The word radome is a contraction of radar and dome. The function of radomes is to protect antennas from atmospheric agents. Radomes are closed structures that protect the antennas from environmental factors such as wind, rain, ice, sand, and ultraviolet rays, among others. The radomes are passive structures that introduce return losses, and whose proper design would relax the requirement of complex front-end elements such as amplifiers. The radome consists mostly in a thin dielectric curved shape cover and sometimes needs to be tuned using metal inserts to cancel the capacitive performance of the dielectric. Radomes are in the near field region of the antennas and a full wave analysis of the antenna with the radome is the best approach to analyze its performance. A major numerical problem is the full wave modeling of a large radome-antenna-array system, as optimization of the radome parameters minimize return losses. In the present work, the finite difference time domain (FDTD) combined with a genetic algorithm is used to find the optimal radome for a large radome-antenna-array system. FDTD uses general curvilinear coordinates and sub-cell features as a thin dielectric slab approach and a thin wire approach. Both approximations are generally required if a problem of practical electrical size is to be solved using a manageable number of cells and time steps in FDTD inside a repetitive optimization loop. These approaches are used in the full wave analysis of a large array of crossed dipoles covered with a thin and cylindrical dielectric radome. The radome dielectric has a thickness of ~λ/10 at its central operating frequency. To reduce return loss a thin helical wire is introduced in the radome, whose diameter is ~0.0017λ and the spacing between each turn is ~0.3λ. The genetic algorithm was implemented to find the best parameters to minimize return losses. The inclusion of a helical wire reduces return losses by ~10 dB, however some minor changes of radiation pattern could distort the performance of the whole radome-array-antenna system. A further analysis shows that desired specifications of the system are preserved.

中文翻译：

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结合遗传算法设计和优化具有子单元和非正交FDTD网格的大型圆柱天线罩

radome这个词是radar和dome的缩写. 天线罩的功能是保护天线免受大气因素的影响。天线罩是封闭结构，可保护天线免受风、雨、冰、沙和紫外线等环境因素的影响。天线罩是会引入回波损耗的无源结构，其适当的设计将放宽对放大器等复杂前端元件的要求。天线罩主要由一个薄的电介质弯曲形状的盖子组成，有时需要使用金属插件进行调整以消除电介质的电容性能。天线罩位于天线的近场区域，对带有天线罩的天线进行全波分析是分析其性能的最佳方法。一个主要的数值问题是大型天线罩天线阵列系统的全波建模，因为天线罩参数的优化可以最大限度地减少回波损耗。在目前的工作中，有限差分时域 (FDTD) 结合遗传算法用于为大型天线罩天线阵列系统寻找最佳天线罩。FDTD 使用一般曲线坐标和子单元特征作为薄介质板方法和细线方法。如果要在重复优化循环内使用可管理数量的单元和 FDTD 中的时间步长来解决实际电气尺寸问题，则通常需要这两种近似。这些方法用于对覆盖有薄圆柱形电介质天线罩的大型交叉偶极子阵列进行全波分析。天线罩电介质在其中心工作频率下的厚度约为 λ/10。为了减少回波损耗，在天线罩中引入了细螺旋线，其直径为~0.0017λ，每匝之间的间距为~0.3λ。实施遗传算法以找到最佳参数以最小化回波损耗。包含螺旋线可将回波损耗降低约 10 dB，但是辐射方向图的一些微小变化可能会扭曲整个天线罩阵列天线系统的性能。进一步的分析表明，系统的所需规格得以保留。