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

This article focuses on dealing with aliasing artifacts in millimeter-wave imaging systems. To address the challenges and complexities of designing multistatic 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 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 nonuniform 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 nonuniform 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 nonuniform 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 multistatic arrays and nonuniform Fourier transform concept, we propose a small random displacement to be applied to antennas' location in sparse periodic arrays (SPAs). This displacement prevents the aliasing components from coherently accumulating. Nevertheless, due to the imposed nonuniformity, it is impossible to use FFT-based algorithms in this case. A subsequent resampling or the use of nonuniform 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 3 dB compared with SPAs. So, the proposed method can be used as an effective way to suppress aliasing artifacts in real-time multistatic millimeter-wave imaging systems.