A metamaterial-coupled wireless power transfer system based on cubic high-dielectric resonators

In this paper, a metamaterial-coupled, highly efficient, miniaturized, and long-range wireless power transfer (WPT) system based on a cubic high-dielectric resonator (CHDR) is explored. The proposed WPT system consists of two CHDR metamaterials separated by a distance and excited by two rectangular coils. Initially, this WPT system is analyzed by considering the cube dielectric permittivity, ε,. = 1000, and loss tangent, tanδ = 0.00001. From the Ansoft HFSS simulation, it is observed that the system operates in the hybrid resonance mode resonating as a horizontal magnetic dipole providing more than 90% power transfer efficiency at a distance of 0.1λ. In addition, parametric studies regarding the transmitter and receiver sizes, loss tangent, receiver misorientation, cube periodicity, etc., are carried out. One of the significant findings of this parametric study reveals that the suggested WPT system is less sensitive to the displacement of the receiver coil, and the WPT efficiency due to misorientation of the receiver can be increased by changing the CHDR cube rotation. Due to inaccessibility of the very high ε,. = 1000, 18 microwave ceramic samples of EXXELIA TEMEX E5080 (Oxide composition: Ba Sm Ti), which has a permittivity, ε,. = 78, permeability, μ,. = 1, and a loss tangent, tanδ = 0.0004, was made for experimental verification. These cubes are surrounded by Teflon to make the CHDR resonators. From simulations and measurements, it is found that the proposed system outperforms the most recent high-dielectric or copper-based WPT systems in terms of efficiency, range, size, and specific absorption rate

Design and SAR Analysis of AMC-Based Fabric Antenna for Body-Centric Communication

This study focused on the design and analysis of an artificial magnetic conductor (AMC)-based fabric antenna for body-centric communication. The antenna was made of felt and had a loss tangent of 0.044 and relative permittivity of 1.3. The proposed antenna was built to function in the frequency band centered at 2.45 GHz, widely used in wireless communication devices. The antenna’s performance was evaluated using the electromagnetic simulation software CST MWS. A 50 Ω SubMiniature version connector was used to excite the proposed antenna. A 2×2 AMC array was integrated into the antenna below it to improve its performance in terms of radiation efficiency, gain, and backward radiation reduction. The antenna and AMC array were fabricated on flexible fabric substrates. The total volume of the AMC-integrated antenna is 0.55λo×0.55λo×0.016λo . It was demonstrated that adding an AMC array enhanced the radiation properties of the antenna and significantly decreased its back lobes. The on- and off-body maximum gains of the AMC-integrated antenna are (≥ 4.11 dBi) and 5.23 dBi, respectively. Furthermore, employing the AMC array, a significant reduction in the specific absorption rate value, which is (≤ 0.43 W/kg) for human body tissue chest/back and (≤ 0.75 W/kg) for human body tissue arm, was obtained, ensuring safety for human use. The simulated and measured results were in agreement. The tested on- and off-body radiation efficiencies in the frequency band centered at 2.45 GHz is (>67%) and (>83%), respectively. The proposed antenna can potentially be used in various applications such as healthcare monitoring, wearable electronics, and Internet of Things (IoT) systems, where reliable and efficient communication is required in a body-centric environment

Wireless Power Transfer to a Pacemaker by Using Metamaterials and Yagi-Uda Antenna Concept

Wireless power transfer (WPT) to medical implants allows clinicians to avoid using bulky energy storage components. In this paper, we address WPT systems for a pacemaker (PM). A resonant inductive coupling method was employed in the WPT system by introducing a spiral transmitter (Tx) coil and a spiral receiver (Rx) coil. Here, we introduced the concept of the Yagi-Uda antenna by using metamaterials (MTMs) in order to increase WPT efficiency in the Medical Implanted Communication Service (MICS). Based on the simulation results in a realistic model of the human body, we were able to design a compact and efficient WPT system for PMs. Moreover, our simulation results showed that the Yagi-Uda antenna configuration can significantly increase WPT efficiency

A wideband circularly polarized conformal endoscopic antenna system for high-speed data transfer

In this paper, a conformal wideband circularly polarized (CP) antenna is presented for endoscopic capsule application over the 915-MHz Industrial, Scientific, and Medical (902-928 MHz) band. The thickness of the antenna is only 0.2 mm, which can be wrapped inside a capsule's inner wall. By cutting meandered slots on the patch, using open-end slots on the ground, and utilizing two long arms, the proposed antenna obtains a significant size reduction. In the conformal form, the antenna volume measures only 66.7 mm3. A single-layer homogeneous muscle phantom box is used for the initial design and optimization with parametric studies. The effect of the internal components inside a capsule is discussed in analyzing the antenna's performance and to realize a more practical scenario. In addition, a realistic human body model in a Remcom XFdtd simulation environment is considered to evaluate the antenna characteristics and CP purity, and to specify the specific absorption rate limit in different organs along the gastrointestinal tract. The performance of the proposed antenna is experimentally validated by using a minced pork muscle phantom and by using an American Society for Testing and Materials phantom immersed in a liquid solution. For measurements, a new technique applying a printed 3-D capsule is devised. From simulations and measurements, we found that the impedance bandwidth of the proposed antenna is more than 20% and with a maximum simulated axial ratio bandwidth of around 29.2% in homogeneous tissue. Finally, a wireless communication link at a data rate of 78 Mb/s is calculated by employing link-budget analysis

