Novel Magneto-Electric Dipole Antennas for Wideband Wireless Systems

Abstract

Antennas with high specifications attract the interest of researchers in academia and the wireless communications industry. Magneto-electric (ME) dipole antennas are an innovative solution accommodating high antenna system requirements. The operational principle of ME dipoles involves the orthogonal orientation of electric and magnetic dipoles, both excited with equal power and phase. This careful arrangement ensures that the resulting radiation patterns are unidirectional and exhibit identical characteristics in the E- and H-plane. This thesis introduces a circularly polarized circular magneto-electric dipole (CPME) design to reduce the in-band axial ratio (AR). The study transforms the radiating element shape from a square to a circular form to improve the radiation characteristics. To enhance the axial ratio (AR) of the circular CPME dipole without modifying its geometry, we propose two approaches. The first method involves incorporating rectangular slots on the electric dipoles that will increase the electrical length of the electric dipole. The second method uses varying slot gap widths to generate two different magnetic dipole resonances. These methods fine-tune the four ME-dipole modes while preserving the performance and ground plane size. Finally, A new cavity-less magneto-electric dipole antenna is introduced, which uses a suspended transmission line to feed the two dipoles through proximity coupling. The electric dipole operates at a lower frequency band, while the magnetic dipole operates at a higher band, resulting in a wide impedance bandwidth and high realized gain. The antenna is fed by a vertical coaxial cable and a horizontal suspended transmission line, eliminating the need for quarter-wave cavity walls to excite the magnetic dipole. Consequently, the antenna achieves stable radiation characteristics, including wide impedance bandwidth, high and stable gain, a unidirectional radiation pattern with consistent characteristics in both the E- and H-planes and low back-lobe radiation, making it suitable for modern wireless communication systems with simple antenna geometry.