Research On The Parallel FDTD Algorithm And Its Applications On Novel Invisible Structures

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.