| 摘要 |
<p>A broadband antenna 5, which is operable over a frequency range of f1 - f2, comprises a monopole radiating element 7 which is at least partly enclosed within a sleeve element 8. The sleeve element 8 has a length * litres *2 of substantially 0.26 times that of the wavelength at the high operating frequency f2 of the antenna and a diameter selected to provide impedance matching at the feed point 6 of the antenna. The monopole radiating element 7 may have a length * litres *1 substantially 0.26 times that of the wavelength at the low operating frequency f1. The diameter of the sleeve 8 may be in the range of 6 - 10 mm and the sleeve 8 and the monopole 7 elements may be separated by one or more dielectric elements one of which may be air. The antenna 5 may be flexible and may be arranged with the sleeve portion 8 within the casing of a communication device whilst part of the monopole element 7 projects from the sleeve 8 and said casing.</p> |
