Development of miniaturized metamaterial absorbers for electromagnetic radiation absorption in the microwave and near infrared regions

Abstract

The exotic characteristics of electromagnetic metamaterial absorber made it the focal point of wireless electromagnetic communication system. Many metamaterial absorbers already been proposed but the limitations are that most of them are bulky in size, poor performance, using multi-layers, and above all no scientific explanations were described regarding the structural parameters related to the metamaterial absorber (MMA) properties. The main aim of the thesis is to design, characterization and giving vivid scientific explanations of electromagnetic wave absorption mechanism for perfect MMA in the microwave regime and near infrared (NIR) of solar spectrum. It is also shown to relate the structural parameters with the resonance frequencies by designing some new metamaterial based absorbers. Hereafter, designing a miniaturized single layered perfect metamaterial absorber in the microwave and near infrared frequency band have become new research work for scientific community. Three new compact design structures were developed and analysed in this research to absorb the electromagnetic wave in the microwave regime and these three designs were implemented to absorb solar radiation in the near infrared (NIR) regime by using rescaling method. The proposed MMAs were numerically analysed by using Finite Integration Technique (FIT) based high frequency electromagnetic simulator (CST) microwave studio. The two important methods, Nicolson-Ross-Weir (NRW) and Fresnel method were used to characterize the MMAs extracting the material properties such as permittivity, permeability and refractive index. After that the electromagnetic behaviour of microwave absorbers were authenticated by LC tank circuit and experimentally measured by a vector network analyser. The first design was comprised with four symmetric swastika shaped with a circular split ring that yielded three resonance peaks at 3.03, 5.83 and 7.23 GHz with the absorbance of 99.84%, 99.03% and 98.26%, respectively. It covered S-, and C-band of satellite applications. The second design consisted of two orbits like circular rings with a metal disc on the orbit and circular metal disc in the centre of two orbits which yielded three absorption peaks at 3.02, 5.71 and 8.36 GHz with the absorbance of 99.86%, 97.58% and 97.46%, respectively. The third one was a cart wheel shaped MMA that yielded quadruple absorbance peaks at 2.88, 5.42, 7.62 and 10.24 GHz with the absorbance 99.73%, 93.57%, 99.68% and 99.78%, respectively. In addition, these three perfect MMAs were rescaled to design nano MMA structures to absorb solar energy. Maximum rates of absorbance numerically analysed by the CST microwave studio were 97.32%, 97.62% and 99.74% at 378, 234.80 and 199.30 THz for the swastika shaped, solar system shaped and cart-wheel shaped, respectively. These analyses propose the practical applications of satellite communications, radar cross-section, stealth and coating technologies, defense and security purposes for next generation EM communication devices.