| 摘要 |
<p>An antenna configuration capable of providing either shaped conical or uniform hemispheric coverage to circularly polarized signals from a very thin or flush mounted radiation structure. For this purpose, the antenna is configured of an array of (N = three or more) radiation elements (11-14) fed in phase rotation (i.e. 360 /N phase difference between elements) to provide circular polarization. These elements may be short asymmetrically top loaded stubs, unbalanced slots, "L" type stubs, "U" shaped slots or other types of unbalanced elements which provide null free coverage in a hemisphere. The shape of these elements and their position in the array control the desired shaping of the antenna pattern. The antenna elements are provided on a first printed circuit board (15) that is spaced apart by a thin dielectric spacer (20) from an impedance matching/phasing network such as from 90 and 180 hybrid networks formed on a second printed circuit board (21). The ratio of zenith (or nadir) to horizon signal is controlled by the location of vertical feed wires that extend from the hybrid-containing circuit board through the spacer to the radiation elements, and the degree of unbalance of the radiation elements themselves. Assembly of the components of each antenna structure is accomplished by mounting screws that extend from one printed circuit board through the thin dielectric spacer to the other board. The resulting thin structure permits conformal mounting to curved surfaces such as an aircraft fuselage; if desired, however, the antenna may be mounted in a recess below the surface of the aircraft to thereby provide a completely flush mounting arrangement. </p> |
