Faculty of Engineering, LTH

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Low energy transceivers for high performance and high frequency communications

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The chip in the middle of the picture, is 0.9 mm times 0.9 mm.

Every transceiver needs local frequency generation. The chip in the middle of the picture, is 0.9 mm times 0.9 mm. The chip contains a frequency generation circuit with good performance and a very low power consumption, intended for future cellular communication applications. As this design is still not a part of a complete transceiver integrated on a single chip, the chip interfaced during measurements using thin metal wires and special fine-pitched probes. Photo: Therese Forsberg

The number of cell phone subscriptions in the world already outnumber the people by a few hundred million. In the future, machines, appliances and medical implants, etc. are also expected to have their own subscriptions. In each of these billions of wirelessly connected devices there is at least one transceiver, an electrical circuit that converts the digital data inside the device into analogue, electromagnetic signals that are sent through the air. The Focus of Therese Forsberg’s research has been to improve these transceivers.

Note: The dissertation takes place in E:1406, Ole Römers väg 3, Lund the 13 December 9.15.

As the data rates increase, the air becomes congested by signals. One identified way to alleviate this is to shift the signals to increasingly higher frequencies. Millimeter-wave frequencies are the frequencies that have a wavelength in the air between 1 and 10 mm. This corresponds to a frequency of between 30 GHz and 300 GHz. Therese Forsberg’s research is about designing the last part before the antenna. We have asked some questions.

What is the challenge?
–Among the higher frequencies, future 5G and WiFi communication is planned at for instance around 30 GHz and around 60 GHz. However, moving to such high frequencies is not a simple task. It makes the transmission more lossy, and the circuits a lot more difficult to design. Additional requirements on the transceiver circuits are that they should be suitable for hand-held, battery-powered consumer electronics, says Therese Forsberg, PhD Student at the department of EIT, LTH, Lund University.  

–So, the circuits need to be small, cheap and have a low power consumption. To make them small and cheap, the circuits in my research are made on a tiny silicon chip using a technology called CMOS. To decrease the power consumption of the circuits while still meeting the same performance requirements, good design choices are needed. My research has been about finding new, efficient circuit designs for future communication standards on millimeter-wave frequencies, and it has led to several successful of high-performance, low-power circuits, she continues

What made you want to pursue a PhD?
– Before pursuing my PhD, I worked at Ericsson in Lund, designing and testing communication transceiver circuits made in CMOS technology – much like the ones that I have worked with during my time at LTH. The difference was that Ericsson at the time did not design transceivers operating above 5 GHz. Communication at frequencies higher than that was still mostly something that was explored at universities. I found the specific combination of physically small analog circuits and a high frequency of operation very interesting to explore. I anticipated challenging problems, but also the inevitable future of the industry. For this reason, I chose to come to LTH and do research on a topic that never ceases to amaze me, both for how much is known and for how much is yet not known.  

How will the results from your research be applied in practice eventually? 
–The telecom industry moves fast, and as the universities have presented good results, it is rapidly catching up and starting to develop products that use the new findings. The outcome of my research, and that of others in the same field, is expected to find its way into mass-market consumer products within just a few years. 

What are your plans?
– As I feel ready to be a part of the movement to make the research of my field reach end consumers, I will be joining Ericsson in January. There, I will work with the team that develops transceiver circuits for the future 5G cellular networks, in which communication at millimeter-wave frequencies plays a very important role. 

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