On Friday 23 March 2018, PhD studenet Nikolaj Peter Brunvoll Kammersgaard from Electromagnetic Systems sucessfully defended his PhD on Wireless Communication for Custom Hearing Instruments.
Examiner at defence were Professor Anja Skrivervik, École Polytechnique Fédéral de Lausanne EPFL,Associate Professor Anders J. Johansson, Lund University and Niels Skou from DTU Space.
Nikolaj's PhD project was focused on modern hearing instruments which have transformed from simple analog acoustic amplifiers to intelligent complex digital devices. One of the recent additions is connectivity. The hearing instruments should be capable of connecting to smart phones, watches and TVs. In this way, the hearing instruments can function as a wireless headset as well. The user can then easily receive phone calls, listen to music or watch TV with the sound streamed directly to the hearing instruments at a volume they control. Furthermore, the hearing instruments on opposite sides of the head should be capable of communicating with each other to improve the acoustic performance and directionality through the combined input from microphones on both devices.
To enable all of these benefits for the hearing instrument users the radio channel between the ears and to accessories needs to be understood. Likewise, suitable antenna designs needs to be found. The most challenging case is the custom hearing instruments made to fit in the individual user’s ear canal. This sets high size requirements and causes variance. The radio energy cannot propagate through the head, but creeps around the head at the surface. For devices in the ear canal, the path out of the ears and around the head is longer than for the devices behind the ears, which makes the connection between devices on opposite ears harder to achieve. Therefore, they are the focus of this work. In the thesis, a new theoretical description of the radio wave propagation on the body has been found. This has been utilized to construct a simple, but precise, model for the radio channel between the devices on opposite sides of the head. Several antenna designs have been found and general guidelines for future designs have been developed.
Supervisor from DTU was Associate Professor Kaj Bjarne Jakobsen. Nikolaj's research was made in cooperation with GN Hearing A/S supervised by Jesper Thaysen, PhD and Søren Helstrup Kvist, PhD.
The final version of the PhD thesis to downloaded here.