Thesis Defense - Ecmel Mehmet Ceter (MSEE)

Ecmel Mehmet Ceter – M.Sc. in Electrical and Electronics Engineering

Asst. Prof. Göktürk Poyrazoğlu – Advisor

Date: 06.08.2025

Time: 16.00

Location: AB1 245

“OPTIMIZATION OF FRACTAL ANTENNAS FOR RFID AND WIRELESS COMMUNICATION”

Asst. Prof. Göktürk Poyrazoğlu, Özyeğin University

Prof. Dr. Hüseyin Arda Ülkü, Yeditepe University

Asst. Prof. Ahmed Akgiray, Özyeğin University

Abstract:

This thesis presents the design, simulation and comparative performance analysis of a multiband fractal antenna based on the third iteration of the Koch curve, intended for Radio Frequency Identification (RFID) and wireless communication systems. The study explores how substrate material properties, particularly dielectric constant and loss tangent, influence antenna performance by implementing the same antenna geometry on two substrates: conventional FR-4 and high permittivity Alumina (Al2O3). The antenna structures were modeled and optimized using the Ansys HFSS (High Frequency Structure Simulator), with comprehensive parametric sweeps conducted to evaluate the impact of critical design parameters, including ground plane dimensions, feedline width and patch height. The designs were evaluated in terms of return loss (S11), Voltage Standing Wave Ratio (VSWR), bandwidth, radiation patterns (2D and 3D) and gain across multiple frequency bands. Simulation results indicate that the use of Alumina, with its relative permittivity of εr ≈ 9.8, enables considerable size reduction of the antenna while maintaining acceptable radiation efficiency and multiband performance. Conversely, the FR-4 based design, with εr ≈ 4.4, provides broader bandwidth but at the cost of increased physical dimensions. The results further demonstrate that the Alumina based design exhibits sharp resonance characteristics suitable for compact UHF RFID tag or reader integration, whereas the FR-4 design provides wide bandwidth, allowing tolerances to be disregarded during application. The antennas achieved resonant frequencies at approximately 866 MHz, 2.4 GHz and 5.8 GHz, making them suitable for EPC Gen2 RFID, Wi-Fi and industrial wireless applications. The use of a fractal geometry not only enabled size reduction but also facilitated multiband operation due to the self similarity and space filling characteristics inherent in the Koch structure. This work contributes to the field of substrate aware antenna engineering by offering a systematic comparison between low and high permittivity materials in fractal antenna design and provides design guidelines for selecting suitable substrates based on size, frequency and bandwidth requirements.

Bio:

Ecmel Mehmet Ceter received his Bachelor’s degree in Electrical and Electronics Engineering from Dokuz Eylül University in 2019. He commenced his professional career at Vestel Electronics in 2020 while pursuing his master’s degree at Özyeğin University, where he conducted his thesis research under the supervision of Asst. Prof. Göktürk Poyrazoğlu. After gaining five years of experience in the automotive sector, he joined the defense industry company ASELSAN, where he currently works as a Test and Analysis Engineer.