Helmet installed antenna using a half-wavelength circular loop antenna

Recently, in a field of a construction work, the use of wireless communication network is increased for easy communication among workers. They use mostly radio handsets when using wireless communication network. At this time, safety and work efficiency could be not good by holding them with a one-hand. A radio handset within a helmet is effective in order to reduce this dangerous situation. If one of the important components which are antenna for a helmet with a radio handset is disclosed, it has damage according to the environment. Therefore, the antenna has to be inside of a helmet and easy to attach on it with a flat shape. Also a good communication condition has to be maintained by a proper position. Attaching a miniaturized planar antenna on the underside of a visor is proposed. It is a half wavelength circular loop antenna (CLA) with a voluntary frequency at 449MHz. And it is manufactured by printed type for mass production. The diameter, 200mm, has to be miniaturized for attaching it on a visor. Therefore, the antenna is miniaturized with a double meander line inside of a loop. And then characteristics of installing on a visor and human body are studied. We would like to explain the characteristics of the designed antennas.