| 摘要 |
A dielectric-loaded antenna for circularly polarised radiation has a generally cylindrical solid dielectric body (16) with a relative dielectric constant greater than 5, upon which body is plated a conductive sleeve (24) encircling the body and a conductive end layer (26) which, together with the body, form an open-ended cavity substantially filled with the ceramic material of the body (16). The electrical length of the cavity rim (24R) is a whole number of guide wavelengths corresponding to the antenna operating frequency less than 5GHz. A rotating standing wave is excited around the cavity rim (24R) by a feeder structure including two helical conductor tracks (14A, 14B) on the cylindrical surface of the body (16) which are coupled between the cavity rim and a coaxial feeder (20, 22) passing axially through the body.
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