| 摘要 |
A dielectrically-loaded antenna for operation at frequencies in excess of 200 MHz includes an antenna element structure disposed on a high dielectric constant core 12, which element structure comprises a pair of laterally opposed groups 10AB, 10CD of helical antenna elements. Each group comprises first and second mutually adjacent elements, of different widths providing looped conductive paths on the antenna, formed by the first elements of each group and the second elements of each group respectively, which resonate at differing respective resonant frequencies to yield a relatively wide operating bandwidth. The helical elements of each group define, between them, part of an elongate channel 11AB, 11CD which has an overall electrical length in the region of n g /2 within the operating frequency band to provide isolation between the looped conductive paths. The major part of each such channel is located between the elements so as to minimise intrusion into other conducting parts of the antenna. |
