Small balance-fed helical dipole antenna system for handset

In order to reduce the effect of operator´s hand and head on the handset antenna performance, a small NMHDA (normal mode helical dipole antenna), which has balanced terminals and is fed by a balanced line, is introduced and its performance, when it is built in the handset unit, is analyzed both theoretically and experimentally. The handset body is modeled by a rectangular conducting plate (ground plane), on which the NMHDA is placed, and the current distributions on the ground plane are analyzed by the electromagnetic IE3D simulator. The results are compared with the case of the unbalanced system, where the antenna is fed by an unbalanced line. It has been observed by the calculation that the current flow on the ground plane is very little as compared with the unbalanced system. These results imply that the operator´s hand and head may affect very little on the handset antenna performance at the talk position. The radiation patterns are also analyzed