Aliasing Artifacts Suppression in MIMO Millimeter-Wave Imaging Systems Based on K-Space Analysis

Abstract

This paper focuses on dealing with aliasing artifacts in millimeter-wave imaging systems. To address the challenges and complexities of designing multi-static arrays, sparse arrangements are utilized in practical imaging systems. Depending on the arrangement of antennas, such arrays may present severe aliasing artifacts. Some techniques have already been introduced to tackle such artifacts and enhance the image quality. These techniques may either distort the target image by causing some loss in parts of the image, impose high computational/system costs or suffer from the lack of generalizability. One of these techniques uses non-uniform arrays. Such arrays are designed by optimizing the point spread function (PSF). The PSF is a suitable representative of the system’s performance provided that the system is shift-invariant. Since non-uniform arrays are shift-variant, these techniques are unreliable, especially in the case of off-center targets. As a consequence, there are no frameworks to design non-uniform arrays on a reliable basis to suppress aliasing artifacts in the whole region of interest (ROI). To address this issue, based on the k-space analysis of aliasing in multi-static arrays and non-uniform Fourier transform concept, we propose a small random displacement to be applied to antennas’ location in sparse periodic arrays. This displacement prevents the aliasing components from coherently accumulating. Nevertheless, due to the imposed non-uniformity, it is impossible to use FFT-based algorithms in this case. A subsequent resampling or the use of non-uniform FFT can address this problem. The provided simulations and experimental measurements show that the proposed method can efficiently lower the peak level of aliasing artifacts by around 3dB compared to sparse periodic arrays. So, the proposed method can be used as an effective way to suppress aliasing artifacts in real-time multi-static millimeter-wave imaging systems.