近地半菱形天线地波场强的计算

Ground-Wave Calculation of the Half Rhombic Antenna above the Half-Space

针对平面镜像法不能准确计算近地复杂线天线地波场强的问题,提出将平面分层媒质的格林函数法和前苏联学者Fock地波留数级数计算模型相结合,并以近地半菱形天线为例来进行计算。首先,推导了半空间并矢格林函数的空域形式,并采用加强离散复镜像法对表达式中Sommerfeld积分进行计算验证,之后采用矩量法求解半菱形天线的电流;其次,给出了偶极子在球形表面的Fock留数级数波场模型,并把模式方程变换为微分方程进行求解,考虑到大气的指数型模型,采用等效地球半径对偶极子地波场进行计算并同ITU-R推荐的指数型地波计算软件GRWAVE的计算结果进行对比验证。最后,推导了地球表面任意方向偶极子的地波场计算表达式,并根据求取的半菱形天线电流对地波场进行计算。提供了一种近地复杂线天线地波场的求解思路。

It is not able to calculate the ground wave accurately for the antenna by the image method,a new method that combines the closed-form Green's function method in the stratified media and Fock's method of residue series for the smooth and electrically homogeneous earth is presented to calculate the ground-wave of the half rhombic antenna.Firstly,the spatical Green's functions are derived for the half space,and the enhanced discrete complex image method(E-DCIM) is used to evaluate the Sommerfeld integrals,then the current of the rhombic antenna is obtained by the method of the moments(MOM).Next,the electromagnetic field is calculated by transforming the mode equation into differential equation,then the results of the GRWAVE and Fock's residue series which adopts the equivalent earth radius are compared.At last,the expressions of the ground wave for arbitrary oriented dipole are derived,and the ground-wave of half rhombic antenna is calculated.A new idea is presented for the calculation of the ground-wave.