Tunable Metamaterials

Abstract

Metamaterials (MTM) are composite materials that provide some unique characteristics which are not available by nature. But there is one major drawback or limitation of MTM which is its fixed and narrow working frequency region. To overcome this limitation, there are few techniques, presented in this thesis, to vary the working frequency band of MTM. As MTM are artificial materials, so there are various resonators available in literature, presented for MTM. In this thesis, three resonators, split ring resonator (SRR), S-shaped resonator (SSR) and single side paired S-ring resonator (SSPSRR) have been chosen from literature and different techniques to shift their resonant frequencies are presented. For SRR, a tunable case i.e., inner ring shorted split ring resonator (IRS-SRR) is pre- sented in this thesis. The analytical expression of the effective permeability of IRS-SRR is calculated and for the verification of the analytical work, the experimental results are also included in this thesis. The analytical expression for the effective permeability of SSR is also presented in this thesis. Two tunable or modified cases of SSR, i.e., bottom metallic strips shorted S-shaped resonator (BSSR) and top-bottom metallic strips shorted S-shaped resonator (TBSSR) are presented in this thesis. The analytical expressions of the effective permeabilities of BSSR and TBSSR are also calculated. For verification of the analytical work of SSR, BSSR and TBSSR, experimental results are included in this thesis. Similar to SSR, the analytical expression of the effective permeability of SSPSRR is presented in this thesis and the experimental results are also included to verify the analytical work. Two tunable cases of SSPSRR, i.e., bottom metallic strips shorted single side paired S- ring resonator (B-SSPSRR) and top-bottom metallic strips shorted single side paired S-ring resonator (TB-SSPSRR), are also presented in this thesis along with experimental results. Other than the tunable cases of various resonators, rotation of resonators is presented in this thesis as a technique to vary the working frequency of MTM. This technique has been applied on SSR, SSPSRR and their respective tunable cases in this thesis and the vexperimental results are presented for justification of this technique. There are number of devices (made using MTM), are available in literature. All these devices can be upgraded to work as tunable devices using the techniques presented in this thesis.