Public defence, Radio Science and Engineering, MSc Mostafa Movahediqomi

The title of the thesis: Metasurface-Based Technologies for Next-Generation Wireless Communication Systems

Thesis defender: Mostafa Movahediqomi
Opponent: Prof. Anthony Grbic, University of Michigan, US
Custos: Prof. Viktar Asadchy, Aalto University School of Electrical Engineering

Metasurfaces could make future wireless networks smarter, more adaptable and easier to deploy

The rapid growth of connected devices and services is creating increasing demand for faster, more reliable and energy-efficient wireless communication. Instead of improving only transmitters and receivers, future networks may also actively control how radio waves travel through the surrounding environment. This doctoral thesis investigates how metasurfaces—thin engineered surfaces capable of manipulating electromagnetic waves—can contribute to this development.

The research addresses three areas of future wireless communication. First, it investigates reconfigurable intelligent surfaces (RISs), which can redirect radio waves toward desired locations. Such surfaces could, for example, improve coverage in areas where buildings or other obstacles block a direct wireless connection. The thesis develops RIS solutions that can not only redirect a signal efficiently but also estimate the direction from which an unknown user's signal arrives. This enables communication and sensing to be performed simultaneously using the same surface, an important capability envisioned for future 6G networks.

Second, the thesis develops an ultrathin and flexible metasurface antenna concept for satellite communications. The proposed approach is intended to support lightweight and potentially foldable antennas, which could simplify the deployment of large antenna surfaces in space.

Finally, the research explores metasurfaces whose properties change over time. These structures can create nonreciprocal behaviour—allowing electromagnetic waves to be controlled differently depending on their direction of propagation—without conventional magnetic materials. The work demonstrates concepts for important microwave functions such as isolators and circulators.

Overall, the thesis shows how controlling electromagnetic waves in space and time can provide new tools for designing smart wireless environments, compact radio-frequency components and deployable satellite antennas. These technologies could contribute to more adaptable terrestrial and satellite communication systems beyond 5G and toward 6G.

Key words: Beyond 5G, 6G, perfect anomalous reflection, reconfigurable intelligent surface (RIS), all angle scanning, integrated sensing and communication (ISAC), spatial modulated metasurface, leaky-type antenna, temporal stacked metasurface, isolator, circulator

Thesis available for public display 7 days prior to the defence at Aaltodoc. 

Contact: mostafa.movahediqomi@aalto.fi