analysis and the effectiveness of the suppression method.
