有限接地板对圆形微带天线辐射特性的影响

The Effect of Finite Ground Plane on Circular-Disc Antenna Radiation

本文探讨有限接地板及其边缘劈形状对圆形微带天线辐射特性的影响。文中用接地板边缘绕射场与微带天线直接辐射场相对相位合成的方法改善圆形微带天线前向辐射特性的计算精度和计算其后向辐射方向图。微带天线直接辐射场用磁壁围成的腔体模型进行计算;边缘绕射场的计算,在E面采用一致几何绕射理论(UTD),在H面,由于边缘一阶绕射场为0,本文引入斜率绕射计算前向辐射方向图,用等效流法计算E在整个接地板边缘产生的绕射对H面后向辐射方向图的贡献。算例表明,本文的计算结果与可资比较的实测曲线吻合一致,而文[1]E面前向辐射方向图的计算结果与实测曲线比较,最大误差高达5dB,证明本文方法提高了计算精度。本文给出了具有不同尺寸、形状和不同边缘劈角的接地板的圆形微带天线的辐射特性,得出了利用改变有限接地板的几何特性参数来控制微带天线辐射方向图的途径。

The effect of finite ground plane and its wedge shape on the circular-disc microstrip antenna radiation is considered. A method of superposing diffraction field of finite ground plane edge and direct radiations from the antenna element is presented to improve the calculation of forward radiation characteristics. The backlobes of antenna radiation are also calculated. In the paper, direct radiation fields of microstrip antenna are computed by means of the a cavity model formed by magnetic wall. The uniform geometrical theory of diffraction (UTD) is used for dealing with edge diffraction fields in E-plane. In H-plane,a slope diffraction coefficient is introduced for calculation of forward radiation patterns,because first order diffraction fields from edge are zero. Concerning the contribution of diffraction of Eθ at whole edge,the equivalent current technique is used for calculating the H-plane backward radiation patterns. It is shown that the method presented here is prior to that of Ref. [1]. The numerical results of this paper are in good agreement with the available measurment data,while the maximum difference of radiation patterns in E-plane between the rusults of [1] and the measurement data reaches 5dB. The radiation characteristics of disc microstrip antennas of different size,shape and wedge angle ground planes are given. The ways of controlling microstrip antenna radiation pattern by changing geometrical properties of finite ground plane are obtained.