What is the topic of your dissertation?
My Dissertation is about the development of power amplifiers (PAs) at millimeter-wave and submillimeter-wave frequencies, concretely at frequencies between 200 and 330 GHz, using the 50 and 35 nm mHEMT technology that Fraunhofer IAF provides. Due to the operation at these high frequencies, the communication systems achieve a high degree of compactness, high transmission data rate and improved geometrical resolution in images. At these high frequencies the development of power amplifiers is a really high challenge, as the power density of the transistors is limited by the parasitics, and the losses of the passive elements used to connect the transistors together is also increased with the frequency.
»I analyzed and developed a new technique based on connecting transistors in series (stacked-FET configuration) , enhancing the bandwidth, gain and output power of the PAs.«
You are the third generation of Spanish researchers working in the microelectronics department at IAF. Before you, your doctoral supervisor and her doctoral supervisor, too, already came to IAF. What do you think about this strong link between Spanish universities and IAF?
When I applied to do the PhD at Fraunhofer IAF I did not know about this story. When I begun to work at Fraunhofer IAF the department leader told me about it. I think this shows a very strong and long-lasting collaboration of Fraunhofer IAF and PhD students who had been working there and then become professors. Fraunhofer IAF has extremely good equipment and very good resources to do research.
»The mixing between the two cultures with different ways of thinking can be also productive for the research and can give new results and also scientific publications of interest.«
What did you enjoy most about working here and being in the TALENTA program for female scientists?
I was employed in Fraunhofer IAF for the first two years through the Talenta program, which finances and provides courses for woman who want to do research in a Fraunhofer institute. This helps women to go into the research field and also to have more time to focus completely in the PhD, which is really advantageous in term of pursuing a scientific career.
»The work at Fraunhofer was a new and grateful experience for me. There are not many places in Europe where monolithic microwave integrated circuits (MMIC) at THz ranges can be fabricated, processed and measured. Fraunhofer IAF possesses an enormous clean room and the required measurement equipment to do this.«
On top of that, different technologies are available, so that different circuits can be tried out. Another advantage is the high flexibility of the research carried out, and the possibility of trying out different and novel aspects. There are no limitations in this sense. Also, the supervision done from the group leaders and the colleagues is extremely good, they have a lot of knowledge and they help you any time that they can. This helped me a lot during my PhD.
What was your personal highlight during the PhD?
I think that my highlight was when I decided the main topic of my PhD. At the beginning I was trying some power amplifier topologies and they were not getting improved results in relation to previously developed conventional power amplifiers . I thought it was going to be really difficult to get a PhD thesis out of it. After that, a colleague recommended me to try this stacked-FET topology that was already used and published, but at much lower frequencies - around 56 GHz. Although it looked difficult to achieve, I just tried it out and I liked the results and the idea.
»I think that for any PhD student it is difficult to find out the right topic, and when I found it, I felt much better and more confident about my research at Fraunhofer IAF.«
In fact, it turned out that after presenting the Idea at the EuMW conference in 2016 I received the student prize. I think that the other researcher liked this concept, too.