Adaptive Background Clutter Mitigation for Millimeter Wave MIMO Imaging

To suppress background clutter in short-range millimeter wave multiple-input multiple-output (MIMO) imaging, an adaptive and cost-efficient approach is proposed based on the availability of the background observation. By analyzing the origins of the background clutter, gain variation, and blocking effect are identified as the primary culprits responsible for the background clutter variation, which are treated separately in the proposed method. The gain variation is compensated with an adaptive power weighting (APW) procedure, where the gain variance is accurately and rapidly measured using the short-range profile segment associated with the interelement direct coupling. The clutter residual due to the blocking effect after APW is further removed by the combination of two zero-thresholding processes and coherence-factor-based image enhancement. The proposed method entails relatively light computational burden at the cost of acceptable memory increment, and is, thus, more amenable to real-time imaging requirement. Both simulations and experimental imaging tests on an MIMO array demonstrate the effectiveness and cost-efficiency of the proposed approach.