| 摘要 |
PURPOSE:To obtain an antenna with a low profile, high radiation efficiency and suitable for the use in a frequency band being an ultrashort wave band or over by providing vertically two straight rod antenna elements in parallel and constituting the antenna that a metallic disc is connected to the highest tip. CONSTITUTION:The two straight rod antenna elements 202, 203 shorter than lambda/4 are provided vertically at a prescribed interval S in parallel and the metallic disc 201 is connected thereto. An impedance Zin, when viewed from a feeding section 205, of the antenna becomes inductive as the S is decreased and becomes capacitive as the S is increased. When the ratio of wire diameters rho2/rho1 is increased, the real part of the Zin, i.e., the radiation resistance is increased. The locus of impedance is unchanged even if the height (h) or the diameter D is changed. Thus, the Zin at a required frequency is set to a prescribed value being nearly the resistive component only by selecting properly the diameter D, the height (h), the wire diameters rho1, rho2, and the interval S. |
