Efficient Metasurface-based Absorber for Microwave Applications

Abstract

Metasurfaces are the artificial periodic surfaces which provide desirable properties not due to to their materials but due to their shapes. The metasurface can be technically engineered to obtain different device based applications such as polarization conversion, beam splitter, sensors, resonators, filters, power dividers, antennas and absorbers. Due to its major role in applications, absorbers has always been of central interest to modern engineering and scientific society. Electromagnetic wave absorbers are used in anechoic chamber, electromagnetic compatibility (EMC) applications, concealment, stealth technology and reduction of automotive false imaging. Although the absorption can be easily achieved by passing waves through lossy materials but these absorbers are bulky in size. In order to achieve electromagnetic wave absorption using compact structure, the focus of researchers have shifted towards metasurfaces. In this regard, metasurface based absorbers have been reported in literature at microwave frequency range but they are either single band, narrow band, polarization sensitive or not angular stable. In this thesis, a cyclic four (C4) symmetrical metasurface is designed to achieve electromagnetic waves absorption in microwave frequency regime. The proposed metasurface based absorber is designed to achieve multi characteristics such as multiband, broadband, polarization insensitive, and angular stability. The structure provides absorption at six resonant frequency bands. Comparatively broad absorption bandwidth (930 MHz) achieved at last frequency band using single layer structure without resistive elements. The unique physical structure, sub-wavelength size and small thickness of substrate make the response of metasurface same for both transverse electric (TE) and transverse magnetic (TM) polarized waves and insensitive to incident angle for lower two frequency bands. The multi characteristics and compact size make the metasurface based absorber, a potential candidate for S, C, X, Ku and K bands applications This thesis also includes surface currents distribution and angular stability analysis of the proposed absorber to understand its physical behavior. The proposed design is validated by experimental measurements.