Advancements in RF Front-End Efficiency for Next-Generation Communication Systems
Time: Wed 2024-06-05 09.00
Location: Kollegiesalen, Brinellvägen 8, Stockholm
Video link: https://kth-se.zoom.us/j/64147253748
Language: English
Subject area: Electrical Engineering
Doctoral student: Ahmad Emadeddin , Elektromagnetism och fusionsfysik
Opponent: Professor Ville Viikari, Head of Department of Electronics and Nanoengineering, Aalto University, Finland.
Supervisor: Professor B. Lars G. Jonsson, Elektromagnetism och fusionsfysik
QC 20240513
Abstract
The increasing demand for higher data rates and capacity encompasses diverse applications in modern wireless systems. This necessitates addressing the limitations of conventional wireless systems, e.g. bandwidth constraints, efficiency issues, link budget limitations, and size and cost constraints. To achieve high data rates in the gigabit-per-second (Gbit/s), wider bandwidths in the gigahertz (GHz) range are required, leading to a transition to the microwave and millimeter wave (mm-wave) frequency band. However, this transition presents additional challenges, such as increased insertion- and free space path losses. All of these challenges are particularly critical in the Radio Frequency (RF) front-end, which comprises antennas along with other necessary RF elements, e.g. Power Amplifiers (PAs), that play a significant role in determining overall system performance. In this thesis, our research focuses on advancements in RF front-end efficiency— encompassing energy, spectral, size, and cost efficiency— to contribute to meeting the growing demands of next-generation communication systems.
Phased array antennas are widely utilized in modern communication networks to enhance radiation characteristics such as gain and scan capability. Additionally, the direct-integration technique, which removes the need for any intermediate 50 Ω interface impedance, offers improvements in efficiency, size- and cost reduction. This thesis develops active direct-integrated phased array antenna (AIPAA) designs that utilize a combination of wide-scan phased array antennas and direct-integration technique. The presented designs advance the radiation performance through the phased array antenna, enhance the overall efficiency of the antenna and PAs combination via direct-integration, eliminate matching networks' losses through direct-integration, and remove RF switch elements by introducing a half-duplex array. The active integration approach employs an interdisciplinary co-design method to address complex interactions and mutual coupling in the proposed compact-size AIPAAs. In this thesis, the mutual interactions that can impact the system performance have been theoretically and practically discussed in our proposed coupling reduction approach. Besides, a seamless integration of filtering functionality, using proposed periodic structures, into a Vivaldi antenna is employed to design a high-selectivity filtering antenna with wide out-of-band suppression. These proposed designs and approaches help to enhance the performance by improving the spectral- and energy efficiencies, reducing the size, and minimizing costs.
Another approach in this thesis, utilizing irregularly partitioned phased arrays, offers a means to reduce the number of transmitter/receiver modules (system simplification) while maintaining functionality in next-generation wireless systems. An innovative fast-partitioning iterative optimization approach, introduced in the last part of the thesis, overcomes the computational cost/time of phased arrays' exact partitioning while resulting in satisfactory radiation characteristics over wide-scan coverage for large arrays.