Public defence in Micro- and Nanoelectronic Circuit Design, M.Sc.(Tech.) Mika Pulkkinen

The title of the thesis: Outlooks on Radio Transmitter Energy Efficiency and Ultra-Low Power Radio Transmitters

Doctoral student: Mika Pulkkinen
Opponent: Dr HDR Andreia Cathelin, STMicroelectronics, France
Custos: Prof. Kari Halonen, Aalto University School of Electrical Engineering, Department of Electronics and Nanoengineering

Wireless electronic devices have become a part of the everyday life. Such devices often use a radio transmitter, a radio receiver or both for exchanging digital data wirelessly with other devices. Examples of the present-day radio-equipped wireless devices are mobile phones, wireless earbuds, remote control car keys and wireless sensors. Also many other types of wireless devices are currently in use and even more such devices have been envisioned, for instance, related to the Internet of Things. 

The wireless devices suffer from a widely known problem: they are generally powered by a battery or a rechargeable battery and, eventually, the energy runs out, the device stops operating and the battery needs to be replaced or recharged. It is generally desirable to reduce the rate of occurrence of such stops. This can be achieved, for example, by reducing the power consumption of the device. In the radio-equipped devices, a major share of the power may be consumed by the radio circuits. Thus, research has been ongoing to find new transmitter and receiver solutions that consume ultra-low power. 

This thesis contributes to the study of ultra-low power integrated radio transmitter circuits. One of the goals in this work has been to find transmitter solutions that achieve improved energy efficiency compared to earlier works. This work presents insights on the energy efficiency of transmitters, discusses how the energy efficiency is impacted by the utilized modulation scheme and presents new integrated transmitter circuits. One of the presented new transmitter designs consumes less than 50 microwatts of power during continuous data transmission and, nonetheless, it enables a line-of-sight uplink range of one kilometer even without use of highly directional antennas. A comparison with a wide range of other ultra-low power transmitters shows that this transmitter is state of the art in terms of energy efficiency. 

The presented discussion and research results could help in the design of more energy-efficient transmitters. Achieving improved energy efficiency could help to improve the operating times of future wireless devices and, particularly, wireless sensors. 

In addition to the transmitter discussion, gesture sensor interfaces are presented that consume less than four microwatts of power. They enable detection of simple gestures over a short distance and could be used as human interface devices in ultra-low power wireless or other devices.

Keywords: RF, radio, transmitter, energy efficiency, low-power, gesture sensor

Thesis available for public display 10 days prior to the defence at: https://aaltodoc.aalto.fi/doc_public/eonly/riiputus/

Contact information:

Doctoral theses in the School of Electrical Engineering: https://aaltodoc.aalto.fi/handle/123456789/53