| 摘要 |
A dielectrically loaded antenna comprises a first group of elongate antenna elements 10A - 10F extending over a dielectric core 12 to form closed-circuit terminations at a linking conductor 20U and a second group of elongate antenna elements 11A - 11D extend over the core 12 towards the linking conductor 20U to form open-circuit terminations spaced from the linking conductor 20U. The said elements may be helical elements connected to feed nodes 13K, 13L for dual band frequency operation. Alternatively, a dielectrically loaded antenna comprises elongate antenna elements forming open-circuit end arrangements where each of the said antenna elements has a length of (2n-1) λg/4, where λgis the guide wavelength at an operating frequency and n is an integer. Alternatively, a dielectrically loaded antenna comprises first and second groups of elongate antenna elements where the first group of elements are longer than those of the second group such that they provide different circularly polarised resonant frequencies which are arranged such that when the elements are formed into adjacent pairs sequentially in a particular direction around the core, the number of said pairs with a first group element preceding a second group element equals that with a second group element preceding a first group element. |
