Design and realization of a broad band antenna loaded with a metamaterial-inspired lens for subsurface microwave imaging applications

Yeşilyurt, Ömer
Ultra-wideband antennas are critical sensors for microwave imaging. In this work, radiation performance of an antipodal Vivaldi antenna is enhanced by using a broadband metasurface lens structure in 1-6 GHz bandwidth. Radiation pattern for the lens integrated antenna is more directive due to electromagnetic properties of the metasurface lens. In order to create such a lens, electrically responsive metamaterial unit cells with high effective permittivity values are designed. As we want to obtain a broadband antenna performance, metamaterial unit cell dimensions are adjusted to avoid the resonance regions of the metasurface over the desired operation bandwidth of the antenna. Overall lens structure is etched over the same substrate containing the antipodal Vivaldi antenna resulting in a compact design. Far-field radiation patterns indicate that more directive beam is radiated from the antenna with metasurface lens. Measurement and simulation results show that directivity is increased considerably without affecting the efficiency characteristics of the antenna. Microwave image of a shallowly buried conducting object is constructed by using with metasurface integrated antenna and also by using the conventional antipodal Vivaldi antenna as sensors. Two-dimensional microwave images are constructed by using the total energy values of the time signals measured at each spatial sampling point. Due to its more directive radiation pattern, the images obtained by the antenna with metasurface lens are observed to have better resolution.