2023-05-16

Photo: H. Mirhajian

Hanieh Aliakbari has used systematic, modal design to improve antenna bandwidth. She defends her thesis Wednesday, June 14th, E:1406, the E-house, 09:15.

Link to thesis.

Link to webinar (Zoom)

What is your thesis about?

Today's society relies more and more on the communications of various contents, especially in the form of data, with wireless communications taking the center stage. The most common form of wireless communications, mobile communications, is changing people’s lives over the entire world. One example is the number of smartphone users that grows by hundreds of millions every year, many of whom do not previously have access to telephony or the many opportunities and conveniences it brings. Simultaneously, due to the popularity of bandwidth-hungry streaming video apps, the traffic generated by existing devices also increases by 30-40% annually. In addition, new wireless application areas are also emerging. For example, autonomous vehicles and drones must communicate with their surroundings to avoid collisions and other incidents. To support these different complex contents in wireless networks, higher data rates are needed.

Antenna is a critical component in wireless communications networks as it has the role of sending or receiving the aforementioned data as wireless signals over the air, which eliminates the need for wires. The wireless signals propagate through the medium or channel between the antennas at the transmitter and receiver in the form of electromagnetic waves. In my research, I utilized an antenna design paradigm based on modal methods to meet the antenna requirements for modern wireless systems and achieve higher data rates. Basically, in modal analysis, an antenna’s complex response is described by the weighted sum of multiple rather simpler responses called modes, with the modes being easier to characterize. This results in a more systematic design procedure, which is different from the traditional antenna design framework that mainly relies on intuition from past design experiences and blind numerical optimization of structural parameters.

Following the demand for ever increasing data rates, the antennas in mobile communication systems are required to provide more features and higher performance. One trend is to employ advanced multi-antenna technology to provide high data rates and link reliability. In this context, the first track of my research deals with some fundamental challenges of multi-antenna design for smartphones. The second trend to provide higher data rates for wireless communication is to move towards higher frequencies such as millimeter wave (mm-wave) bands in 5G due to the much larger bandwidths available in those bands than sub-6 GHz bands.  Therefore, the second track of my research investigates new concepts in integrated antennas for mm-wave wireless communications and/or radar systems using different modal theories.

Here the three different “modes” of a conducting rectangular plate are illustrated, which could be a simplified model of a handset’s metal chassis i.e., the printed circuit board (PCB).

What is the most fascinating or interesting with your thesis subject?

Clear and intuitive explanations should be provided for various electromagnetic phenomena observed during the process of antenna design. Such insights are essential to achieve better antenna performance. The common problem in traditional antenna design strategies is that they do not directly provide useful physical insights of the radiating structure or its operating principles, and hence it is difficult to provide rigorous antenna design guidelines. On the other hand, the design strategy that I adopted to solve different antenna design problems in my thesis utilizes the concept of electromagnetic “modes” to mitigate the previous limitations. These modes offer physical explanations to the (modal) behavior of the antenna system, which can then yield systematic guidelines for antenna design. In some special types of modal theories, analysis of arbitrary shape structures is possible. Furthermore, a predefined excitation is not required for the modal-based strategy. In contrast, excitation types and positions in traditional antenna design are found through visual inspection and analysis of excited currents of similar antennas, or by means of trial-and-error excitation placement.

What are your plans?

My passion has always been to pursue a career in academia. However, as a researcher, I have also been very interested in having close collaboration with reputable companies and solving real-world issues, as it would make a direct positive impact on society. Therefore, from last year I started working in Volvo Car Corporation (VCC) as a researcher and I am applying the knowledge that I have gained from my research studies for antenna system design, which has become a key aspect in developing the next generation of premium cars.