| 摘要 |
<p>An antenna element comprises a housing (2) having a base (4) adapted for attachment to a vehicle windscreen. Antenna elements are provided on printed circuit boards (7a, 7b) and form a dipole, the elements defining an included angle (A) of approximately 140°. When mounted on the inside surface of a vehicle windscreen, an improved radiation pattern is exhibited compared with a planar antenna. A coaxial cable (13) having inner and outer conductors coupled to the boards (7a, 7b) at their apex is routed in spaced relation to the element (7a) connected to the inner conductor, in such a manner that currents tending to be induced in the outer conductor of the coaxial cable are cancelled as a result of the proximity of the cable (13) to the element (7a). This enables the coaxial cable to be matched to the impedance of the antenna without the need for a balun.</p> |
