Abstract

A Wireless Body Area Network (WBAN) is a system of wireless sensors and devices attached to a person’s body for continuous monitoring of physiological data. These measurements can be used for a variety of purposes such as fitness tracking, personal health management or as medical diagnostic tools. In many cases, WBANs need to communicate with an off-body device to send information to healthcare providers. Wireless Medical Telemetry provides numerous benefits but has a few challenges that need to be overcome. One of the key components in this system is the antenna, which is worn on the body and typically has a broadside pattern directed out. Additionally, flexibility and miniaturization of antennas is crucial for making a comfortable and wearable antenna. Finally, the back radiation must be minimal since the dielectric properties of the human body can significantly affect the return loss, which in turn reduces the gain and distorts the radiation pattern.

The motivation of the present work is based on the need for improving the antenna, for its size, enhanced gain, with small to no back lobe and additionally on a flexible substrate to ensure patient comfort. In the present work, two antennas, a Slotted Dipole Antenna and Inverted-F Antenna have been designed at 2.5 GHz in the Unlicensed Industrial, Scientific and Medical band (ISM). The design and modeling have been done using ANSYS HFSS (High Frequency System Simulator). A Rectangular Patch Artificial Magnetic Conductor (AMC) which is a frequency selective surface has been designed and optimized. Both antennas are backed by this AMC layer to reduce backward radiation and enhance forward gain for off body radiation.

The antennas were fabricated and validated by measurement. Both are on Rogers RT/duroid 5880 substrate (εr = 2.2, tan δ = 0.0009 and dielectric height h = 31mils). The Inverted-F Antenna is significantly smaller than the Slotted Dipole Antenna but has a much lower radiation gain on its own. When the antennas are integrated with the Rectangular Patch AMC their forward gains are very similar. However, the Inverted-F Antenna and AMC has a much larger front to back ratio than the Slotted Dipole Antenna and AMC. The Slotted Dipole Antenna is shown to be flexible, both concave and convex curvature are simulated. In HFSS, the effects of the human body are simulated using the Human Body Model. A SAR analysis is also performed to show the AMC layer not only directs the beam in the desired direction but reduces the amount of power absorbed by the human body significantly. The measured return loss and radiation patterns agree well with simulated results. Lastly, this work proposes an AMC unit cell that is significantly smaller than the Rectangular Patch unit cell, which has the potential to create a smaller AMC layer.

Publication Date

2020

Document Type

Thesis

Student Type

Graduate

Degree Name

Electrical Engineering (MS)

Department, Program, or Center

Electrical Engineering (KGCOE)

Advisor

Jayanti Venkataraman

Advisor/Committee Member

Panos Markopoulos

Advisor/Committee Member

Gill Tsouri

Campus

RIT – Main Campus

Share

COinS