组合式非周期缺陷接地结构中FDTD应用研究

The Study of Combinatorial Non-periodic Defected Ground Structure Using FDTD

组合式非周期缺陷接地结构(CNPDGS)是从光子带隙结构发展而来的,它是在微波电路的金属接地平面上人为地蚀刻出非周期性的“缺陷”,改变接地电流的分布,从而改变传输线的频率特性。与光子带隙结构(PBG)一样,具有明显的禁带特性。文中利用时域有限差分法(FDTD)研究了由CNPDGS结构构成低通滤波器的频率特性,并在此基础上研制了带宽可调节的低通滤波器,测量结果与数值分析一致性很好,进一步验证了FDTD分析的正确性,CNPDGS低通滤波器的研制,为该类型滤波器的设计提供了依据。最后讨论了FDTD方法中完全匹配层(PML)对电路特性分析的影响,给出了电路特性随PML层数变化的曲线。这对FDTD法分析缺陷接地结构时PML的选取具有一定的参考价值。

The Combinatorial Non-periodic Defected Ground Structure (CNPDGS) is developed at the base of Photonic Bandgap (PBG). In the structures, the Non-Periodically Defected Units are etched on the ground metallic plane of the circuits. The ground current distribution may be changed, and the characteristics of the transmission lines can be influenced. The CNPDGS can prohibit the propagation of electromagnetic waves within a certain band of frequencies. In this paper, the frequency characteristics of low-pass filter formed by CNPDGS structure are analyzed using Finite-Difference Time-Domain (FDTD) method. Furthermore the low-pass filters with tunable pass-band are developed. The measured results are accord well with the numerical results. The results can be used to design this kind of novel filters. At last, the effects of Perfectly Matched Layer (PML) on the circuits' characteristics are analyzed, and the curves of characteristic varying with the number of PML are presented. The conclusions in this paper will be helpful for choosing of the number of PML in the FDTD method.