Numerical investigation on graphene based mantle cloaking of a PEC cylinder

A specific coating for the achievement of the mantle cloaking of a metallic cylinder in the Terahertz frequencies is investigated. The coat is realized starting from a dielectric layer covering the cylinder, over which a certain number of modulated strips of graphene are laid. Properly set the values of the available parameters (chemical potential of graphene μc, dielectric constant, dielectric thickness h, number of modulated strips n and variation of width of each strip w(z)), a combination of the values that allows to reach the cloaking of the object is obtained. In order to quantify the cloaking at the desired frequency f0, the Maximum Radar Cross Section is computed and compared to the various structures

Harmonic analysis and reduction of the scattered field from electrically large cloaked metallic cylinders

In this paper, an analysis of the spectral composition of the scattered field from coated metallic cylinders is performed, focusing particularly on the cloaking of electrically large structures. An expression of the scattering coefficients is derived, considering both a dielectric and a metasurface coating. Modeling the metasurface as a surface impedance boundary condition, the surface impedance, which annuls one harmonic of the scattered field, is formulated in a closed and compact form. Moreover, in the case of cylinders with radius comparable with the wavelength of interest, it is demonstrated that a reduction of the scattering is possible by using a homogeneous metasurface coating, which presents a positive surface reactance. In particular, a reduction of the scattering width of 4 dB is achieved for a cylinder radius of a = 0.917λ0

Multidisciplinary investigations on the use of TiNb alloy orthopedic device equipped with low profile antenna as smart sensor

In this paper, a new complex medical device is proposed using TiNb based metallic alloy, acting also as a ground plane for a low profile printed antenna sited on a Polydimethylsiloxane (PDMS) substrate. The first step of the research is oriented on the experimental study of the properties of TiNb based alloy and on the development of the orthopedic device. The second step is focalized on the electromagnetic characterization of the implanted printed antennas. The resulting smart orthopedic device incorporating the antenna and when embedded in a body environment is numerically analyzed from communication point of view. In particular, the radiation characteristics, necessary for the calculation of the link budget when the device is used for communication with the external to the body receiver is considered. Such scenario finds its applications in monitoring some vital human functions for example in post chirurgical rehabilitation or other long-term surveys

An ideal dielectric coat to avoid prosthesis RF-artefacts in Magnetic Resonance Imaging

The number of people submitted to total hip or knee arthroplasty increased in the last years and it is likely to grow further. Hence, the importance of a proper investigation tool that allows to determine and recognize the potential presence of perioperative and/or postoperative diseases becomes clear. Although the Magnetic Resonance Imaging (MRI) technique demonstrated several advantages over the other common tomography tools, it suffers from the arise of image artefacts if it is performed in presence of metallic prostheses. In particular, the so-called RF-artefacts are caused by the inhomogeneity in the radiofrequency magnetic field of MRI, due to the electric currents induced on the metal surface by the field itself. In this work, a near-zero permittivity dielectric coat is simulated to reduce those currents and, therefore, the RF-artefacts onset in the final image. Numerical results confirm that the dielectric coat strongly reduces the magnetic field inhomogeneity, suggesting a possible solution to a well-known problem in the MRI field

Multi-band Implantable Microstrip Antenna on Large Ground Plane and TiO2 Substrate

Biomedical implanted devices are typically used for interacting with organs and/or for investigating various physiological signals. Hence, enhanced performance devices for clinical uses have got the attention of researchers. In this study, a multi-band implanted microstrip antenna suitable for transmitting/receiving biomedical signals in the Industrial, Scientific and Medical (ISM) frequency bands is presented. The antenna is built on a bio-compatible substrate, as titanium dioxide (TiO2) with relative permittivity of 95. The ground plane is thought to be a bio-metallic implant located within a bone. The proposed antenna is compact in size, 14 × 18 × 1.6 mm3, and works in both 2.45 GHz and 5.8 GHz centered frequency bands. It is designed and optimized considering the actual biological tissues as bone, muscle, fat, and skin surroundings. The simulation results referring to a planar stratification prove that the multiband single microstrip antenna is working properly within the human body and it can be used for medical communication services

