| 摘要 |
<p>An antenna element is described. It comprises a ground plane (1) and a conical support (2) of a dielectric that with its bottom portion is attached to the plane and supports first to fourth radiation means having the shape of helical wires (3-6) which are symmetrically arranged around and are carried by the support. The radiation means are attached to the ground plane at their exterior lower ends and for transmission they are provided with a microwave signal each at their upper interior portions through a coaxial cable (8, 9) each, so that two orthogonal, preferably circular polarizations are generated by the emitted radiation. The antenna element is particularly characterized by a distribution network (15) arranged to divide, for transmission, the incoming signal in four subsignals which are offset in phase in relation to each other, each one of which being provided to a corresponding one of said first to fourth radiation means (3-6), and that adaption means (14) are arranged to adapt the output impedance of the distribution network to the input impedance of the radiation means so that it is substantially independent of the actual microwave frequency used within a relatively wide frequency range.</p> |
