Planar monopole antennas with reflection plane for human body centric communication

Wireless Body Area Network (WBAN) is an emerging technology that requires an antenna to be placed on human body for a wide range of applications such as healthcare, entertainment, surveillance, emergency and military. The reflection coefficient magnitude of the antenna in closeness to the human body is degraded and shifted. Essentially, efficiency and gain reduction are the main disadvantages of the antenna performances due to the body effect. In this research, methods of improving efficiency, gain, Specific Absorption Rate (SAR) and stabilizing reflection coefficient magnitude have been proposed. In this work, the design, simulation and fabrication of two monopole antennas with P-shaped and circular-shaped are presented. The proposed P-shaped monopole antenna is designed to operate from 3.1 to 5.1 GHz while the proposed circular-shaped monopole antenna operates at 3.1-5.1 GHz and 6.5-8 GHz. The simulation of the proposed antennas in free space and close proximity of body surface has been carried out using Computer Simulation Technology (CST) Microwave Studio. It has been found that when the P-shaped and circular elements are introduced to the ground plane of the antennas, the reflection coefficient magnitudes with the presence of body for both antennas remain the same as in free space. Moreover, the efficiency and gain of the antennas have been improved by attaching the glass substrate to the ground plane. P-shaped antenna with the glass substrate has demonstrated about 34.6%, 35% and 39.2% improvement of the antenna efficiency at 3.3, 4.45 and 5 GHz, respectively, when placed directly on the human head. For the human chest placement, the antenna demonstrates 30.7%, 33.4% and 36%, and the gain of 3.4, 2.8 and 4 dBi of antenna efficiency and gain improvement at 3.3, 4.45 and 5 GHz, respectively. Similarly, for circular-shaped monopole antenna the improvement of the antenna efficiency obtained for human head are 39.8% and 37.23% at 3.3 and 7.5 GHz, respectively, and for the chest are 36.5% and 32.8% at 3.3 and 7.5 GHz, accordingly. The antenna demonstrates 2.9 and 2.54 dBi improvement of the gain at 3.3 and 7.5 GHz, respectively. These improvements are compared with the antenna without the glass substrate. This study concludes that the glass substrate has improved the gain, efficiency and SAR when placed near human body compared to other antennas and the S11 remains stable when some additional elements are introduced to the ground plane. It was observed that there is good agreement between the simulation and measurement results, thereby showing that the antennas have potential to be deployed for WBAN application

Active textile multi-antenna systems for energy-efficient body-centric communication

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Realistic performance measurement for body-centric spatial modulation links

Spatial Modulation is a new transmission mode which increases spectral efficiency by employing information-driven transmit antenna selection. This performance is realized at a reduced hardware complexity and cost because only a single radio-frequency transmit chain is necessary. A measurement campaign is performed to assess the characteristics of spatial modulation over a body-centric communication channel, transmitting from a walking person with textile antennas integrated into the front and back sections of a garment, towards a base-station in realistic conditions. In the transmitted frames, additional spatial multiplexing as well as space-time coded data blocks are included. The off-body communication link is analyzed for line-of-sight as well as non line-of-sight radio wave propagation, comparing the characteristics of the different transmission modes under equal propagation conditions and for an equal channel capacity of 2 bit/s/Hz

Substrate integrated waveguide textile antennas as energy harvesting platforms

Textile multi-antenna systems are key components of smart fabric and interactive textile (SFIT) systems, as they establish reliable and energy-efficient wireless body-centric communication links. In this work, we investigate how their functionality can further be extended by exploiting their surface as an energy harvesting and power management platform. We provide guidelines for selecting an appropriate antenna topology and describe a suitable integration procedure. We demonstrate this approach by integrating two flexible solar cells, a micro-energy cell and a flexible power management system onto a well-chosen wearable substrate integrated waveguide cavity-backed textile slot antenna, without affecting its performance, to enable energy harvesting from solar and artificial light. In addition, the compact and highly-integrated harvesting module provides a terminal for connecting a thermoelectric generator, enabling thermal body energy harvesting. Measurements in a realistic indoor environment have demonstrated that this hybrid energy harvesting approach leverages a more continuous flow of scavenged energy, enabling energy scavenging in most of the indoor and outdoor scenarios

Fabrication of Human Body Phantom for Body Centric Communication Systems at 2.4 GHz

This research is intending to investigate the human skin phantom’s dielectric constant. The phantom will be used to test the electromagnetic compatibility later on since it can be harmful if it is directly tested on real human body. The human body phantom is made to have similar property as a skin tissue, at the operating frequency of 2.4 GHz. A methodology of the process is discussed. The phantom is fabricated, tested and measured. A fabricated phantom with the desired permittivity of εr and conductivity of σ values; are controlled by the amount of polyethylene powder and sodium chloride. The information on dielectric constant of the phantom based on measured values of εr and σ will be determined. The factors in making a good phantom is discussed. A good level of agreement is observed between simulation and measurement results

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

Cylindrically-bent rectangular patch antennas: novel modeling techniques for resonance frequency variation and uncertainty

Wearable textile antennas are basic components in body-centric communication systems. Flexible wearable patch antennas, when integrated into a body-worn garment are subjected to bending, causing variation in the resonance frequency when compared to the flat-antenna. Bending conditions vary statistically among different human subjects. Therefore, it is very important to be able to predict performance variations due to bending. We propose novel models which allow to predict the deterministic and statistical variation in resonance frequency of rectangular wearable patch antennas. They consist of an analytical model for cylindrical-rectangular patch antennas, expressing resonance frequency as a function of the bending radius, and a novel technique based on polynomial chaos, that quantifies statistically the variations of the resonance frequency under randomly varying bending conditions. The proposed models have been experimentally and numerically verified, and proven to be much faster and computationally less expensive than traditional techniques based on EM solvers and Monte Carlo simulations, making them very advantageous tools for the design and characterization of body-worn patch antennas

Circularly Polarized Square Patch Antenna with Trimmed Corners Using Textile Material

ABSTRACT: In this paper a circularly polarized wearable antenna at 2.4 GHz has been proposed for navigation, military communication, body centric communication and medical emergency. Body centric communication is an important application in the field of wireless communication and since antenna can be implemented on textile material, hence it can be widely used for military communication also. The paper presents the design of the wearable antenna made by the use of jeans substrate textile material with thickness 1mm, dielectric constant 1.7 and loss tangent 0.02. To feed the antenna inset feeding with a quarter wave transformer has been used. The proposed antenna offers approx -20 dB reflection loss, approx 3.5 dB axial ratio and 29% antenna efficiency