| 摘要 |
<p>An antenna suitable for mounting upon vehicles, vessels or aircraft for communication via satellites comprises a conductive ground plane (18; 124) and a radiator element in the form of a conductor (20; 120) helically wound to define a frusto-conical shape with the ground plane (18; 124) as its base. The conductor may be formed upon a dielectric substrate (16; 118) in the shape of a truncated cone. The dimensions of the antenna element are selected so that the pitch angle (α) of the radiator element varies between a minimum (αMIN) of about 6 degrees and a maximum (αMAX) of about 8 degrees. The required pitch angle (α) may be achieved when the cone angle (ζ) of the frusto-conical shape is between about 5 degrees and about 20 degrees and the mean diameter of the frusto-conical shape is between about 0.3 and about 0.47 of a mean operational wavelength (1) predetermined for the antenna. The length of the radiator element (20; 120) is selected to be the minimum needed to sustain a wave. Optimum performance with compact size is attained when the ground plane is about two thirds of the operational wavelength, the cone angle is about 10 degrees and the maximum diameter of the frusto-conical shape is equal to about one half of the wavelength.</p> |
