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Christan Elgaard adapted CMOS amplifiers for 5G
Publicerad: 2024-04-15
Title of thesis: Integrated millimeter Wave CMOS Power Amplifiers for 5G Systems.
Link to thesis in Lund University Research Portal.
Defence: Friday April 19th, 09:15, room E:1406. Zoom link. Zoom ID: 63926548525.
Describe your research in...
Title of thesis: Integrated millimeter Wave CMOS Power Amplifiers for 5G Systems.
Link to thesis in Lund University Research Portal.
Defence: Friday April 19th, 09:15, room E:1406.
Zoom link. Zoom ID: 63926548525.
Describe your research in a popular science way
This dissertation focuses on millimeter-wave power amplifiers built using a common and inexpensive silicon-based technology known as CMOS, for fifth-generation mobile systems and beyond. It comprises four scientific publications based on three measured power amplifiers with increasing complexity, where the third one essentially includes a complete transmitter and parts of a receiver. The third circuit is measured with a signal where the power amplifier sends a whopping 9.6 Gbit/s, equivalent to downloading about an hour's worth of video in just one second. To achieve high-output signal transmission at such high data rates without distorting it to the point of making it difficult or even impossible for the receiver to decode the digital bits while consuming as little power as possible, a Doherty amplifier combined with adaptive bias is used. The Doherty amplifier, invented in 1936, has the special property of consuming very little power when amplifying signals with highly varying amplitudes, a characteristic of 5G (and 6G) signals. To save power, the Doherty amplifier has two amplifiers cooperating: one is on all the time (the main amplifier), while the other (the auxiliary amplifier) is only on at high amplitudes, reducing consumption. However, constructing a Doherty amplifier at such high frequencies as millimeter waves poses a significant challenge, making it interesting from a research perspective. To ensure that the transistors amplify the signal in the desired way, it's necessary to set an appropriate operating point, known as biasing the transistors. Normally, a constant operating point is used, but with adaptive bias, the transistors' operating points are adjusted as the signal's amplitude changes. As demonstrated by the research in the dissertation, using a Doherty amplifier with adaptive bias for the auxiliary amplifier is a good way to mitigate the problems that arise when a power amplifier needs to handle the complex signals of 5G and future mobile systems in a power-efficient manner. The fourth article examines and explains the theoretical aspects of how an adaptive bias signal should be designed to work optimally with the auxiliary amplifier, and the article also contains a detailed description of the construction of a circuit capable of creating such an adaptive bias signal and thus able to change the operating point for the auxiliary amplifier very quickly, i.e., with high bandwidth. The circuit creates the adaptive bias signal by first extracting amplitude information from the Doherty amplifier's input signal. An important theoretical result is that an ideal adaptive bias signal should then be constructed through a nonlinear transfer function from the amplitude information. Measurements and simulations show that the circuit effectively achieves this.
The figure shows a die photo of the power amplifier (PA) described in the first paper included in the dissertation. From right to left showing the pre power amplifier (PPA), PPA output resonator, output stage (partly placed under GND bump), and output combiner. The occupied area is 0.144 mm2.
What made you want to pursue a PhD?
Prior to choosing to become a PhD candidate at EIT I held a research position, within the same field and with tight cooperation with my supervisor Henrik Sjöland, at Ericsson research. When the opportunity came to continue the research that I was already conducting at Ericsson, in the form of an industrial PhD linked to EIT, it was an easy decision to accept.
What is the most fascinating or interesting with your thesis subject?
The research and development investments required to launch a global functional cellular network are arguably among the most complex, costly, and far-reaching achievements of mankind. From the complexity and capability of a single transceiver circuit to the complexity of the entire cellular system, one must not overlook the challenges associated with ensuring affordability to enable global widespread access, allowing mobile phones and associated subscriptions to function practically in all corners of the world. At the center of this is the power amplifier and how its limitations are shaping the capacity of the cellular system, and thereby presenting excellent research opportunities.
Do you believe some results from your research will be applied in practice eventually? And if so, how / how?
Yes, I have already seen other published papers in the same field that has used some of the outcome of my research to achieve better performance. I think it is very likely that the proposed idea of using the adaptive bias signal on the auxiliary amplifier of a Doherty amplifier will be used in hardware in both cellular infrastructure and handheld devices.
What are your plans?
My plan is to continue my current position as Master researcher at Integrated Radio and Systems, RF Frontend and Power Amplifiers at Ericsson Research in Lund and hopefully with some form of cooperation with EIT.
Länk till artikeln Christan Elgaard adapted CMOS amplifiers for 5G
Russ Whiton created cellular car navigation for autonomous vehicles
Publicerad: 2024-03-21
Title of thesis: Dude, Where's My Car? Cellular Navigation for Autonomous Driving.
Link to thesis in Lund University Research Portal.
