一、引言小天线的尺寸一般远比波长为小,对线形天线来说指的是电偶极子,或偶极分的一半,即单极子天线,它的高度仅为波长的十分之一或数十分之一。这类天线的方向图,在赤道面上无方向性,在子午面上为“8”字,变化很小。通常研究的是它的输入阻抗。电偶极子和单极小天线(如图1)的输入阻抗 Z_λ随 l/λ的变化,已为大众所熟悉,大致如图2所示,显然它们的等效 I. INTRODUCTION The size of a small antenna is generally much smaller than the wavelength. For a linear antenna it is an electric dipole, or half of a dipole, which is a monopole antenna whose height is only a fraction of the wavelength One or a few tenths. The pattern of this type of antenna is non-directional at the equatorial plane and is “8” on the meridional plane with little change. The usual research is its input impedance. It has become familiar to the general public that the input impedance Z_λ of an electric dipole and a single-pole small antenna (as shown in FIG. 1) varies with l / λ, as generally shown in FIG. 2, apparently their equivalent