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For wireless power transfer (WPT), an implantable cubic rectenna multi-input-multi-output (MIMO) system (CRMS), operating in dual industrial, scientific, and medical (ISM) frequency bands of 2.45 and 5.8 GHz, is presented as a receiver ( $R_{x}$ ). CRMS is evolved to the proposed biocompatible full-package cubic rectenna (FPCR) by including the power and data management circuit modules. The dual frequency bands differentiated by orthogonal circular polarization (CP) in a spatial quadrature would serve as propagation channels for power, data, and control signals. Four dual-branch rectifiers are designed using both distributed and lumped elements on the backside of individual antenna elements. To demonstrate the feasibility of the proposed work as an integrated system for WPT, the structures are fabricated individually, where the transmitter ( $T_{x}$ ), which is an external antenna, and rectifiers are tested in free space and FPCR in a custom-made canonical phantom. After validation of individual measurements, power delivery from the $T_{x}$ to the FPCR is conducted experimentally to measure the integrated system’s radiofrequency (RF)-dc total conversion efficiency (TCE). The FPCR is designed to receive low RF power ( $P_{\mathrm {RF}}$ ) of 0 dBm, where a single cubic rectenna element (CRE) provides dc power ( $P_{\mathrm {DC}}$ ) of 0.26 and 0.33 mW at 2.45 and 5.8 GHz, respectively. Thereafter, the interconnection of CREs in a series/parallel configuration improved $P_{\mathrm {DC}}$ to $0.5\mathbf {/}1.39$ and $0.51\mathbf {/}1.64$ mW, respectively. Additionally, human safety is considered by evaluating a maximum permissible exposure (MPE) limit and specific absorption rate (SAR) distribution in a canonical tissue model when both $T_{x}$ and FPCR are excited with 1 W power.

In the present paper (1-x)Pb (Zr1-yTiy)O3 – xPb (Mn1/3Sb2/3)O3 – z at%E system, with E = Pr3+, Nd5+ and Gd3+ where x = 0.12; y = 0.48; z = 0 and 0.02 ceramic synthesized by solid state reaction technique is analysed. The investigation aims studying of the effect of dopants on the dielectric and piezoelectric properties of such piezoelectric ceramic. The prepared powders have been uniaxially pressed into discs with diameter of 10 – 12 mm and thickness of 1.2 mm. Sintering has been carried out in air atmosphere at temperatures of 1150°C and 1200°C, respectively, for 2 hours each, followed by a controlled cooling at a rate of 200°C /h. The piezoelectric properties have been investigated after a suitable preparation, including polishing, metallization. The structure of the samples has been determined by X-ray diffractometry (XRD), while the morphology and grains size have been investigated by the scanning electron microscopy (SEM). The piezoelectric properties have been studied by the resonance - antiresonance method. XRD analysis reveals a perovskite tetragonal structure and, as expected for ceramic materials, SEM analysis indicates that the average grain size increases as sintering temperature increases. The dielectric and piezoelectric properties have been determined measuring the ceramic discs, and properties, as dielectric permittivity (εr), dielectric loss (tg δ), and the electromechanical coupling factor (kp) have been obtained. The acquired results indicate a significant effect of the dopants on the dielectric and piezoelectric properties of such materials.

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 = 0.917{\lambda _0} $a=0.917λ_0.

The objective of this paper is to analyze a near-field electromagnetic cloaking to reduce the radiofrequency (RF) magnetic field inhomogeneities (responsible for the RF-artefacts onset) in magnetic resonance imaging (MRI) in the presence of an elongated metallic hardware. A lumped circuit is considered to explain the role that a dielectric coat has on hiding a metallic cylinder to the RF antenna. The theoretical assumptions are proved by means of full-wave simulations that are also applied to a realistic hip prosthesis considering a frequency equal to 64 and 128 MHz. The numerical results confirm the theoretical assumptions. Both the theoretical analysis and the numerical simulations highlight the different role that the coat thickness and electric permittivity have in the definition of a proper dielectric coat. A particular cloaking approach leads to a dielectric coat whose constitutive electrical parameters may be simple enough to fit the considered application reducing the interaction between an elongated prosthesis and the RF antenna. Furthermore, results obtained at 64 MHz suggest the possibility to employ an existing biocompatible material to achieve the envisaged purposes.

