| 摘要 |
An antenna system for a mobile telephone operates by radio channel between the mobile telephone (1) and at least one at a time of a group of satellites (2) revolving in polar orbit or quasi polar orbit around the earth. The antenna system includes a cone-shaped antenna (3) for transmission and reception with at least four equi-angularly spaced apart spiral strands. Radio frequency signal is fed to or from the strands at the apex or small diameter end of the cone with relative phases to selectively produce for circularly polarized radiation, in a first mode of operation (m1), an antenna pattern of substantially hemispherical form, and in a second mode of operation (m2), an antenna pattern of substantially toriodal form. A switch mode function (SWF) block (11) is controlled by a control block (16) to automatically effect selection of the mode of operation in accordance with a priori or a posteriori selection criteria. These criteria may be communication mode responsive, telephone orientation responsive, or test and connection responsive.
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