New conformal antenna concepts for hand-held telephones with significantly reduced interaction with the user

The increasing use of mobile telephones, in particular of hand-held sets, which have their transceiving antennas in the vicinity of biological tissue (head and hand) has caused public concern about possible radiation hazards. The majority of commercial mobile telephones uses monopoles with omnidirectional radiation patterns. As a result of this unfavourable antenna concept, more than 40% of the radiated power is absorbed by the user when the antenna as customary is held close to the head. Therefore, other concepts like the planar-inverted F antenna (PIFA) or the radiation-coupled dual-L antenna (RCDLA) have been investigated and offer visible improvement of efficiency by mounting the antenna on that side of the transceiver which points away from the user's head. The disadvantage of these side- and backmounted antennas consists in the increased influence of the user's hand on input impedance and radiation pattern. To overcome these drawbacks, we propose a new conformal antenna concept with significantly reduced interaction with both the human head and hand. It is a double T-slot antenna which consists of two slots in the form of the letter 'T'. This concept makes use of the metallic case as a shielding structure in order to reduce the interaction with the user's head.