Design and Analysis of Beam Steering Antennas for Next-Generation Wireless Communication
Authors: Kausar Shafaq 
Published: September 2022

Reconfigurable antennas have gained immense interest since the last few decades. Reconfigurable antennas can steer beams dynamically in response to the signal environment, they can also support multiple simultaneous beams. This research work aims to make considerable advancements in the design and analysis of low cost and low power beam steerable antennas. It focuses on the design and demonstration of several prototypes with advanced functionalities, such as passive (broadband, multi-beam, shapable beams) and active (electronically reconfigurable) antennas. The first part of this dissertation covers the design and development of passive metamaterial based multibeam antenna at 30 GHz. Designed antenna is capable of independently steering multiple beams in the azimuth and elevation plane by the two dimensional displacement of feed radiators placed in front of the passive meta-surface. The meta-surface acts as an electromagnetic lens. The unit cell of the meta-surface consists of three layers of Rogers 5880 substrate and four layers of etched copper. The unit cell is designed such that the phase of unit cell transmission coefficient is varied from 0 to 360 degrees by changing the length of the etched copper pattern. As a proof of concept, a multi-layered meta-surface is designed by using conventional uni-focal phase distribution. Multi-beam steering of 0 to 360 degrees in azimuth plane and +/− 40 degrees in elevation plane has been achieved. Antenna peak gain is 34.5 dBi at 30 GHz, the 3 dB bandwidth is from 28.5 to 32.2 GHz. In the next stage scan loss was optimized by synthesizing the meta-surface with bi-focal phase distribution. The scan range of antenna was further extended by designing the multi-facet transmitarray, which increased the scan range to +/−80 degrees. The designed antenna supports multiple-input and multiple-output (MIMO), this introduces diversity and provides an additional degree of freedom to overcome losses at mm-Wave frequencies. This is a mission enabling technology as the antenna supports seamless hand-off between multiple users by forming high gain independently steerable beams. Comparable antennas to the date are low gain, bulky, have limited number of beams and a narrow field of view. Due to absence of active components the designed antenna is low cost and robust. Moreover, the substrate is selected such that the antenna can withstand harsh deep space environmental conditions and it can be folded for easy deployment. Due to potentially low fabrication cost and ability to support MIMO, the designed antenna is a good candidate for next generation satellite communication and mm-Wave 5G systems. The second part of the work covers the design of a novel reconfigurable metasurface antenna to achieve low power and low-cost electronic beam steering. Initially, the unit-cell loaded with varactor diode for dynamic phase control was designed and experimentally validated. The unit cell consists of unique single layered geometry, phase agility of 360 degree has been achieved by tuning varactordiode. The unit-cell was then used to design the reconfigurable reflectarray antenna comprising 14 × 14 unit cells and 196 varactor diodes. A prototype was realized and characterized. Designed antenna has a maximum gain of 19 dBi with beam steering of +/−60 degrees in elevation plane and 360 degrees in azimuth plane.