Defence: Wednesday April 10th, 09:15, room E:1406. Zoom link. Zoom ID: 69963010473.
Describe your research...
Title of thesis: Dude, Where's My Car? Cellular Navigation for Autonomous Driving.
Link to thesis in Lund University Research Portal.
Defence: Wednesday April 10th, 09:15, room E:1406.
Zoom link. Zoom ID: 69963010473.
Describe your research in a popular science way
This thesis is a case study in using cellular signals for navigation for a passenger vehicle in environments where GPS is most likely to be unsatisfactory. It touches on many of the important aspects of the problem, starting with how such a navigation technology might be integrated into vehicular electronic systems for advanced use cases like autonomous driving and what challenges need to be overcome if cellular navigation is to work in the environments where satellite navigation also struggles.
A transmitted signal from a cellular base station arrives at a car through several different paths, undergoing different propagation mechanisms for each. Illustration: Max Boerboom.
What made you want to pursue a PhD?
I worked in industry between my Bachelor?s and Master?s, and for 6 years between my Master?s and PhD. It was appealing to me to gain a better theoretical understanding of engineering principles to see problems with more clarity. I also realized that commercialization frequently does not allow for in-depth exploration of subjects, because when something works well enough for deployment it is time to move on to generating new revenue streams.
What is the most fascinating or interesting with your thesis subject?
Navigation as a subject is fascinating. In my thesis, I tried to draw some kind of line from ancient Polynesians navigating using star compasses through to GPS to navigation methods that are novel in 2024 that I developed in this project with my collaborators.
Do you believe some results from your research will be applied in practice eventually? And if so, how / how?
Yes, some of my colleagues in the department are already extending my work for channel modelling. For the navigation methods, I think some form of them might be applied to tracking problems for future cellular networks.
What are your plans?
I bought a Volkswagen Caddy and I?m converting it into a micro-camper. My short-term plan is to rent out my apartment and make a career shift into a life of vagrancy and live in my van, but that choice might be re-evaluated when the temperature drops and the money runs dry.
Länk till artikeln Russ Whiton created cellular car navigation for autonomous vehicles
Niklas Wingren developed software for microwave scattering.
Publicerad: 2024-03-18
Title of thesis: Computational Methods and Measurements for Direct and Inverse Scattering of Microwaves.
Link to thesis in Lund University Research Portal.
Defence: Friday April 5th, 09:15, room E:1406. Zoom link. Zoom ID:...
Title of thesis: Computational Methods and Measurements for Direct and Inverse Scattering of Microwaves.
Link to thesis in Lund University Research Portal.
Defence: Friday April 5th, 09:15, room E:1406.
Zoom link. Zoom ID: 62684643819.
Describe your research in a popular science way
We all use electromagnetic waves in our everyday lives with technologies like mobile phones, contactless payment, and car radars, to name a few. This explosion in wireless technology during the last 30 years or so has, in part, been made possible by the rapid development of computational tools used to simulate electromagnetic waves. It is fair to say that a modern mobile phone, with many antennas hidden inside, would not be possible to design without these tools. My research has focused on situations where electromagnetic waves are scattered by objects, which happens, for example, when an aircraft is located by radar. I have developed computational tools to simulate such situations, and worked with theoretical solutions and real measurements to verify that the computations are correct. I have also combined computational tools with measurements of waves scattered by structural components to locate defects inside the structure.
What made you want to pursue a PhD?
After studying the courses in electromagnetics at LTH I realized that I wanted to learn more, so I looked for a research-adjacent master?s thesis project at the department. This gave me an idea of what it might be like to work as a PhD student, and I decided to apply for a position that was opening up.
Do you believe some results from your research will be applied in practice eventually? And if so, how / how?
The computational software I developed during my time as a PhD student is open source, meaning that it is freely available online for anyone to use. I hope that this will make it useful to others, either directly as a tool or as a basis for other software. Most of my research has also been conducted in collaboration with industry, and there has been interest in my software from their part.
What are your plans?
I will stay at EIT until the summer to, among other things, make my computational software more accessible. After that we?ll see where I might end up.
Länk till artikeln Niklas Wingren developed software for microwave scattering.
Zahra Chamideh improved self-driving cars.
Publicerad: 2024-02-29
Title of thesis: Navigating the Future: Intersection of Safety, Efficiency, and Resilience in Autonomous Traffic Systems. Link to thesis in Lund University Research Portal.
Defence: Tuesday March 12th, 09:15, room E:1406. Zoom link. Zoom ID:...
Title of thesis: Navigating the Future: Intersection of Safety, Efficiency, and Resilience in Autonomous Traffic Systems.
Link to thesis in Lund University Research Portal.
Defence: Tuesday March 12th, 09:15, room E:1406.
Zoom link. Zoom ID: 66179207826.
