Divya Kurup

Design of an Implantable Slot Dipole Conformal Flexible Antenna for Biomedical Applications

We present a flexible folded slot dipole implantable antenna operating in the Industrial, Scientific, and Medical (ISM) band (2.4-2.4835 GHz) for biomedical applications. To make the designed antenna suitable for implantation, it is embedded in biocompatible Polydimethylsiloxane (PDMS). The antenna was tested by immersing it in a phantom liquid, imitating the electrical properties of the human muscle tissue. A study of the sensitivity of the antenna performance as a function of the dielectric parameters of the environment in which it is immersed was performed. Simulations and measurements in planar and bent state demonstrate that the antenna covers the complete ISM band. In addition, Specific Absorption Rate (SAR) measurements indicate that the antenna meets the required safety regulations.

In-body Path Loss Model for Homogeneous Human Tissues

A wireless body area network (WBAN) consists of a wireless network with devices placed close to, attached on, or implanted into the human body. Wireless communication within human body experiences loss in the form of attenuation and absorption. A path loss (PL) model is thus necessary to identify these losses in homogeneous medium which is proposed in this paper. The model is based on 3-D electromagnetic simulations and is validated with measurements. Simulations are further extended for different relative permittivity εr and conductivity σ combinations spanning a range of human tissues at 2.45 GHz, and the influence of the dielectric properties on PL is investigated and modeled. This model is valid for insulated dipole antennas separated by a distance up to 8 cm. Furthermore, PL in homogeneous medium is also compared with the path loss in heterogeneous tissues. The path loss model for homogeneous medium is the first in-body model as a function of εr, σ, and separation between antennas and can be used to design an in-body communication system.

Real human body measurements, model, and simulations of a 2.45 GHz wireless body area network communication channel

In this paper, the propagation channel between two half-wavelength dipoles at 2.45 GHz, placed near a human body is studied. Measurements are performed on a real human, considering different parts of the body separately. The measurement results are compared with FDTD simulations, using an anatomically correct model of the human body. Channel characteristics are extracted from the measurement and simulation data. A semi-empirical path loss model is proposed and lognormal behaviour is validated.

Compliance boundaries for multiple-frequency base station antennas in three directions.

In this article, compliance boundaries and allowed output powers are determined for the front, back, and side of multiple-frequency base station antennas, based on the root-mean-squared electric field, the whole-body averaged specific absorption rate (SAR), and the 10 g averaged SAR in both the limbs and the head and trunk. For this purpose, the basic restrictions and reference levels defined by the International Commission on Non-Ionizing Radiation Protection (ICNIRP) for both the general public and occupational exposure are used. The antennas are designed for Global System for Mobile Communications around 900 MHz (GSM900), GSM1800, High Speed Packet Access (HSPA), and Long Term Evolution (LTE), and are operated with output powers at the individual frequencies up to 300 W. The compliance boundaries are estimated using finite-difference time-domain simulations with the Virtual Family Male and have been determined for three directions with respect to the antennas for 800, 900, 1800, and 2600 MHz. The reference levels are not always conservative when the radiating part of the antenna is small compared to the length of the body. Combined compliance distances, which ensure compliance with all reference levels and basic restrictions, have also been determined for each frequency. A method to determine a conservative estimation of compliance boundaries for multiple-frequency (cumulative) exposure is introduced. Using the errors on the estimated allowed powers, an uncertainty analysis is carried out for the compliance distances. Uncertainties on the compliance distances are found to be smaller than 122%.

In-to-Out Body Antenna-Independent Path Loss Model for Multilayered Tissues and Heterogeneous Medium

In this paper, we investigate multilayered lossy and heterogeneous media for wireless body area networks (WBAN) to develop a simple, fast and efficient analytical in-to-out body path loss (PL) model at 2.45 GHz and, thus, avoid time-consuming simulations. The PL model is an antenna-independent model and is validated with simulations in layered medium, as well as in a 3D human model using electromagnetic solvers.

In-body path loss models for implants in heterogeneous human tissues using implantable slot dipole conformal flexible antennas

A wireless body area network (WBAN) consists of a wireless network with devices placed close to, attached on, or implanted into the human body. Wireless communication within a human body experiences loss in the form of attenuation and absorption. A path loss model is necessary to account for these losses. In this article, path loss is studied in the heterogeneous anatomical model of a 6-year male child from the Virtual Family using an implantable slot dipole conformal flexible antenna and an in-body path loss model is proposed at 2.45 GHz with application to implants in a human body. The model is based on 3D electromagnetic simulations and is compared to models in a homogeneous muscle tissue medium.

In-body path loss model for homogeneous and heterogeneous human tissues

An in-body path loss model in homogeneous human tissues is proposed based on 3D electromagnetic simulations and validated with measurements. Simulations are further extended for different relative permittivity and conductivity combinations spanning a range of human tissues at 2.45GHz, and the influence of the dielectric properties on path loss is investigated and modeled. Finally, path loss in homogeneous medium is compared with the path loss in a heterogeneous human phantom.

Simulation of path loss between biocompatible antennas embedded in homogeneous human tissues and comparison of their specific absorption rate

A Wireless Body Area Network (WBAN) is a network, consisting of nodes that communicate wirelessly and are located on or in the body of a person. In this paper, we study the wave propagation using biocompatible folded slot dipole antennas within various lossy human tissues such as the muscle tissue, skin and the fat layer and obtain their path loss (PL) and specific absorption rate (SAR) by means of simulations, and fit a suitable path loss model to the propagation scenario at hand.

Simulation of the path loss between insulated dipoles embedded in homogeneous human muscle tissue

The path loss between insulated dipole antennas in homogeneous human muscle tissue is investigated at 2.457 GHz and an in-body path loss model is derived. Simulations using the FDTD and the MoM methods show excellent agreement. Also, the low values of the deviations demonstrate an excellent agreement between the simulations and models.