Quality Improvement of Millimeter-Wave Imaging Systems Using Optimized Dual Polarized Arrays

In this article, we propose a software-hardware system to improve the quality of image recovery in millimeter-wave (MMW) imaging systems, which aims to benefit from copolarization and cross-polarization scatterings from the target. The proposed dual-polarized antenna array structures consist of two orthogonal subarrays with the same phase center, where each subarray is comprised of 2\times 1 or 4\times 1 rectangular edge fed patches and the optimized ground defects. These compact structures, which support radiation of two orthogonal linear polarizations, are designed on a single-layer board using crossover technique. The dual-polarized scattering from the target is captured by the orthogonal subarrays. Furthermore, we introduce a method to combine data obtained from measured dual (co- and cross-) polarized fields to improve the recovery of edge information and increase image quality. The proposed single-layer designs have been fabricated and measured, which exhibits high port isolation and high polarization purity. The cross-polarization level is at least 22 and 25 dB lower than the copolarization pattern for 2\times 1 and 4\times 1 arrays, respectively. The measured 10 dB impedance bandwidth of the 2 \times 1 and 4\times 1 subarrays ranges from 27 to 29.3 GHz and from 27 to 29.5 GHz, respectively. Moreover, the radiation gains of the 2 \times 1 and 4\times 1 subarrays are 9.7 and 12 dBi, respectively. The simulated and measured imaging results show that the cross-polarized data preserve the edge information. Moreover, by using the proposed data combination technique, the quality of the recovered image is improved.