PhD defence: Low-Complexity Multiband and Beam-Reconfigurable Antennas for Beyond 5G Communications
Plats: E:1406, E-huset, Ole Römers väg 3, LTH, Lund University, Lund, and online
Kontakt: buon_kiong [dot] lau [at] eit [dot] lth [dot] se
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Thesis title: Low-Complexity Multiband and Beam-Reconfigurable Antennas for Beyond 5G Communications
Author: Qiuyan Liang, Department of Electrical and Information Technology, Lund university
Faculty opponent: Professor Sean Victor Hum - Canada.
Location: E:1406 E-huset, Ole Römers väg 3, LTH, Lund University, Lund.
Streamed at: https://lu-se.zoom.us/s/64926871940
Antennas with large frequency bandwidth, high gain, and beam steering capability are very importance for future wireless communication systems. However, it is very challenging to design antennas with low-complexity structures and high space utilization that can achieve these desired features. Base stations with fixed installations and non-stationary mobile terminals play critical roles in wireless communication networks. The research in this thesis focuses on the low-complexity multiband and beam-reconfigurable antenna design for the two applications.
The first topic of this thesis is about partially reflective surfaces (PRS) antennas, which have significant potential for application in future base stations. In the first part (Part I) of this thesis, existing PRS antennas and challenges to be addressed in PRS antenna design are introduced with respect to beam steering capability and shared-aperture antenna design. To give a clearer insight into the working principle of PRS antenna as well as several observed phenomena involving PRS, the existing theory for PRS antenna is extended. Ray-tracing models as well as the theory of PRS unit cells are utilized to explain the operation of PRS antennas that generate broadside and/or deflected beams. Using these tools, two practical PRS antennas are designed for beam reconfigurability and shared-aperture implementation, respectively. In the first work, we compare the beam deflection capability of different types of PRSs using ray-tracing analysis, with the aim of providing a guideline for selecting a suitable PRS type that would yield a larger beam steering range. In addition, the role of a feeding source in enhancing beam deflection of PRS is explained using ray-tracing analysis, and a beam-reconfigurable feeding source with low-complexity structure is presented. In the second work, we derive the frequency ratio gap for traditional dual-band shared-aperture Fabry-Pérot cavity (DS-FPC) antennas with single-layer PRS and subsequently present a shared-aperture antenna design method with flexible frequency ratio to fill the gap.
The second topic of this thesis is on the co-design of mobile terminal antennas that can cover a wide range of frequency bands. Such antennas are of significant current interest due to the current trend of utilizing higher frequency spectra in wireless communication. A co-designed millimeter-wave (mm-wave) and sub-6GHz antenna system is conceived, where the mm-wave antennas that offer reconfigurable beams for beam steering are integrated into the capacitive coupling elements (CCEs) of the sub-6GHz antenna. Such an implementation aims to achieve a compact and low-complexity antenna structure. In addition, several techniques have been investigated by simulation to achieve further performance improvements in the proposed antenna system with respect to mm-wave antenna gain and bandwidth as well as sub-6GHz antenna tunability and bandwidth.