Describe your research in a popular science way
Imagine a world where your morning commute is no longer a battle with endless red lights and traffic jams. Envision instead a scenario where your car passes through intersections, in seamless conversation with both its vehicular peers and the infrastructure that guides them. This isn't science fiction; it's the emerging reality of autonomous vehicles and intelligent traffic management systems. Across our cities, we're beginning to see glimpses of this future. Smart traffic management systems adjust based on real-time traffic flow, reducing congestion and idling. Autonomous vehicles, already on our roads, promise a future of hands-free, stress-free driving. These advancements are not just about convenience; they're about creating safer, cleaner, and more efficient urban environments.
But what happens when the technologies we rely on face glitches? Picture this: you're in a self-driving car, approaching an intersection. Suddenly, the car's positioning system malfunctions, or it loses the ability to communicate with other vehicles. In such a scenario, the harmonious flow of traffic could be disrupted, leading to confusion or even accidents. This is not just a theoretical concern. The reality is that our technology, as advanced as it is, isn't perfect. Communication breakdowns, GPS inaccuracies, or even cyber threats can pose significant risks in a system that relies heavily on precision and inter-connectivity.
This is where my work comes into play. Recognizing these challenges, my thesis focuses on developing a resilient Autonomous Intersection Management (AIM) system. This system is designed to withstand technological imperfections and unforeseen circumstances. By employing advanced algorithms and reinforcement learning techniques, the AIM system can adapt and respond to various disruptions, ensuring that traffic continues to flow smoothly and safely, even when individual components fail or behave unpredictably.
What made you want to pursue a PhD?
I saw a chance to really dive into how self-driving cars and intelligent traffic systems could change our daily commutes. I was curious about making these technologies not just cool but also really reliable and safe, especially when things go wrong.
What is the most fascinating or interesting with your thesis subject?
This research is not only fascinating due to its innovative use of cutting-edge technology but also because of its significant real-world implications. By prioritizing safety, reliability, and efficiency, my work attempts to address key challenges in autonomous vehicular network, offering solutions that could impact future urban mobility and smart city infrastructure.
Do you believe some results from your research will be applied in practice eventually? And if so, how / how?
Absolutely, my research on improving traffic management has a strong chance of being applied in the real world. It might not mean my system gets used exactly as it is, but I'm pretty excited about how it brings new ways of thinking, analyzing, and improving traffic systems to the table. Think of it getting into smart city projects, influencing how self-driving cars are controlled. My research could be a big deal in making our streets smarter and safer.
What are your plans?
As my interest in the field, which already from the start was high, has increased further, I would like to continue in the field. I wish to get involved in future projects that aim to make vehicles as well as roads safe at the same time as the traffic flow is efficient.
Länk till artikeln Zahra Chamideh improved self-driving cars.
Robin Atle studied memristors
Publicerad: 2024-02-28
Title of thesis: Ferroelectric Memristors ? Materials, Interfaces and Applications. Link to thesis in Lund University Research Portal.
Defence: Friday March 8th, 09:15, room E:1406. Zoom link. Zoom ID: 63504410836
Describe your research in...
Title of thesis: Ferroelectric Memristors ? Materials, Interfaces and Applications.
Link to thesis in Lund University Research Portal.
Defence: Friday March 8th, 09:15, room E:1406.
Zoom link. Zoom ID: 63504410836
Describe your research in a popular science way
Today?s society is heavily dependent on electronics, from the smartphone in your pocket to the heat pump heating your house. This digitalization is the engineering result of ?chips?, where billions of electrical switches called transistors are integrated on an area the size of a fingernail. The huge improvements seen over the last 50 years can mainly be attributed to making these switches smaller, allowing one to pack more of them onto the same chip. However, we are now at a crossroads where this is no longer possible. Issues with heat dissipation and fundamental physical properties severely hamper today?s chips. This, coupled with an ever-increasing demand for computation driven by applications such as AI, requires new approaches which look beyond this miniaturization trend. By integrating new materials with superior properties and taking inspiration from the biological brain more energy efficient and faster systems can be achieved.
What made you want to pursue a PhD?
I had a taste of conducting research during my master?s thesis where I initiated the work on ferroelectric materials which at the end extended into a PhD project. I was intrigued by the process of research and breaking new ground which potentially could advance our society.
What is the most fascinating or interesting with your thesis subject?
The complexity and intricacies of modern chips which make up the backbone of all our electronic devices and applications is incredibly difficult to grasp. The ability to successfully integrate billions (!) of transistors onto a chip the size of a fingernail requires atomic scale accuracy, which in my opinion is probably the greatest engineering feat to date of humankind.
What are your plans?
For the coming months I will continue our research on ferroelectrics as there is much more to be done, then we will see what the future might hold!
Länk till artikeln Robin Atle studied memristors