【作者】 高强；

【导师】 袁乃昌；

【作者基本信息】 国防科学技术大学 ， 电子科学与技术， 2006， 博士

【摘要】 本文主要对无源电磁周期性结构的特性进行了数值仿真,并研究了在隐身材料和微波天线方面中的应用。作为工作基础,首先建立了分析周期性结构的理论模型和数值仿真工具,研究对象为以微带基片为载体的周期性结构。利用Floquet定理,无限大周期结构可以简化为一个周期单元来计算。数值仿真方法采用周期格林函数与矩量法相结合,采用谱域导抗法得到微带结构的全三维并矢格林函数,并采用快速[Z]矩阵和[Y]矩阵插值技术来加速计算速度,遗传算法的引入可以优化周期性结构达到要求的指标。利用所建立的仿真工具,对两种无源周期型结构进行了计算,包括频率选择表面的谐振特性和光子晶体的带隙特性。各部分的主要研究内容为:(1)频率选择表面的周期单元考虑了各种几何结构,包括方形贴片、方形孔径、Eruselum振子、方形环、圆环、单分裂环、双环等,同时也考察了单元尺寸、微带介质和布阵方式等不同参数对谐振特性的影响,提出了一些新型的频率选择表面——紧凑的、加载的和分形频率选择表面。另外还研究了频率选择表面的级联和优化,以满足工程设计需求。(2)对光子晶体的带隙特性进行了研究,其中包括—维光子晶体、光子晶体传输系统和多维光子晶体等。其中重点研究了以高阻电磁表面结构为代表的光子晶体的电磁特性,给出了高阻电磁表面的等效媒质模型,并利用该模型比较深入地探讨了高阻电磁表面的表面波带隙形成机理。对周期性结构在隐身材料中的应用进行了初步研究。利用周期性结构的同相反射特性作为人工磁导体,代替传统的电损耗Salisbury屏的间隔层,降低了整体厚度,同时又保持电损耗的稳定性能,为吸波材料的发展提供了一个崭新的方向。研究了光子晶体在微波天线以及天线阵列中的应用。分别研究了高阻表面在微带天线和波导缝隙天线中的应用、光子晶体覆层在微带天线中的应用和人工磁导体在口径耦合微带天线中的应用,并在研究单元的基础上,还研究了高阻表面在波导缝隙天线阵列中的应用,包括16元单脊波导天线阵和4元非对称单脊波导天线阵。研究表明,光子晶体的引入可以有效地改善天线和天线阵列的特性,主要体现在可以提高天线主瓣增益、降低后向和侧向辐射电平上以及减小天线单元和天线阵列间的耦合。最后利用光子晶体的频率带隙抑制相控阵天线单元的互耦,改善了相控阵天线的宽角阻抗匹配,消除了相控阵天线的扫描盲点问题,从而改善天线的扫描特性。更多还原

【Abstract】 The research work presented in this dissertation covers both the numerical simulation of passive electromagnetic periodic structures (PEPSs) and their applications in stealth materials and microwave antennas.As the basic of the research work, theoretical model and numerical simulation method has been established for the study of PEPSs that are constructed in the microstrip structures. The infinite periodic structure is reduced to one single cell by applying Floquet theorem. The numerical simulations are performed using periodic Green’s functions plus method of moments (MOM) and the whole dimensional dyadic Green’s functions are obtained by using spectral domain immittance approach (SDI). The [Z] matrix and [Y] matrix interpolation can accelerate the computation, and genetic algorithms can optimize the periodic structures to the aims.Using the above simulation tools, two passive electromagnetic periodic structures have been analyzed, including the resonance of frequency selective surfaces (FSSs) and the bandgap characteristics of photonic crystals (PCs). The primary work is as follows:(1) In FSSs, periodic cells with various types of geometries have been studied, including square patch, square hole, Eruselum dipole, square loop, circular loop, single split ring, double ring, etc. The effect of the cells’ sizes, the microstrip parameters and the array lattice types on the resonance is studied and some new FSSs, such as compact FSSs, loaded FSSs and fractal FSSs, are provided. In addition, the cascading and the optimization of FSSs has been investigated for the designing aims.(2) The bandgap characteristics of PCs are studied, including one-dimension PCs, the PCs transmission line and multidimensional PCs, etc. As the representative of PCs, the electromagnetic characteristics of high impedance surface (HIS) have been given emphasis to. The effective medium model of HIS is investigated and used to explain the reason why HIS has frequency bandgaps.The applications of periodic structures in stealth materials have been studied. Because of the in-phase characteristics, the periodic structures can be used as artifical magnetic conductor (AMC) and substituted for the spacer of the traditional electric Salisbury screen in order to reduce the entire thickness and preserve the stability of the traditional electric Salisbury screen. This can provide a new direction for absorbing materials.The periodic structures have been applied in microwave antennas and antenna arrays. The HIS has been used in microstrip antennas and waveguide aperture antennas separately. The applications of the PCs covers in microstrip antennas and the AMC in an aperture coupled patch antenna have been studied too. Based on the researches of antenna elements, the applications of HIS in waveguide aperture antenna arrays are also investigated, including sixteen-element single ridged waveguide antenna array and four-element asymmetric ridged waveguide antenna array. The results show that the PCs can improve the characteristics of antennas and antenna arrays. The gain of main lobe has addition, the radiation levels of back/side lobes decrease and the mutual coupling between the antenna elements or arrays can be reduced. Lastly, the applications of the PCs’ frequency bandgaps in phased arrays to suppress the mutual coupling between the phased array elements have been discussed. The PCs can improve the scan characteristics of phased array through ameliorating the wide-angle impedance matching and eliminating the scan blindness.更多还原