Design and development of circularly polarized millimeter wave antennas

Abstract

With the evolution of wireless technologies, the unending demands of higher data rates and faster internet access has also been increased. Fourth generation (4G) technologies have been employed to meet the demand of higher data rates, but it is not enough to incorporate ever increasing number of users and high data rate requirements. This demand has led us to move to 5th generation wireless communication and millimeter-wave (mm-wave) spectrum. The term mm-Wave refers to a portion of the radio frequency (RF) spectrum with a very short wavelength that lies between 24 GHz and 100 GHz. This promising 5G technology is critical not only for achieving the rapidly increasing data rate demands, low power consumption, and reliability for an ever-increasing number of connected devices, but also for enhancing the capabilities of emerging technologies such as smart cities, Internet of Vehicles, and virtual reality. As mm-wave frequencies have small wavelengths, a large number of antenna elements can be deployed in the same form factor, resulting in high spatial processing gains that can theoretically compensate for at least the isotropic path loss. This thesis presents a planar, low profile, high gain circularly polarized microstrip patch antenna for millimeter-wave (mm-wave) wireless communication in Ka-band (26-40 GHz) applications. The single antenna element exhibits an impedance bandwidth (reflection coefficient < -10 dB) of 1.43 GHz (27.8–29.23 GHz) and an axial ratio (AR) bandwidth of 600 MHz (27.93 – 28.53 GHz). While designing the 1×4 antenna array, the geometry produces an impedance bandwidth of 1.74 GHz (27.79- 29.53 GHz) with an AR bandwidth of 350 MHz (28.75 -28.40 GHz). In addition, the array exhibits a large gain of 13.21 dBic as compared to 7.62 dBic gain of its single element. The proposed design has a compact size, simple topology, and broadside radiation. The concept is explained through parametric variation, current distribution, and radiation pattern. This thesis aims to design and analyze circularly polarized millimeter wave antennas. This thesis covers the study of the fundamentals of antennas and microstrip patch antennas, followed by a series of analyses of CP antenna designs. A brief study of the patch antenna is carried out to understand its working and effect on truncation and etchings design. Different CP antenna configurations were carefully analyzed based on CP antenna key parametric and convention performance metrics, reflection coefficient, radiation pattern, and gain. The analysis is further carried out to design a dual-band antenna incorporating cross slot etching as the constituent element. In our work, a novel method is used to design a dual-band circularly polarized patch antenna for mm-wave applications using multiple layers of substrates. Also, an array structure for a single-band CP antenna has been designed to get high gain using a Wilkinson power divider. Furthermore, this work can be extended by creating an array structure for the final proposed design and by choosing the dual bands adjacent to each other; an ultra-wideband structure can also be designed upon further modification of the structure.