Mehmet Bakir

Asymmetric Transmission of Linearly Polarized Waves and Dynamically Wave Rotation Using Chiral Metamaterial

The asymmetric transmission of the linearly polarized waves at normal incidence through the lossy anisotropic chiral structure is demonstrated. The proposed chiral metamaterial structure is composed of bi-layered discontinuous cross-wire-strips, and it is utilized in order to realize polarization rotation. Firstly, the theoretical relations between the incident polarization and the polarization rotation are derived using transmission matrices. Secondly, a strong and dynamically asymmetric transmission of linearly polarized electromagnetic wave through the chiral metamaterial has been demonstrated for microwave region, both by simulation and experimentally. The experiment results are in good agreement with the simulation ones. It can be seen from the results that the proposed chiral metamaterial structure can be used to design novel polarization control devices for several frequency regions.

Chiral Metamaterial Based Multifunctional Sensor Applications

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.

Biosensor applications of chiral metamaterials for marrowbone temperature sensing

In this paper, we have designed, simulated, and analyzed a microwave biosensor based on chiral metamaterials (MTMs) to detect pig biological tissues which are widely used as a trial for medical explorations and researches. There are various types of biosensor structures based on MTMs in the literature. However, only a limited number of study is conducted on biosensors based on chiral MTMs; therefore, our study is one of the pioneer works for this type of research. The proposed diamond-shaped resonator-based structures are numerically investigated and analyzed in detail in the microwave frequency regime. The results are in good agreement which lead us to conclude that our structure can be easily used as an effective instrument for biosensing applications in medical technologies.

Perfect metamaterial absorber-based energy harvesting and sensor applications in the industrial, scientific, and medical band

Abstract. 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.

Electromagnetic energy harvesting and density sensor application based on perfect metamaterial absorber

The proposed study presents an electromagnetic (EM) energy harvesting and density sensor application based on a perfect metamaterial absorber (MA) in microwave frequency regime. In order to verify the absorption behavior of the structure, its absorption behavior is experimentally tested along with the energy harvesting and sensing abilities. The absorption value is experimentally found 0.9 at the resonance frequency of 4.75 GHz. In order to harvest the EM energy, chips resistors are used. In addition, the suggested model is analyzed for its dependency on polarization angles. The results show that the perfect MA can be easily and efficiently used for EM energy harvesting applications. Moreover, as an additional feature of the model, we also realized a density sensor application. It can be seen that this structure can be used as a multi-functional device and configured for many other sensing applications.

Wideband metamaterial absorber based on CRRs with lumped elements for microwave energy harvesting

ABSTRACT 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.

Chiral metamaterial design using optimized pixelated inclusions with genetic algorithm

Abstract. Chiral metamaterials have been a research area for many researchers due to their polarization rotation properties on electromagnetic waves. However, most of the proposed chiral metamaterials are designed depending on experience or time-consuming inefficient simulations. A method is investigated for designing a chiral metamaterial with a strong and natural chirality admittance by optimizing a grid of metallic pixels through both sides of a dielectric sheet placed perpendicular to the incident wave by using a genetic algorithm (GA) technique based on finite element method solver. The effective medium parameters are obtained by using constitutive equations and S parameters. The proposed methodology is very efficient for designing a chiral metamaterial with the desired effective medium parameters. By using GA-based topology, it is proven that a chiral metamaterial can be designed and manufactured more easily and with a low cost.

Design of a dual band metamaterial absorber for Wi-Fi bands

The goal of this work is to design and fabrication of a dual band metamaterial based absorber for Wireless Fidelity (Wi-Fi) bands. Wi-Fi has two different operating frequencies such as 2.45 GHz and 5 GHz. A dual band absorber is proposed and the proposed structure consists of two layered unit cells, and different sized square split ring (SSR) resonators located on each layers. Copper is used for metal layer and resonator structure, FR-4 is used as substrate layer in the proposed structure. This designed dual band metamaterial absorber is used in the wireless frequency bands which has two center frequencies such as 2.45 GHz and 5 GHz. Finite Integration Technique (FIT) based simulation software used and according to FIT based simulation results, the absorption peak in the 2.45 GHz is about 90% and the another frequency 5 GHz has absorption peak near 99%. In addition, this proposed structure has a potential for energy harvesting applications in future works.

Fire detection behind a wall by using microwave techniques

In this work, detection of the fire location behind a wall by using microwave techniques is illustrated. According to Planck’s Law, Blackbody emits electromagnetic radiation in the microwave region of the electromagnetic spectrum. This emitted waves penetrates all materials except that metals. These radiated waves can be detected by using directional and high gain antennas. The proposed antenna consists of a simple microstrip patch antenna and a 2×2 microstrip patch antenna array. FIT based simulation results show that 2×2 array antenna can absorb emitted power from a fire source which is located behind a wall. This contribution can be inspirational for further works.

Electromagnetic energy harvesting by using tunable metamaterial absorbers

In this study, electromagnetic (EM) energy harvesting by using metamaterial absorber is numerically explained. Operation frequency is 2.40 GHz since it is the industrial scientific and medical (ISM) band. This band is especially chosen due to most of the customer electronic devices are working in this band. Split ring resonator that have two splits on it used in this study, chip resistors are placed on these splits for wireless energy transfer to the devices. 83.6% efficient electromagnetic energy harvesting is theoretically realized.