Risto Valkonen

Near-Field Control of Handset Antennas Based on Inverted-Top Wavetraps: Focus on Hearing-Aid Compatibility

In this letter, it is shown that inverted-top wavetraps, which are quarter-wavelength-long resonators, can be used to control the near-fields of a mobile terminal antenna. The local reduction of the near-fields is especially important for the operation of the hearing aid of the user. The reshaping of the near-fields may also enable reduced specific absorption rate (SAR) values.

Recent advances in coupling-based antenna structures for mobile terminals

This paper reviews different recent approaches taken towards the realisation of space-efficient antenna structures for mobile terminals without the use of traditional self-resonant antenna structures, but instead by coupling the RF power directly to the wavemodes of a regular-sized terminal chassis. Several realisations of possible coupling structures are presented. In order to re-use the same coupling structure for several desired radio systems, reconfigurable matching circuitries have to be designed and optimised, which is a challenge that is highlighted in this paper. Also, the effect that the users hands have on the impedance and radiation characteristics of a coupling-based DVB-H antenna structure is investigated. This knowledge can facilitate the optimal design of the mentioned tuneable matching circuitry for coping with the many possible usage scenarios.