A broad-band miniature dielectric-loaded personal telephone antenna-with low SAR

This paper describes a novel antenna type suitable for mobile telephone applications. It is a backfire fed, dielectric-loaded twisted loop antenna, that is designed to minimise the fields that are incident on the user´s head. The dielectric loading of the antenna reduces the antenna size so that the electric dipoles are formed over a shorter distance, thereby further concentrating the fields into a region that is close to the antenna. The loop is twisted through 180 degrees to create a magnetic reversal half way up the vertical aspect of the antenna, thereby concentrating the magnetic fields into a small space. The region over which large eddy currents can be induced in the user´s face is very significantly reduced. For these reasons and also due to the storage of electric field in the dielectric core rather than in the space around the antenna the proposed structure has a particularly low SAR characteristic. Finally methods of multi-banding and multi-moding the antennas are discussed. Ultimately it might be possible to make antennas, which operate over two non-contiguous cellular telephone bands with linear polarisation and also as GPS antennas with right hand circular polarisation