Application of a compact electromagnetic bandgap array in a phone case for suppression of mobile phone radiation exposure

In this paper, a mobile phone case incorporating electromagnetic bandgap (EBG) material is studied to intercept electromagnetic (EM) waves from the phone and reduce the specific absorption rate (SAR). A loop antenna for the personal communications service 1900-MHz band is considered. In addition, three different mobile phone cases associating EBG structures with optimized positions are used to improve SAR reduction. Furthermore, antenna performance with an EBG structure is investigated with a full-body EM simulation program, SEMCAD X, and an individual performance analysis of each EBG structure was carried out by using Ansoft HFSS. A human head phantom to replicate the specific anthropomorphic mannequin model was used for measurements. From simulation and measurement, it is found that placing an EBG structure in a phone case can improve antenna gain and reduce SAR. Moreover, a maximum gain increment of 19% and an SAR reduction of 24% were found. This paper reveals the future applications of EBG structures for SAR reduction in mobile phones

A Triple-Band Deep-Tissue Implantable Antenna Incorporating Biotelemetry and Unidirectional Wireless Power Transfer System

In this study, we introduce a triple-band flexible implantable antenna that is tuned by using a ground slot in three specific bands, namely Medical Implanted Communication Service (MICS: 402-405 MHz) for telemetry, the midfield band (lower gigahertz: 1.45-1.6 GHz) for Wireless Power Transfer (WPT), and the Industrial, Scientific and Medical band (ISM: 2.4-2.45 GHz) for power conservation. The telemetry performance of the proposed antenna was simulated and measured by using a porcine heart. To check the feasibility of WPT, a midfield transmitter antenna was introduced. In addition, to reduce the unwanted power leakage due to WPT, a Near Field Plate (NFP) was also used. Finally, power conservation can be realized by triggering the antennas sleep mode in the ISM band

A multiband antenna associating wireless monitoring and nonleaky wireless power transfer system for biomedical implants

This paper presents a multiband conformal antenna for implantable as well as ingestible devices. The proposed antenna has the following three bands: medical implanted communication service (MICS: 402-405 MHz), the midfield band (1.45-1.6 GHz), and the industrial, scientific, and medical band (ISM: 2.4-2.45 GHz) for telemetry or wireless monitoring, wireless power transfer (WPT), and power conservation, respectively. A T-shaped ground slot is used to tune the antenna, and this antenna is wrapped inside a printed 3-D capsule prototype to demonstrate its applicability in different biomedical devices. Initially, the performance of the proposed antenna was measured in an American Society for Testing and Materials phantom containing a porcine heart in the MICS band for an implantable case. Furthermore, to stretch the scope of the suggested antenna to ingestible devices, the antenna performance was simulated and measured using a minced pork muscle in the ISM band. A modified version of the midfield power transfer method was incorporated to replicate the idea of WPT within the implantable 3-D printed capsule. Moreover, a near-field plate (NFP) was employed to control the leakage of power from the WPT transmitter. From the simulation and measurements, we found that use of a ground slot in the implantable antenna can improve antenna performance and can also reduce the specific absorption rate. Furthermore, by including the NFP with the midfield WPT transmitter system, unidirectional wireless power can be obtained and WPT efficiency can be increased

Wireless Power Transfer and Biotelemetry in a Leadless Pacemaker

In this paper, we address the telemetry and wireless powering problems associated with the recently invented leadless pacemaker. To overcome the telemetry problem, we propose a conformal spiral type Implantable antenna at Medical Implanted Communication Service (MICS) band. In addition, we also apply the recently proposed midfield wireless power transfer (WPT) technique at 1.5 GHz to avoid the bulky energy storage component. We simulate and experimentally measure the performance of the implantable antenna by using porcine heart tissue. Our research shows that, the implantable antenna and wireless power transfer scheme can be implemented in a leadless pacemaker without any significant coupling between them

A New Medical Implant Lead for 1.5 T, 3 T, and 7 T MRI Systems

In the presence of an electrically conducting medical lead, Radio Frequency (RF) coils in Magnetic Resonance Imaging (MRI) systems may concentrate the RF energy and cause tissue heating near the lead. Here, we present a novel design for a medical lead to reduce this heating by introducing pins. A pin can be taught as an electrical short that connect the main lead to the surrounding tissues. Initially, detail analysis of our proposed design is carried out by using Ansoft HFSS. Then, peak 10 g Specific Absorption Rate (SAR) in heart tissue, an indicator of heating, was calculated and compared for both conventional design and our proposed design. Remcom XFdtd software was used to calculate the peak SAR distribution in a realistic model of the human body. The model contained a medical lead that was exposed to RF magnetic fields at 64 MHz (1.5 T), 128 MHz (3 T) and 300 MHz (7 T) using a model of an MR birdcage body coil. We demonstrate that our proposed design of adding pins to the medical lead can significantly reduce the heating from different MRI systems