Optimal Huygens' Metasurface for Wireless Power Transfer Efficiency Improvement

In this paper, we investigate the electromagnetic response of a Huygens' metasurface (HMS) embedded between the transmitter and receiver coils of a near field wireless power transfer (WPT) system and their interactions for the feasibility of increasing efficiency. To analyze the proposed configuration, we use the point-dipole approximation to describe the electromagnetic fields and boundary conditions governing HMS to calculate the mutual inductance between the coils and to obtain closed-form analytical expressions. The proposed theory shows that by optimally designing the HMS inclusions, the amplitude of the mutual inductance between the transmitter and receiver coils in the near-field WPT can be increased, resulting in improved efficiency. Finally, by drawing on the proposed theory, we design a thin layer and finite-size HMS consisting of 64 elements. The bianisotropic Omega-type particle is used to design the HMS to improve the efficiency of the sample WPT system at the frequency of 100 MHz. The results of the full-wave simulation show that the power transfer efficiency in the free space increases from 25% to 42% in the presence of the proposed HMS

MIMO Antenna Optimization: From Configuring Structure to Sizing with the aid of Neural Network

In the last decades, multiple input, multiple output (MIMO) antenna designs play important role and this trend will continue in next-generation mobile technologies. Designing high-performance MIMOs is significant since these types of antennas include multiple radiating elements. For these complex configurations, intelligent-based optimization methods can tackle the problem of designing. This paper devotes to designing and optimizing the configuration and design parameters of a MIMO antenna, respectively. Firstly bottom-up optimization (BUO) approach is executed successfully for building the general topology of the MIMO antenna and afterwards, artificial neural network (ANN) is utilized for obtaining the design parameters with the optimal values. The proposed approach results in generating the optimal topology with size values in a reduced effort by designers. The presented approach is applied to designing a MIMO antenna operating from 13.7 GHz to 29 GHz

All-dielectric nanoantenna for efficient reflectors irradiation

In this paper, we propose a new kind of nanoantenna for effective illumination of parabolic surfaces, constituting of a silicon cylinder acting as a reflector and dipole source as an emitter. Tailored parameters of the nanoantenna ensure specific radiation pattern with broad main lobe and strongly suppressed side lobes that in the E-plane of the dipole is quite similar to the ideal “П” configuration, necessary for an as uniform as possible illumination of parabolic surfaces. This above radiation pattern is mostly due to the properly designed dielectric inclusion in the reflector that, therefore, is free of any losses. Consequently, we study how varying the antenna parameters affects the radiation pattern.Results of our numerical simulations are compared with already existing ones and highlight the principal features that provide the desired effect. Furthermore, due to the simple geometry of the inclusions, the considered nanoantenna, required in application such as nanoreflector antennas and/or nanophotonic devices, exhibits advantages in manufacturing processes with respect to already proposed solutions

Optimization for wideband linear array antenna through bottom-up method

This paper presents an automated design methodology for electromagnetic- based (EM-based) optimization of an array antenna by applying bottom-up approach. Firstly, one single antenna is optimized then bottom-up optimization (BUO) method has been implemented by increasing the number of single antennas, sequentially. The proposed method leads to automatically find an optimal array by setting the distance between single antennas. The optimization method is performed in an automated environment with the help of an electronic design automation (EDA) tool and a numerical analyzer. The results of the final design have been compared by means of two EDA tools such as ADS and HFSS. The optimized array antenna works in the frequency band from 12.9 GHz to 14.3 GHz. It offers a linear gain performance higher than 7.5 dB. The simulations in both ADS and HFSS tools illustrate a good match in S-parameter and gain simulation output results