Public defence in Radio Engineering, M.Sc.(Tech.) Veli-Pekka Kutinlahti

The title of the thesis: Antenna mutual coupling and amplifier effects in transmission

Doctoral student: Veli-Pekka Kutinlahti
Opponent: Prof. Daniel Sjöberg, Lund University, Sweden
Custos: Prof. Ville Viikari, Aalto University School of Electrical Engineering, Department of Electronics and Nanoengineering

Modern lifestyle relies heavily on wireless communication. Mobile phones and laptops are taken for granted, and internet access is expected to be smooth and continuous. More and more devices, such as the self-driving car, will most likely be connected to the internet in the future. 

With the forthcoming fifth generation, commonly referred to as 5G, telecommunication standard, the architecture of the part responsible for the wireless communication in mobile devices, the transmitter, will experience a drastic change. Transmitters in mobile devices of previous wireless generations usually utilize single amplifier and antenna solutions, while 5G transmitters will utilize multiple amplifiers and antennas. The increase in antenna elements will enable beamsteering, the ability to redirect the wireless signal to a wanted direction towards the receiver. This change in the structure requires careful consideration of how the transmitter is designed and operated, as mobile devices need to be compact, cheap and efficient. Currently research is looking for innovative solutions for both amplifiers and antennas that can deliver the performance required by the 5G. 

The research in this thesis has focused on the co-operation of amplifiers and antennas in antenna arrays while beamsteering. Beamsteering will create a changing environment for the amplifiers which are driving the antennas and alter their operation. This affects the whole transmitter and can cause errors or drop in efficiency. This work presents solutions to use phase and amplitude control to optimize radiation properties in amplifier-antenna systems and to achieve frequency tunable wide-band antennas, how antenna matching network design can utilize amplifier data to improve amplifier-antenna linearity, and a way to improve amplifier-antenna system operation when the amplifier utilizes DC bias control to output lower power. 

The findings in this thesis are in the center of the study of 5G mobile systems and could help in the design of mobile transmitters also in general. Considering the co-operation of both the amplifier and the antenna in the transmitter will likely become a mandatory aspect in the design of 5G transmitters to prevent braking and to guarantee efficient operation of wireless devices.

Keywords: amplifier, antenna, beam-steering, load-pull, mutual coupling

Thesis available for public display 10 days prior to the defence at: https://aaltodoc.aalto.fi/doc_public/eonly/riiputus/

Doctoral theses in the School of Electrical Engineering: https://aaltodoc.aalto.fi/handle/123456789/53