Design of resonator based multi-band absorber and sensor applications

In this thesis, resonator-based multi-band absorber design and sensor applications have been investigated. The proposed designs consist of a resonator at the top, a dielectric substrate in the middle and a ground plane at the bottom. In the designs, asymmetric X-shaped resonator and metamaterial elements such as split ring resonator (SRR), electric LC resonator (ELC) are used as frequency determining elements. A relatively miniaturized tri-band absorber covering WiMAX and WLAN bands has been designed in the simulation environment using three circular and concentric SRR. The ELC resonator, which is a metamaterial element, is placed on a 3D printed dielectric substrate to design absorber sensor. There is a cavity in the 3D-printed substrate to integrate the samples into the sensor. Thanks to the cavity, both solid and liquid analyses can be performed. It is a monolithic and simple structure, so it is effortless to manufacture and implement. To validate this design, the absorber sensor is fabricated, measured, and analytically modeled. A compact absorber has been designed using an X-shaped resonator that exhibits single or dual-band behavior depending on whether the arm lengths are symmetric or asymmetric. The sensor performance of this structure consisting of a resonator and a substrate has been investigated in simulation and measurement. In this context, the asymmetric X-shaped absorber is found to be more sensitive when compared with two SRR-based absorber sensors with different absorption frequencies. Then, two asymmetric X-shaped resonators with varying lengths of arm are placed on denim fabric used as a substrate to obtain a four-band absorber. This quad-band design, whose numerical and experimental results are in perfect agreement, is a good candidate for wearable applications. Lastly, in a simulation environment, frequency tunable absorbers are designed by integrating PIN and varactor diodes into the asymmetric X-shaped resonator. Thanks to the proposed designs, the absorption frequencies do not remain fixed after fabrication like conventional absorbers, and the applications of the absorber are expanded.