Recent developments and technological advancements in wireless communication, MicroElectroMechanical Systems (MEMS) technology and integrated circuits has enabled low-power, intelligent, miniaturized, invasive/non-invasive micro and nano-technology sensor nodes strategically placed in or around the human body to be used in various applications, such as personal health monitoring. This exciting new area of research is called Wireless Body Area Networks (WBANs) and leverages the emerging IEEE 802.15.6 and IEEE 802.15.4j standards, specifically standardized for medical WBANs. The aim of WBANs is to simplify and improve speed, accuracy, and reliability of communication of sensors/actuators within, on, and in the immediate proximity of a human body. The vast scope of challenges associated with WBANs has led to numerous publications. In this paper, we survey the current state-of-art of WBANs based on the latest standards and publications. Open issues and challenges within each area are also explored as a source of inspiration towards future developments in WBANs.

Wireless Body Area Networks: A Survey

Metasurfaces: From microwaves to visible

Antennas implanted in a human body are largely applicable to hyperthermia and biotelemetry. To make practical use of antennas inside a human body, resonance characteristics of the implanted antennas and their radiation signature outside the body must be evaluated through numerical analysis and measurement setup. Most importantly, the antenna must be designed with an in-depth consideration given to its surrounding environment. In this paper, the spherical dyadic Green's function (DGF) expansions and finite-difference time-domain (FDTD) code are applied to analyze the electromagnetic characteristics of dipole antennas and low-profile patch antennas implanted in the human head and body. All studies to characterize and design the implanted antennas are performed at the biomedical frequency band of 402-405 MHz. By comparing the results from two numerical methodologies, the accuracy of the spherical DGF application for a dipole antenna at the center of the head is evaluated. We also consider how much impact a shoulder has on the performance of the dipole inside the head using FDTD. For the ease of the design of implanted low-profile antennas, simplified planar geometries based on a real human body are proposed. Two types of low-profile antennas, i.e., a spiral microstrip antenna and a planar inverted-F antenna, with superstrate dielectric layers are initially designed for medical devices implanted in the chest of the human body using FDTD simulations. The radiation performances of the designed low-profile antennas are estimated in terms of radiation patterns, radiation efficiency, and specific absorption rate. Maximum available power calculated to characterize the performance of a communication link between the designed antennas and an exterior antenna show how sensitive receivers are required to build a reliable telemetry link.

Implanted antennas inside a human body: simulations, designs, and characterizations

Preface 1. Introduction 2. FDTD Method for periodic structure analysis 3. EBG Characterizations and classifications 4. Design and optimizations of EBG structures 5. Patch antennas with EBG structures 6. Low profile wire antennas on EBG surfaces 7. Surface wave antennas Appendix: EBG literature review.

/pdf/electromagnetic-band-gap-structures-in-antenna-engineering-luh3tdu8zr.pdf

Electromagnetic Band Gap Structures in Antenna Engineering

A simple ground plane structure that can reduce mutual coupling between closely-packed antenna elements is proposed and studied. The structure consists of a slitted pattern, without via's, etched onto a single ground plane and it is therefore low cost and straightforward to fabricate. It is found that isolations of more than -20 dB can be achieved between two parallel individual planar inverted-F antennas (PIFAs) sharing a common ground plane, with inter-antenna spacing (center to center) of 0.116 lambdao and ground plane size 0.331lambdao 2. At 2.31 GHz it is demonstrated that this translates into an edge to edge separation between antennas of just 10 mm. Similarly the structure can be applied to reduce mutual coupling between three or four radiating elements. In addition the mutual coupling between half wavelength patches and monopoles can also be reduced with the aid of the proposed ground plane structure. Results of parametric studies are also given in this paper. Both simulation and measurement results are used to confirm the suppression of mutual coupling between closely-packed antenna elements with our slitted ground plane.

Reduction of Mutual Coupling Between Closely-Packed Antenna Elements

To characterize the performance of implantable biomedical devices, the interactions between the devices and the human body need to be properly assessed Specifically, wireless telemetry systems for biomedical applications require a reliable communication link between the interior device and the exterior equipment for exchange of required data and information This paper mainly deals with the implantable antennas embedded on the head telemeter To generate parametric data, the electromagnetic scattering analysis is confined to the human head and dipole antennas

http://ieeexplore.ieee.org/iel5/9230/29248/01321490.pdf

An implanted antenna in the spherical human head: SAR and communication link performance

Biotelemetry which provides wireless communication links between internal devices and outside equipment is a promising function for future implantable biomedical devices. In order to build reliable wireless links, detailed characterization and performance evaluation of the telemetry links are required. In this work, the finite difference time domain (FDTD) simulations are performed to analyze the radiation performances of small dipole and loop antennas in biological tissues for various biotelemetry links. By comparing the electrical characteristics of vertical and horizontal loop antennas above a perfect electric conductors (PEC) plane, the effects of biomedical devices on biotelemetry links are estimated in terms of radiation efficiency and specific absorption rate (SAR). Finally, it is observed that electromagnetic band-gap (EBG) structures are useful candidates for biotelemetry link design.

/pdf/electromagnetic-interactions-between-biological-tissues-and-3k8qmsa5yi.pdf

Electromagnetic interactions between biological tissues and implantable biotelemetry systems

In this paper, the radiation mechanism of an implanted planar inverted F antenna (PIFA) is studied to improve radiation performances of PIFA in a human body by changing the width of the planar radiators. The PIFA is designed to operate at the medical implant communications service (MICS) frequency band (402-405 MHz). The numerical computational procedures (Annex E of Std. C95.3-2002) recommended by IEEE are applied to calculate spatial-average specific absorption rate (SAR) for the implanted antennas located in a biological tissue model. An experimental setup is used to measure the impedance matching characteristics of the implanted antenna.

SAR reduction of implanted planar inverted F antennas with non-uniform width radiator

Implanted Antennas in Medical Wireless Communications (Synthesis Lectures on Antennas and Propagation)

Based on the FDTD simulations and the return loss measurement setup, a spiral-type microstrip antenna and planar inverted F antenna (PIFA) are optimized to operate in a human body at the biomedical frequency band and their electric characteristics are compared in terms of physical dimension and radiation characteristics. Although the radiation patterns are similar to each other, the PIFA has advantages over a microstrip antenna, specifically smaller dimensions and higher radiation efficiency. The SAR calculation of two low profile antennas indicates that the dielectric layer used for the superstrate are useful to protect the skin tissue in front of the antenna and make it possible for the implanted antenna to deliver more than 25 /spl mu/W for short-range biomedical devices.

Jaehoon Kim

Papers

An implanted antenna in the spherical human head: SAR and communication link performance

Electromagnetic interactions between biological tissues and implantable biotelemetry systems

SAR reduction of implanted planar inverted F antennas with non-uniform width radiator

Implanted Antennas in Medical Wireless Communications (Synthesis Lectures on Antennas and Propagation)

Low-profile antennas for implantable medical devices: optimized designs for antennas/human interactions