| 摘要 |
<p>An electromagnetic antenna (20, 30) that is compact and easy to manufacture includes a portion of a coaxial cable (24) having a first predetermined electrical length, the cable's outer conductor (22) being removed from the portion for forming an electromagnetic monopole (28), a parasitic element (30) including a conductor spirally wound around the dielectric material (26) of the portion, the parasitic element having a second predetermined electrical length, and an electrical ground plane (22) disposed in an electromagnetically cooperative relationship with the portion and the parasitic element. The parasitic element may be secured with an adhesive to the dielectric material of the portion, and the first predetermined length may be substantially one quarter of a first predetermined wavelength and the second predetermined length may be substantially one half of a second predetermined wavelength. In particular, the first predetermined length may be 9.4 centimeters and the second predetermined length may be 7.9 centimeters. Also, the electrical ground plane may be disposed substantially perpendicular to the portion and the parasitic element, and the pitch angle of the parasitic element windings may be varied for generating selected spatial patterns of electromagnetic field intensity and power density. Methods of making an electromagnetic antenna from a coaxial cable are also disclosed.</p> |
