Chenhao Chu, Sagar K. Dhar, Xinyu Zhou
©SHUTTERSTOCK/GAUDILAB
The 18th High-Efficiency Power Amplifier (HEPA) Student Design Competition (SDC) took place at the 2022 IEEE International Microwave Symposium (IMS), on 21 June 2022. The competition was held by the IEEE Microwave Theory and Technology Society (MTT-S) Microwave High-Power Techniques Committee (MTT-12) in collaboration with Keysight Technologies. This year’s event was held in person after two years of virtual competitions (the 16th and 17th HEPA SDCs) during the COVID-19 pandemic. IEEE Young Professionals (YPs) from all the around the world gathered in Denver, CO, USA, to participate in the competition and discuss their experience in the design of HEPAs.
In the HEPA SDC, the contestants were required to design and fabricate a highly power-efficient linear PA at a frequency of their choice between 1 and 10 GHz and take the PA to IMS2022. Performance measurements were made by highly skilled engineers from Keysight Technologies. The specific design requirements can be found in [1].
The HEPA SDC is open to all registered students, both undergraduates and graduates, at recognized educational institutions around the globe. There is no restriction on age. Participants must be full-time students during the time the work is performed. A signed statement from students’ advisors is needed to prove that the work is principally the effort of the participants. Prizes are provided to the top three winners, sponsored by Keysight Technologies, Modelithics, and Cadence [2].
Six teams entered the 18th HEPA SDC, and 11 PAs were successfully measured. The first-place winner was the team from Friedrich-Alexander-Universität Erlangen-Nürnberg, led by Alexander Deublein and Michael Loose and advised by Prof. Robert Weigel. The second-place winner was the team from the University of Central Florida, led by Jiachen Guo and Haifeng Lyu and advised by Prof. Kenle Chen. The third-place winner was the team from University College Dublin, led by Chenhao Chu and advised by Prof. Anding Zhu. The winners from three teams shared their experience during the HEPA SDC for MTT-S YPs.
My passion for electronics started relatively early in my teens. Through various projects, a study of communications engineering and a job as a design engineer in a small company, the desire for a more profound understanding became even stronger. Eventually, I found my way to a Ph.D. position in the field of new cellular base station PAs, where I came across the HEPA SDC.
Being someone who has previously approached development tasks with a more practical approach, I particularly appreciate real-life design requirements as a reason to delve theoretically deeper into projects. Mastering the conflict between linearity and efficiency to win the HEPA SDC is the central task of modern PA design. Together with my colleague Alexander, we progressed to a finished demonstrator of a Doherty PA, which incorporates much more than nonlinear RF design. We gained many new insights and exchanged knowledge that will be of great benefit for our further work (Figure 1).
Figure 1. Michael Loose (second from right) was introducing their PA board to the other MTT-S YPs.
Thanks to the support of the MTT-S, it was possible for both of us to attend IMS2022. The numerous lectures and, in particular, exchanges with peers gave me the feeling of being part of something great and having chosen the right field.
For me, the story of PA design actually began in 2021, when I stumbled across an open Ph.D. position focused on Doherty PAs. I quickly realized that this was a great opportunity to learn more about nonlinear RF circuits and really understand them. I got lucky and was offered the position after a few interviews, which gave me the opportunity to dive deep into PAs.
At that time, although I felt anything but naive, I was not aware of the challenges PA designers face on a daily basis and therefore also awaited me: the power and voltage handling capability of RF components and materials suddenly became an omnipresent issue. In addition, the conception of heat dissipation for the RF transistors superseded RF requirements as a central concern. Nevertheless, it has always been exciting to develop suitable solutions and better understand the gallium nitride high-electron mobility transistor devices that are used. The more I learned about PAs, the more my respect grew, regardless of the esthetic appearance of a PA circuit.
Since hands-on approaches are often an excellent way to quickly develop deep understanding, I was told during my interviews that participation in the HEPA SDC would be a great way to use such methods. Looking back, I fully agree, as the SDC asks participants to meet a fairly simple specification that nevertheless reflects the inherent PA tradeoff between linearity and efficiency.
However, completing the PA demonstrator for the HEPA SDC in time would not have been possible without the support of Michael, whose skills were a perfect counterpart. While my contributions were limited to the RF section, he designed the carrier block matching the PCB and custom low-power adjustable gate voltage drivers (Figure 2).
Figure 2. Alexander Deublein (middle, wearing a gray T-shirt) was tuning their PA board in the 18th HEPA-SDC.
Thanks to the financial support of the MTT-S Ph.D. Student Sponsorship Initiative, we were both able to travel to IMS2022, attend our first-ever international conference, and connect with scientific peers from all around the world. We are already looking forward to the next opportunity to continue the interesting conversations we had.
My story with the HEPA SDC began at IMS2019, where I had the chance to meet the knowledgeable judges and energetic and creative colleagues from all around the world. Their professionalism and encouragement have driven me to attend the SDC from then on. With our group members’ and advisor’s diligent and innovative work, we won the 2020 and 2021 HEPA SDCs, with a record-breaking score. The SDC is a part of my student career, giving me unforgettable memories for life (Figure 3).
Figure 3. Haifeng Lyu (seated right) was in the 18th HEPA-SDC with other MTT-S YPs.
My story with the HEPA SDC started in June 2020, when the world was struggling against COVID-19. Differing from other teams, I worked as the only team member for the competition. It was pretty challenging to start from scratch, but I got good guidance and strong support from my supervisor, Prof. Zhu. I also discussed the measurement setup for the two-tone signal test with other research peers. Moreover, I referred to the invited articles in IEEE Microwave Magazine from the first-place winners of previous HEPA SDCs.
My first submission, to the 16th HEPA SDC (held virtually and steamed online on 16 October 2020), was a failure because of delayed PA board fabrication and shipment. However, I acquired precious experience in Doherty PA design, two-tone signal tests, PA board fabrication and debugging, and the tradeoff among efficiency, linearity, output power, and bandwidth. Moreover, I learned how to make a suitable arrangement for competition preparation and utilize my Ph.D. research knowledge of PA designs. Indeed, I won three prizes in the following HEPA SDCs: second place at IMS2021, first place at Radio and Wireless Week (RWW) 2022, and third place at IMS2022.
I offer special thanks to the IEEE MTT-12 committee, Keysight experts, and judges for the successful organization of the competition. After the virtual competitions at IMS2021 and RWW 2022, I went to Denver to attend IMS2022 and participate in the HEPA SDC in person. It was an excellent opportunity to meet professors, friends, and SDC teams worldwide (Figure 4). I would like to encourage graduate students and YPs to participate in HEPA SDCs. “It has always been an exciting and unforgettable memory for me in my research and student life, and no doubt, it will be the same for you too!”
Figure 4. Chenhao Chu (middle) was in the 18th HEPA-SDC.
Congratulations again to the winners from the three teams. We hope their stories will inspire the MTT-S YPs to learn about HEPAs and participate in the HEPA SDC in the future. We are looking forward to seeing new generations of students at the 19th HEPA SDC, in San Diego, CA, USA, for IMS2023.
[1] “IMS2022 Student Design Competition,” Institute of Electrical and Electronics Engineers, Piscataway, NJ, USA, 2022. [Online] . Available: https://ims-ieee.org/SDC2022
[2] “High Efficiency Power Amplifier Student Design Competition 2021,” Institute of Electrical and Electronics Engineers, Piscataway, NJ, USA, 2021. [Online] . Available: https://mtt.org/hepa_student_design_competition_2021/
Digital Object Identifier 10.1109/MMM.2022.3226552