PhD student in efficiency enhanced millimiter wave power amplifiers

Information about the research and the division
Mobile connectivity is one of the driving forces of our current society, allowing us to be connected anytime, anyplace. This cellular connectivity is currently maintained through 4G and 5G base stations that somehow need to be connected to the core fiber network that is colloquially known as “the internet”. These connections are either implemented as fiber optic links themselves or use point to point microwave links. Currently about 50% of the base stations worldwide are utilizing microwave links, and the total amount of these links is expected to grow dramatically. However, it is not possible to simply increase the number of links at the current frequency bands since these are occupied in most regions so higher millimiter wave (mmW) frequency bands like E- and D-band (71-86 GHz, 130-165 GHz) will need be utilized next. These bands currently lack efficient transmitters to utilize the wide available spectrum in an efficient manner for a sustainable communication solution.

One of the core elements of the transmitters in these systems is the power amplifier (PA) which boosts the microwave signal to the levels required to bridge a few 10s of kilometers for a high-bandwidth point-to-point link. The energy efficiency of the PA, i.e. how much RF power is produced for each Watt of dc power, is extremely important because it not only directly affects the power consumption of the radio frontend, but determines what kind of cooling solution is required, and how much space and power this solution will require e.g. for a fan, or extra space for a heatsink. For microwave amplifiers the more practical efficiency measure is the power added efficiency (PAE) that also takes the required input RF power into account.

In this research project you will research, design, and implement energy efficient PAs as Monolithic Microwave Integrated Circuits (MMICs) in a state-of-the-art 100nm GaAs process. To increase efficiency you will investigate supply-modulation (i.e. gate and drain voltages that change according to the envelope of the transmit signal) and will design, analyze, and characterize supply modulator circuits. You will use a combination of theory, custom simulation code and commercial circuit simulators to design your circuits. Once implemented by an external foundry, you will then measure your circuits using the world class measurement capabilities at MC2, learning state of the art measurement techniques but also develop your own methods.

The goal of your research is to enable millimeter wave (mmW) transmitters with higher power efficiencies than currently possible suitable for wideband high peak to average power signals such as QAM1024. Your research will investigate the bandwidth limitation of different supply modulation approaches and their feasibility for mmW circuits. The research results may thus have strong impact in the realization of future wireless systems for communication, sensor, and imaging applications.

The position is hosted by the Microwave Electronics Laboratory at MC2 where the PhD student will have access to commercial state-of-the art MMIC and IC foundry processes and world-class measurement infrastructure allowing for a successful completion of this research project. At the Microwave Electronics laboratory currently 5 students pursue their Ph.D. in a similar area, which plenty of opportunity to collaborate and learn from and with peers. The research project is conducted together with Ericsson Research and Gotmic AB, a small business specializing in mmW MMIC design, so you will have access to academic and industry experts throughout the project. You will also be an important part of a cross-disciplinary team of PhD students and senior researchers that perform research on future communication systems, ranging from component to system level.

Major responsibilities
Your major responsibilities as PhD student is to pursue your own doctoral studies, including both coursework and research. You are expected to develop your own scientific concepts and communicate the results of your research verbally and in writing. In addition, the position will normally include 20% departmental work, mostly teaching duties. 

Qualifications


To qualify as a PhD student, you must have a master's level degree corresponding to at least 240 higher education credits in a relevant field. A suitable background for this position is a Master of Science in Electrical Engineering, Communication Engineering, or Engineering Physics with specialization in microwave electronics. Further, experience from RF circuit design, high frequency and microwave measurements, and/or advanced signal processing are important merits.

Since communication of research results is a central part of the work, communicative skills in English (oral as well as in writing) are vital. Furthermore, it will also be expected that you can take on responsibility, take own initiatives and work independently when needed. At the same time it is important that you are good at working in teams. Finally, you need to be able to disseminate results and knowledge within existing and new networks. This includes academia, industry and society at large.

Contract terms
Full-time temporary employment. The position is limited to a maximum of 5 years.

We offer
Chalmers offers a cultivating and inspiring working environment in the coastal city of Gothenburg. 
Read more about working at Chalmers and our benefits for employees.

Chalmers aims to actively improve our gender balance. We work broadly with equality projects, for example the GENIE Initiative on gender equality for excellence. Equality and diversity are substantial foundations in all activities at Chalmers.

Application procedure
Read more and apply here. 

Application deadline: 2022-08-08

For questions, please contact:
Assistant Professor Gregor Lasser, Microwave Electronics Laboratory,
Email: gregor.lasser@chalmers.se,
Phone: +46-31-772 4635

Professor Christian Fager, Microwave Electronics Laboratory,
Email: christian.fager@chalmers.se,
Phone: +46-31-772 5047


*** Chalmers declines to consider all offers of further announcement publishing or other types of support for the recruiting process in connection with this position. ***