In this work, sensor abilities of a chiral metamaterial based on split ring resonators with double splits (SRDS) are demonstrated both theoretically and experimentally in X band range. This study is based on transmission measurements and simulations monitoring the resonance frequency changes with respect to the thickness of the sensing layer and permittivity values. Experimental and simulated results show that the resonance frequency of the chiral metamaterial based SRDS sensor is linearly related to the permittivity and the thickness of the sensor layer which creates a suitable approach for sensing environment and organic parameters. When the sensor layer filled with the related material, changes in the tissue temperature, sand humidity and calcium chloride density lead to resonance frequency changes. The physical mechanisms are explained by using both equivalent circuit model and the fundamental sensitivity theorem of chiral sensors. This is the first study investigating a sensing mechanism based on the chiral metamaterials in X band range.
4 December 2018 in International Journal of RF and Microwave Computer-Aided Engineering
We propose a microwave imaging structure with GSM, ISM, Wi-Fi, and WiMAX operating frequencies at 1.80, 2.45, and 5.80 GHz, respectively. The suggested structure is based on a microwave antenna-inspired absorber with cavities in resonator layers. Our study, which is validated using simulation and experimental techniques, deals with the absorption of the incident electromagnetic waves at 1.80, 2.45, and 5.80 GHz for creating the image when radio frequency microwave is employed. The above-mentioned three operating frequencies, by which electromagnetic waves are radiated from three different antennas, are read via digital oscilloscope and finally these voltages are converted to 256 gray-leveled pixel values of each cell. During the experimental testing, simulated and tested values complied with each other. Small differences occurred due to calibration and testing errors. The novelty of this study is having image capability with most commonly used frequency bands by absorbing microwave energy.
14 December 2017 in Journal of Microwave Power and Electromagnetic Energy
A novel metamaterial absorber structure is designed and characterized for microwave energy harvesting. The suggested structure is composed of two circular ring resonators with different dimensions. Due to harvesting application of the proposed structure, the main operation frequency of the suggested structure lies in WIMAX and satellite communication frequency bands and surrounds our environment. The optimum dimensions of the suggested structure are obtained through parametric study by genetic algorithm in order to realize wideband absorption and harvesting response. Simulation results show that the metamaterial-harvester-based resistive loads are useful to absorb and convert microwave energy for the operation frequency. The simulated harvested power across the resistors has been found greater than 0.4 W, which corresponds to 80% efficiency between 7.8 and 14 GHz. In addition, polarization dependence and angular stability of the proposed harvester are investigated at operation frequency to support the simulation of an experimental study for S-parameter measurement. Therefore, simulation and experimental study results show that the proposed design with good absorption and harvesting characteristics can be operated in WIMAX and satellite communication frequency bands.
An electromagnetic (EM) energy harvesting application based on metamaterials is introduced. This application is operating at the the industrial, scientific, and medical band (2.40 GHz), which is especially chosen because of its wide usage area. A square ring resonator (SRR) which has two gaps and two resistors across the gaps on it is used. Chip resistors are used to deliver the power to any active component that requires power. Transmission and reflection characteristics of the metamaterial absorber for energy harvesting application are theoretically investigated and 83.6% efficient energy harvesting application is realized. To prove that this study can be used for different sensor applications other than harvesting, a temperature sensor configuration is developed that can be applied to other sensing applications.