| 摘要 |
<p>GPS reception on helicopters and ground vehicles may be subject to varying near- gioimd interference. A compact antenna includes vertically spaced arrays of radiating elements. The first array provides a basic reception pattern. The second array provides a pattern having a distinctive low elevation angle phase reversal, By combining signals for these patterns an antenna pattern with a low angle omnidirectional elevation null characteristic is provided to suppress near-ground interference. Prior to combining, signals from the second array may be modii?ed in amplitude or phase, or both, on a semi- permanent basis, or may be adaptively modified on an active basis, in order to adjust the null characteristic. Antennas and methods are described.</p> |
