Design of high-resolution near-field focusing metasurface lens

Abstract

A high-resolution near-field focusing metasurface lens (MSL) was proposed to meet the high-resolution and miniaturization requirements of focusing devices in the Ka-band passive millimeter wave (PMMW) imaging system. Based on coaxial ring structure with polarization insensitivity, the design of a single refraction surface phase gradient MSL capable of focusing on plane waves is completed. Furthermore, the near-field focusing is realized by the method of phase superposition. The overall size of the lens s is 80 × 80 mm2, composed of 25 × 25 unit with the thickness of only 0.24λ. The feed source used a tapered slot antenna based on substrate integrated waveguide. The simulation results indicate a good spatial resolution of the presented lens, which can focus the electromagnetic wave radiated from the feed antenna at 70 mm with the focal spot size of 9 mm. The lens can effectively reduce the system volume and achieve high resolution imaging when utilized in PMMW imaging system.