Reconfigurable Wideband Circularly Polarized Antenna Array for 5G mm-Wave Applications

Abstract

In this thesis, a novel reconfigurable wideband circularly polarized antenna array structure designed for millimeter-wave 5G applications at Ka-band is proposed. The system offers dynamic polarization control and the ability to switch between right-hand circular polarization (RHCP) and left-hand circular polarization (LHCP), enabling enhanced communication flexibility. The design is realized through the implementation of a 2x2 antenna array structure as a radiating element, a 90° hybrid coupler, a 180° rat-race coupler with cross-over, and an SPDT switch. The primary structure of the patch antenna is based on two dual-fed microstrip lines at the center of the orthogonal edges of the patch antenna. A four-element antenna array based on the structure of the single antenna element is designed to enhance the gain. A quadrature 90° -3dB hybrid coupler is incorporated to evenly split the power and achieve a 90° phase difference between the adjacent antenna elements in the antenna array. In addition, to realize an overall reconfigurable structure with dynamic feeding, a 180° coupler with crossover is utilized to achieve a 180° between two diagonally opposite ports of the hybrid coupler. The overall final structure is reconfigured to attain RHCP or LHCP through the activation of one of two ports. An overall impedance bandwidth of 5 GHz between 30 GHz – 35 GHz, with an overlapping axial-ratio bandwidth of 3.4 GHz between 30 GHz – 33.4 GHz, and a maximum peak gain of 8dBic is achieved.