【作者】 刘立国；

【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， 2013， 博士

【摘要】 隐身技术是现代武器生存的基础，现在战争中隐身与反隐身对抗比重增加，对战争的胜负起着越来越重要的作用。研究目标的电磁散射特性是隐身技术发展的基石，同时新兴材料不断涌现，新机理的隐身结构不断出现，都对目标电磁散射特性的研究提出了更高的要求和挑战。本文重点对频率选择表面和人工复合材料等为基础的新型隐身结构进行系统的理论和实验研究。针对这些新型隐身结构体组成复杂且多为色散介质的特点，研究了相关的快速仿真和性能预估方法，选用时域有限差分法（FDTD）作为主要的理论预估方法，完成了FDTD的高效率并行计算程序开发，并实现了适用于色散介质仿真计算的等效环路有限差分算法。本文首先阐述了串行FDTD并行化的关键技术，并将其部署在天河1号超级计算机上。并行有限差分算法是求解电大目标的有力工具，它具有天然并行的优点，能够充分利用集群的计算资源。天河1号是世界上最快的计算机之一，它提供了强大的计算资源，充分利用其丰富计算资源能够求解电大尺寸问题。在测试中利用7200进程花费少于48小时解决的电磁问题在普通PC机上要花费几年甚至十几年的时间，而此时的并行效率高于80%。针对传统FDTD算法计算色散介质时的缺点，实现了一种新颖的等效环路有限差分算法(EC-FDTD)。这种算法借鉴传输线算法的思想，在Yee氏网格中引入等效集总元件，包括常规介质中的等效串联电感、等效并联电容和左手材料中的等效并联电感、等效串联电容等。这样的等效方式使其可以提供适用色散介质计算的收敛性条件，更加适合仿真计算频率选择表面和超材料等色散介质。为了提高其计算效率，研究了核内加速技术，这种技术理论上可达到最高4倍的加速，实际应用中得到2倍左右的加速效果。使用EC-FDTD算法进行了超材料吸波体结构的设计，通过单双环电阻加载技术实现超薄宽频带电磁波吸收功能，使其单环具有6GHz-14.5GHz、双环具有4.5-14.5GHz的超宽吸波频带。同时针对单双环电阻加载设计中的耗时缺点，提出了不需借助全波分析方法的等效电路解析分析方法，这种方法在设计的初期能够极大地节约人力和物力。通过电阻膜加载技术设计单层和双层的复杂吸波结构，这种结构能够实现更好的吸波效果。单层电阻膜加载结构可实现在频带4.5GHz-13.5GHz内的吸波效果，双层结构可实现3GHz-21GHz的超宽带电磁吸波。隐身天线罩对于实现天线的带外隐身有着重要作用，利用EC-FDTD算法设计了工作频率为1GHz，隐身频带在3GHz-9GHz的电阻加载型天线罩。首次提出了利用龙膜代替电阻膜，实现工作频率2GHz，吸波频带为4.5GHz-12.5GHz的新型隐身天线罩。对上述的新型吸波结构和隐身天线罩进行了样品加工，实验结果验证了这些新型隐身结构的性质。更多还原

【Abstract】 The technology of stealth is foundation of survival for modern weapons. Thecounterwork between stealth and anti-stealth has a much larger proportion in today’swar and plays a more important role in deciding the final. The research on scatteringcharacteristics of the targets is the foundation to develop the technology of stealth.Furthermore the developed stealth based on new mechanisms arise as new materials arebrought forward. All of them raise the higher requirements as well as are challenges forthe relevant research. The paper places great emphasis on the novel invisible structurescomprising of frequency selective surfaces (FSS) and metamaterials. Thefinite-difference time-domain method (FDTD) was adopted as the primary predictionmethod to give a fast design and evaluation of such structures with complex anddispersive characteristics. The parallel realization of FDTD and high parallel efficencyis focused, and the equivalent circuit FDTD is realized which is suitable to cope withthe dispersive materials.The key points for a parallel FDTD solver are reported and the solver is deployedon the Tianhe-1A supercomputer. The algorithm of parallel FDTD is a powerful tool forsolving large electrical objects for its parallel nature. The Tianhe-1A supercompuer isone of the fastest computers in the world at present, which can provide very highcomputational capability. By using parallel computations, we completed a calculationon7200processors in less than48hours, where a serial version would have taken overseveral decades. The parallel efficency is more than80%up to7200processors.A novel FDTD algorithm named Equivalent Circuit FDTD (EC-FDTD) is realizedto overcome the shortages of the ordinary FDTD, which introduces equivalent lumpedelements from transmission line theory into Yee cell. It includes lumped elements suchas series inductance and shunt capacitance in the right-handed materials, as well asshunt inductance and series capacitance in the left-handed materials. Due to itspromising physical meaning, it can provide the condition of stabilization for thedipersive materials and can be easily generalized to arbitrary dispersive materialsincluding frequency selective surfaces and metamaterials. The technology of StreamingSingle-instruction multiple-data (SIMD) Extensions(SSE) was proposed by Intel and iscurrently utilized in personal computers. SSE is a kind of parallel speedup technology inone core. The speedup can be achieved four times in principle without changinghardware. Combined with SSE, the EC-FDTD can be apparently accelerated. Twicespeedup is achieved in the tests of this paper.The algorithm of EC-FDTD is utilized to design the wideband metamaterialsabsorbers by employing the single square loops and double squre ones loaded with thelumped resistors. The former has an absorbent bandwidth from6GHz to14.5GHz while the later has the one from4.5GHz to14.5GHz. An equivalent circuit (EC) method forabsorbers design is proposed without using full-wave analysis, which can predict theperformance of the absorbers. The EC method can save much time. The resistivesurfaces are employed to design the absorbers by ultilizing the single construction andthe double one to achieve much better effect of absoring. The former one has theabsorbing bandwidth from4.5GHz to13.5GHz while the latter has the ultr-bandwidthfrom3GHz to21GHz.The invisible radome has a great impact on reducing the radar cross section of theantenna out of band. Such radome loaded with the lumped resistors is designed atoperating frequency to be1GHz with the absent bandwidth from3GHz to9GHz by thealgorithm. The llumar glass is firstly used to realize such invisible radome with thetransmission properties at2GHz and absorbent bandwidth from4.5GHz to12.5GHzsimultaneously. And then these prototypes are fabricated and measured. From thecomparative results, the properties of the novel structures for stealth are verified.更多还原