Near field microwave subsurface imaging using metasurface loaded planar antenna and synthetic aperture radar (SAR) technique

Abstract

A novel near field subsurface microwave imaging scheme is proposed by using a high gain planar metasurface (MS) loaded slot antenna integrated with the synthetic aperture radar (SAR) algorithm. The antenna structure here comprises a slot antenna integrated with the proposed MS designed using the epsilon very large (EVL) unit cell. The proposed MS-based antenna structure has a very low profile of 0.033λ, with a measured peak gain of 5.5 dB at 6.47 GHz. After adding two more additional MS layers, the peak gain of the resultant antenna is 12.1 dB. The broadside gain and efficiency are significantly enhanced with the incorporation of the EVL MS. Afterward, the antenna structure, along with the vector network analyzer and the 2-D automated scanner is employed for the near field imaging of test media by recording the scattering data along the target area. A spatial subwavelength resolution with a typical value of about 0.43λ is obtained at 1λ standoff distance after applying the single frequency SAR algorithm to the measured raw scattering data. The overall applicability of the proposed low-profile MS loaded antenna integrated with the SAR algorithm is demonstrated for the near field subsurface microwave imaging of various metallic and dielectric targets with subwavelength spatial resolution in free space and lossy media.