| 摘要 |
<p>A rod antenna and antenna circuit are described which make use of negative feedback to reduce the Q of the antenna, but which also makes use of a different coil tapping arrangement to significantly reduce electric field susceptibility on the detected signal from the main coil as well as different biasing arrangements to reduce noise. More particularly, in some embodiments of the invention the main detector coil of the antenna has a centre tap that is AC grounded with signal taps then being taken from the opposite ends of the main coil, and being respectively fed to the inputs of a differential amplifier. The output of the differential amplifier is then fed to the magnetic circuit of the rod antenna via a second inductor winding that is magnetically coupled to the resonance circuit of the main antenna coil. The AC grounding of the centre of the main coil significantly reduces susceptibility of the coil to the electric field. In addition, in one embodiment plural such circuits may be provided, with the antenna and feedback coils magnetically coupled. By having each antenna coil tuned to a different frequency, a multi-band or wideband overall antenna may be obtained.</p> |
