| 摘要 |
<p>A first embodiment relates to a four-wire fractional winding helical antenna characterized in that the characteristics are improved, especially the applicable frequency range is extended and the drawbacks in manufacturing helical conductor patterns are removed by devising antenna shapes, for example, by connecting plural cylinders or circular rods having different diameters in multistage and by forming helical conductor pattern on a cylinder base or multistage cylinder base accurately and easily using photoetching technique. A second embodiment relates to a four-wire fractional winding helical antenna characterized in that a shielding plate is intervened between the four-wire fractional winding helical antenna element and a controlling circuit arranged thereunder. An electromagnetic wave absorbing layer is provided on the side of the shielding plate, surrounding the side surface of the antenna element. Since the shielding plate has an aluminum or copper base and a lamination layer of ferrite thereon, even if the antenna is installed on an aircraft the electromagnetic wave radiated from the antenna body is prevented from reflecting on the antenna base and the aircraft body. Thereby, the shape of the radiation pattern of the antenna can be made more ideal and the degradation of the directional characteristic of the antenna can be prevented.</p> |
