Triplate-type planar antenna and its array

A new type of electromagnetically coupled planar antenna made of a shielded triplate transmission line is studied and its design method is investigated. To this end: (1) studies are made on the radiation characteristics of the present planar antenna which are important when it is used as an array element. It is found that this planar antenna is sufficiently available as a linearly and circularly polarized array element. (2) The radiation characteristics are studied theoretically and experimentally for the array made of linearly polarized planar antenna elements. It is proven that this type of antenna system can be a useful form for a new type of linearly polarized array. (3) A method of configuration is studied for a circularly polarized array made of this type of planar antenna element. An antenna system is realized which has a broadband characteristic with about 5 percent bandwidth for the axial ratio of less than 3 dB.