摘要
当接收天线位于目标散射场的近区时，不仅要考虑天线各方向上场相位的不同，而且应计入幅度不同带来的影响。本文结合一致性几何绕射理论（ＵＴＤ）和物理光学法（ＰＯ）对一曲面角模型的近区散射特性进行了分析，给出了近区条件下凹面散射场的修正计算公式，并且分析了强方向性波束照射下镜面反射线不能用ＵＴＤ计算的原因，指出了近区与远区散射特性的差别所在。理论计算值与实验数据比较的结果表明，这一方法对近区散射场特性的分析是行之有效的。
Near fields computations are becoming more and more important in recent years.It is often thought that in this case the scatterers are in the far zone of the radiated field. and the receiving antennas are in the near zone of the scattered fields. One can easily find that the conditions used here are obviously different from those of the usual case. Therefore, not only the phase but also the amplitude of the incident wave should be taken into account to calculate the scattered fields undet these conditions. As an effective high frequency technique, tile uniform geometric theory of diffraction (UTD) is often employed to deal with this kind of problems due to its simplicity in concept and algorithm. HOwever, in practical cases , the directivity patterns of the antennas are often very sharp rather than omnidirectional.Consequently, the distribution of induced currents over the lit region on the scatteTers can not be simply regarded as uniform, espeially in the direction of main lobe, i. e., the currents vary drastically rather than slowly. Thus UTD must be abandoned in the direction of main lobe since the prerequisites of UTD have been violated. Hence, the physicsl optics (PO) is adopted here to treat the situation. It must be noted that the integral encountered in PO can not be simplified by the principle of stationary phase either. As a contermeasure, the iUuminated region of the main lobe is chosen as the integral domain to reduce the smount of computation. On the other hand, the influence of the other part on the scatterers, where the incident wave doeal't vary draslically (i. e., the other rays which are not in the direction of the main lobe), can be taken into account by UTD as usual. Moreover, as an improvement, the formula for the near fields calculating Of concave surface scattering is also pro～ in the paper. At the end Of the Paper, the near field characteristics of a curVed wedge have been examined in detail by the novel hybrid method, and the difference between near and far field is also pointed
出处
《电波科学学报》
EI
CSCD
1995年第4期12-17,共6页
Chinese Journal of Radio Science
关键词
近区场
几何绕射理论
散射
Near field, Electromagnetic scattering, Uniform geometrical theory of diffraction
