Thesis Defense - Mustafa Ayebe (MSEE)

Mustafa Ayebe – M.Sc. Electrical & Electronics Engineering

Asst. Prof. Ahmed Akgiray – Advisor

Date: 25.07.2022

Time: 15.00

Location: AB1 231

“Design of Vivaldi Antenna Operating in Two Frequency Bands with Distinct Polarizations”

Asst. Prof. Ahmed Akgiray, Özyeğin University

Asst. Prof. Hüseyin Şerif Savcı, Istanbul Medipol University

Asst. Prof. Kadir Durak, Özyeğin University

Abstract:

This thesis presents a novel dual-polarized antenna design based on two orthogonally place Vivaldi antenna elements and is driven by a specially designed feeding network that splits the incoming signals into two wherein one of them is linearly polarized between 4 and 6 GHz and the other one is circularly polarized from 14.5 to 15.5 GHz. Splitting of the input signal into the two frequency bands, a diplexer is designed. A Wilkinson power divider and a transmission-line phase shifter are employed to realize phase differences to achieve circular polarization at the upper-frequency band. The feed network is integrated with the Vivaldi elements to ensure a compact form factor critical for reflector applications. In order to avoid the crossing of two microstrip-to-slotline transitions of the Vivaldi elements, a small shift between them is introduced. This antenna is intended to be used as a feed antenna for reflector systems employed in radio link systems of drones. The combination of these distinct frequency bands with different polarization requirements allows the use of a single ground control antenna instead of two independent antennas thereby reducing cost and space requirements.

 For demonstration purposes, a prototype is fabricated. The antenna achieves better than -15 dB input reflection coefficients over most of the operating bands and the axial ratio is less than 2 dB for the upper-frequency range. The antenna exhibits gain between 7.2 to 9.5 dBi from 4 to 16 GHz. Meanwhile, stable radiation patterns are achieved with the cross-polarization lower than -25 dB across the operating bands in the boresight direction.

Bio:

Mustafa Ayebe received a B.Sc. degree in Electrical and Electronics Engineering from Özyeğin University in 2020. He is currently pursuing his Master of Science under the supervision of Asst. Prof. Ahmed Akgiray at Özyeğin University. His research interests lie in microwave circuits and systems, electromagnetics, antennas, and wireless communication systems.