2023-03-14

Qiuyan Liang. Photo: Yuyan Cao.

Wireless transmissions can be drastically improved by antennas with high gain and beam steering capability. Qiuyan Liang has investigated how such antennas can be designed in an efficient manner.   On March 24 at 9.15 she defends her PhD thesis “Low-Complexity Multiband and Beam-Reconfigurable Antennas for Beyond 5G Communications” at LTH, Lund University.

Read more about the dissertation.
Download the thesis.

What is your thesis about?

Nowadays the use of wireless internet has permeated many aspects of our lives, including study, work, travel, and entertainment. These ever-more-complex contents transmitted in wireless communication networks are essentially in the form of data, and ever-increasing data rates are needed to support the content delivery. The communication of information requires a transmitter and a receiver. For example, if someone transmits information by speech or body language, then the information can be received by another person’s ears or eyes. Similarly, wireless communication also requires a transmitter and a receiver, with an antenna being a critical component in each. Antennas with large frequency bandwidth, high gain, and beam steering capability are very important 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. Therefore, this thesis focuses on the low-complexity multiband and beam-reconfigurable antenna design for the two applications.

Antennas based on partially reflective surface (PRS) can provide high gain with simple structure and low cost, which have good potential for application in future base stations. The first topic of this thesis is on enhancing two aspects of PRS antenna design, namely beam steering capability and shared-aperture antenna design. Existing PRS antennas mainly use standard reconfigurable approaches for beam steering, e.g., using reconfigurable loads on the PRSs’ unit cells. The beam can be pointed towards different directions in different reconfigurable states. However, current beam-reconfigurable PRS antennas suffer from narrow coverage range, distorted beam shape and considerable gain variations over the beams in different directions, which may lead to degradation of communication quality. On the other hand, shared-aperture antenna design with PRS aims to integrate antennas working at different frequency bands into a shared space to provide high space utilization. However, existing design schemes suffer from inflexible frequency ratio (of the bands) and bulky antenna structures. Therefore, the main part of my thesis deals with the research question on how to solve the challenges encountered by PRS antennas with respect to beam reconfigurability and shared aperture designs, while maintaining low-complexity structures.

Figure 1: Base station and user device antennas in high frequency applications need to be capable of beam steering with high gain.

Besides base stations with fixed installations, wireless communication networks consist of a large number of user devices, including mobile terminals. With the rollout of 5G, terminal antennas are being developed to cover both existing and new 5G frequency bands, spanning both sub-6GHz bands and mm-wave bands. To save antenna implementation space, it is desirable to co-design and even co-locate these antennas. However, existing co-design approaches suffer from complex structure of the mm-wave antenna and low space utilization. Therefore, the other part of my thesis is about solving the research question on how to co-design the sub-6GHz and mm-wave antennas for mobile terminals for compactness and low-complexity.

How will your results be of use in the future?

Antennas have already been widely applied in practice and a larger number of antennas will be deployed in future wireless communication networks. My research provides low-complexity PRS antenna designs for base stations and co-designed antennas for mobile terminals. Therefore, I believe that the results from my research have the potential to contribute to the development of more cost-effective wireless communication networks by improving system architecture and saving installation resources.