| 摘要 |
An antenna comprises at least three linear conductor elements 5, 6, 7 arranged in a series. The middle element 6 is a first length and the elements 5, 7 on either side are a second length, which is different from that of the first length. Two feeding points 1 - 4 are located at the gaps between the middle and side elements. The phase of the signal provided at each feed point may be changed by 0{ to 180{. The number of gaps and feed points may be two or more. A signal power divider 22 may be used to supply the signals to the feed points 1 - 4. The antenna elements 5 - 7 may be formed by linear wires or plates or by printed elements on a circuit board which may include quarter wavelength balun elements 19, 20. Also disclosed is an antenna comprising at least two linked spiral conductor elements of the same length where there is a feed point at the centre of each spiral. The above antenna arrangements may provide compact dual band antennas which may be used in compact antenna array formations. The distance between feed points may be varied to match the feed impedance to an input impedance of between 35 L and 150 L . The number of feed points and their spacing and the feed signal phase may be adjusted to influence the frequency, gain and magnetic signal pattern radiated by the antenna. |
