| 摘要 |
In the antenna structure there are, for two frequency ranges, two antenna elements, of which the first is a cylindrical coil conductor (2) forming a helical antenna. It comprises, in the direction of its longitudinal axis, a first portion (2a) and a second portion (2b), and the second antenna element (3; 6) is connected to the cylindrical coil conductor by a fixed connection at a junction (2c) lying between the first and second portions. The second antenna element may for example be a conductive filament (5a), a conductive pattern (5) formed on the surface of an insulating plate (3) or a small-diameter helical antenna (6). The first operating frequency is dependent upon the combined electrical length of the portions of the first antenna element and the second operating frequency is dependent upon the combined electrical length of the lower part of the first antenna element and the second antenna element. The bandwidth of the operating frequencies is dependent upon the positioning of the junction in the first antenna element. <IMAGE> |