The problem of suppressing the scattering from conductive objects is addressed in terms of harmonic contrast reduction. A unique compact closed-form solution for a surface impedance Z_s(m,  kr) is found in a straightforward manner and without any approximation as a function of the harmonic index m (scattering mode to suppress) and of the frequency regime kr (product of wavenumber k and radius r of the cloaked system) at any frequency regime. In the quasi-static limit, mantle cloaking is obtained as a particular case for kr≪1 and m=0. In addition, beyond the quasi-static regime, impedance coatings for a selected dominant harmonic wave can be designed with proper dispersive behavior, resulting in improved reduction levels and harmonic filtering capability.

Conformal metasurfaces are even more diffused in different fields from optics to electromagnetics. Advanced applications, as making object invisible to incident fields also known as cloaking, require high precision realizations, since the resonant answer of the system is very sensitive to geometry details. Practical realizations are provocative, since material characteristics and mechanical restrictions should also be considered. Multi- and inter-disciplinary interactions are mandatory to overcome such technological challenges. Due to its excellent esthetic characteristics, good physical and mechanical properties, Aluminium is widely used for deposition on different substrates: physical and chemical vapor depositions are very suitable for micro-metallization process and for the realization of multilayered structures. This paper presents some results about the behavior of a cylindrical-shape system realized by Al films deposition on flexible, polymeric organosilicon substrate.

We introduce a metamaterial based parallel-plate waveguide, devised in microstrip technology that features two electromagnetic band-gaps. Since one of the band-gaps extends from zero frequency, the structure can be used as a band-pass filter. We perform a parametric study in view of facilitating design and optimisation.

This work numerically explores the relations between the positions and the widths of the frequency bandgaps that occur in some shielded high impedance surfaces and the geometrical dimensions of the structures. The reported parameterized results are useful for design issues and for circuit models conception and validation.

This two‐part article presents a review of different techniques of mutual coupling (MC) reduction. MC reduction is a primary concern while designing a compact multiple‐input‐multiple‐output (MIMO) antenna where the separation between the antennas is less than λ0/2, that is, half of the free‐space wavelength. The negative permittivity and permeability of artificially created materials/structures (Metamaterials) significantly help reduce MC among narrow‐band compact MIMO antenna design elements. In this part two of the review paper, we will discuss techniques: Metamaterials; Split‐Ring‐Resonator; Complementary‐Split‐Ring‐Resonator; Frequency Selective Surface, Metasurface, Electromagnetic Band Gap structure, Decoupling and Matching network, Neutralization line, Cloaking Structures, Shorting vias and pins and few more. Mutual coupling (MC) reduction among antenna elements is a significant challenge while designing a compact MIMO antenna designThe negative permittivity and permeability property of Metamaterials helps in suppressing the ground wave propagationSome more MC reduction techniques have been discussed thoroughly in this article, like Electromagnetic Band Gap (EBG) structure, Decoupling and Matching network, and Neutralization line Mutual coupling (MC) reduction among antenna elements is a significant challenge while designing a compact MIMO antenna design The negative permittivity and permeability property of Metamaterials helps in suppressing the ground wave propagation Some more MC reduction techniques have been discussed thoroughly in this article, like Electromagnetic Band Gap (EBG) structure, Decoupling and Matching network, and Neutralization line

This two‐part article presents a review of different techniques of mutual coupling (MC) reduction. MC is a major issue when an array of antennas is densely packed. When the separation between the antennas is <λ0/2, i.e., half of the free‐space wavelength, the antenna parameters suffer from the surface wave, and the space wave coupling effect between the antenna elements. To reduce the MC influence, several techniques have been discussed in the scientific literature. This part of the review paper will discuss strategies: antenna placement and orientation approach, Defected Ground Structures (DGSs), slots/slits‐etching approach, protruding ground stub structures, and parasitic elements/structures. This article concludes with feasibility, applications, and comparison of the techniques mentioned above. Simultaneously, the applications and possibilities of the remaining methods are discussed in part two of the article. A comprehensive two‐part review article with more than 330 references is proposed. Multiple‐Input‐Multiple‐Output (MIMO) patch antenna is required for high data rate transmission without additional bandwidth requirementMutual coupling reduction among antenna elements is a significant challenge while designing a compact antenna array systemDefected Ground Structures and Parasitics elements/structures for mutual coupling reduction have been discussed thoroughly in this article Multiple‐Input‐Multiple‐Output (MIMO) patch antenna is required for high data rate transmission without additional bandwidth requirement Mutual coupling reduction among antenna elements is a significant challenge while designing a compact antenna array system Defected Ground Structures and Parasitics elements/structures for mutual coupling reduction have been discussed thoroughly in this article