| 摘要 |
Antenna systems particularly suited for reception of GPS satellite signals include a vertical stack of element arrays. Each array, which may comprise four dipoles positioned around a central axis, receives signals phased to produce a circularly polarized 360 degree progressive phase radiation pattern around the axis. By rotating in azimuth the radiation patterns of certain of the element arrays and controlling the amplitude of signals applied to different arrays in the stack of arrays, a circularly polarized radiation pattern can be provided encompassing the entire upper hemisphere above the horizon, with a sharp pattern cutoff at or slightly below the horizon. A seven array stack of individual arrays each including four angled dipoles, with a distribution network for providing signals of desired relative phase and relative amplitude to each of the 28 included dipoles, is described. GPS antenna systems can be provided in lightweight three inch diameter by 40 inch length cylindrical form, for example, for use in land surveying applications, as well as for use in aircraft approach and landing systems and other applications. For use on moving motor vehicles, antenna systems can be provided in a configuration about ten inches high including only three element arrays and having a reduced cutoff characteristic so as to accommodate antenna tilting during use.
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