Worcester Polytechnic Institute Electronic Theses and Dissertations Collection

Title page for ETD etd-011514-100647


Document Typethesis
Author NameElloian, Jeffrey
URNetd-011514-100647
TitleTheoretical and Numerical Analysis of a Novel Electrically Small and Directive Antenna
DegreeMS
DepartmentElectrical & Computer Engineering
Advisors
  • Sergey Makarov, Advisor
  • Ara Nazarian, Committee Member
  • Vishwanath Iyer, Committee Member
  • Yehia Massoud, Department Head
  • Keywords
  • Microwave Tomography
  • Small Antennas
  • Electromagnetics
  • Antenna Design
  • Date of Presentation/Defense2014-01-17
    Availability unrestricted

    Abstract

    Small antennas have attracted significant attention due to their prolific use in consumer electronics. Such antennas are highly desirable in the healthcare industry for imaging and implants. However, most small antennas are not highly directive and are detuned when in the presence of a dielectric. The human body can be compared to a series of lossy dielectric media.

    A novel antenna design, the orthogonal coil, is proposed to counter both of these shortcomings. As loop antennas radiate primarily in the magnetic field, their far field pattern is less influenced by nearby lossy dielectrics. By exciting two orthogonal coil antennas in quadrature, their beams in the H-plane constructively add in one direction and cancel in the other. The result is a small, yet directive antenna, when placed near a dielectric interface.

    In addition to present a review of the current literature relating to small antennas and dipoles near lossy interfaces, the far field of the orthogonal coil antenna is derived. The directivity is then plotted for various conditions to observe the effect of changing dielectric constants, separation from the interface, etc.

    Numeric simulations were performed using both Finite Difference Time Domain (FDTD) in MATLAB and Finite Element Method (FEM) in Ansys HFSS using a anatomically accurate high-fidelity head mesh that was generated from the Visible Human Project® data. The following problem has been addressed: find the best radio-frequency path through the brain for a given receiver position – on the top of the sinus cavity. Two parameters: transmitter position and radiating frequency should be optimized simultaneously such that (i) the propagation path through the brain is the longest; and (ii) the received power is maximized. To solve this problem, we have performed a systematic and comprehensive study of the electromagnetic fields excited in the head by the aforementioned orthogonal dipoles. Similar analyses were performed using pulses to detect Alzheimer’s disease, and on the femur to detect osteoporosis.

    Files
  • jelloian.pdf

  • Browse by Author | Browse by Department | Search all available ETDs

    [WPI] [Library] [Home] [Top]

    Questions? Email etd-questions@wpi.edu
    Maintained by webmaster@wpi.edu