Generating multi-beams along with having broadband and beam steering capability in the mm-waves band are of crucial importance for diverse applications such as remote piloted vehicles, satellites, collision-avoidance radars, and ultra-wideband communications systems. Besides, the propagation environment at millimeter wave (mm-wave) frequencies—suggested for the next generation of wireless networks (5G)—lends itself to a beamforming structure wherein antenna arrays are required in order to obtain the necessary link budget and to overcome the associated strong attenuation. Therefore, the design of high gain antennas (to focus the directive beam to a user) and beamforming networks (to reduce interference) are essential and are needed to address many challenges associated with 5G wireless communications.
This work addresses the design and development of high-performance Quasi-Yagi antenna and Rotman lens-based beamforming networks. Accordingly, several issues are addressed in this thesis.
A Quasi-Yagi antenna with a perturbed dielectric lens that is broadband and has high gain is designed, optimized, fabricated and tested at 30 GHz. The antenna provides 95% aperture efficiency with a measured gain of 15 dBi as well as a radiation efficiency of ~90% at 30 GHz and a broadband (24-40 GHz) for |S_11 |<-10 dB. The designed end-fire antenna, with its low-profile and compact size, is a good candidate for many applications in the mm-wave band.
An optimum and accurate methodology for designing Rotman lens-based mm-wave analog beamforming network (BFN) is presented. The simulation and measurement results showed good beamforming capabilities as well as a scanning range of 80° in the azimuth plane, and, also, good matching at the array ports. The maximum phase error is ±6.6°, and the main beam of the proposed BFN points at seven different angular directions that cover the range of ±40°. The maximum achieved realized gain is 14 dBi at 28 GHz for the center beam.
An analog Rotman lens-based BFN using RWG technology, integrated with the excitation ports and the antenna array elements, was designed, simulated, manufactured, and measured. The proposed integrated system is realized using the metallized 3D-printing technology, in order to reduce the implementation cost of the full metal RGW Rotman lens. The measured results demonstrate that the system scan range equals ±39.5º over a wideband 27.5-37 GHz decreases to 30º in the band 37-40 GHz. The BFN bandwidth for VSWR < 2 is larger than 38% and is limited by its single antenna element
