【作者】 张胜；

【导师】 李英；

【作者基本信息】 上海大学 ， 无线电物理， 2007， 博士

【摘要】 随着移动通信的飞速发展和微波电路的高度集成化，作为通信系统关键部件的滤波器也要求向高性能、小型化的方向发展。同时，随着电子计算机的不断升级，时域有限差分法(FDTD)正成为分析这类电磁问题的强有力工具。本文主要针对平面微波滤波器的小型化和高性能进行了较广泛的研究，结合基片集成波导、双模结构、分形结构等一些新技术，提出了几种新型的低通、带通、带阻滤波器。并用FDTD法对其中的低通微带滤波器做了分析研究。论文主要包括以下内容：首先，简述了FDTD方法的基本原理，在此基础上，重点研究了用FDTD计算微带电路的难点问题，如PML层的边界条件处理和传输特性计算等。相关FDTD计算理论是进行微带滤波器研究和分析的基础。后面微带低通滤波器的计算结果表明了本章计算理论的正确性。其次，详细研究了一种新型缺陷微带结构(DMS)的阻带特性以及其与缺陷地结构(DGS)的区别。根据电磁仿真结果和等效电路原理提取了相应的集总参数。DMS结构更容易和有源微波电路集成，同时避免了电磁波从接地板的辐射。设计了两种DMS结构的三极点低通滤波器并用FDTD算法分析了相关结果，在此基础上还设计了一种DMS结构的五极点低通滤波器。这三种DMS结构的低通滤波器均具有较好的高频阻带特性和低频通带特性。第三，在分析三角形和圆形双模贴片滤波器的基础上，将分形结构应用于双模微带贴片滤波器的设计中。分别设计了一类分形结构的三角形滤波器和一类分形结构的圆形滤波器。分形结构能够更好得激励简并模的耦合，改善通带特性。同时，两类滤波器的通带两侧均出现衰减极点，极大得提高了滤波器的频率选择性。分形结构还能降低滤波器原有的谐振频率，有利于滤波器的小型化。第四，介绍了基片集成波导的结构特点，研究了它的一些基本特性，如传播模式、与矩形波导的等效条件等。设计了一种单个腔体的基片集成波导双模带通滤波器。同时，通过使用凹型过渡和接地共面波导过渡两种转换方式，解决了基片集成波导与微带线的过渡问题。该滤波器的品质因数高、插入损耗小，拓宽了窄带滤波器的应用范围。最后，讨论了用于开发人工异向介质材料的重要组成单元——金属开口环(SRR)和互补口环谐振器(CSRR)，研究了它们的谐振特性及基于这两种结构的平面带阻滤波器。提出将互补开口环谐振器刻蚀在微带线的导带上，从而充分利用电场进行有效激励，降低了谐振器的谐振频率、拓宽了阻带带宽。同时根据电磁仿真结果和等效电路原理提取了互补开口环谐振器的集总电路参数。在此基础上设计了两种一维互补开口环谐振器带阻滤波器，这两种滤波器均具有较宽的带宽和较深的阻带特性。更多还原

【Abstract】 With the rapid development of mobile communications and the high integration of microwave circuits, microwave filter which act as the key elements of communication system, are demanded toward to high performances and small sizes. At the same time, the incessant upgrade of electronic computers, the finite-difference time-domain (FDTD) method is becoming a powerful tool for analyzing these electromagnetic problems. This paper does a lot of research work on miniaturization and high performance of microwave filters. By taking use of new technologies, such as substrate integrated waveguide (SIW), dual-mode structure, and fractal structure, etc., some kinds of novel filters, such as low-pass filters, band-pass filters and band-stop filters, are proposed. FDTD analysis of low-pass filters is studied. The dissertation is summarized as follows:Firstly, the principal theory of FDTD (finite-difference time-domain) is briefly discussed. And then the difficult questions that use FDTD to compute microstrip circuits are researched, such as the boundary conditions of PML and transmission characteristics. These theories are the foundations of studying and analyzing microstrip filters. The compute results of microstrip low-pass filters, which are proposed in the next chapter, indicate that the computing theories about microstrip circuits are correct.Secondly, fully analysis the stop-band characteristics of a microstrip structure (DMS) and the differences between DMS and defected grounded structure. The lumped circuit parameters are extracted from EM simulation and equivalent circuit theory. This structure can be easily integrated with other active circuits, and avoids the leakage through the ground plane. Two types of three-pole low-pass filters using DMS are proposed, and the FDTD is used to analysis the related results. Based on two types of three-pole filters, a type of five-pole low-pass filters is proposed. Three types of filters all have good stop-band characteristics in high frequencies and excellent pass-band characteristics in low frequencies.Thirdly, based on analysis of triangular and circular dual-mode patch filters, the fractal structures are applied in designing dual-mode microstrip patch filters. A class of fractal-shaped triangular filters and a class of fractal-shaped circular filters are proposed. The degenerate-modes can be well excited, which improves the pass-band characteristics. Two classes of filters all have attenuation poles at each side of pass-band, which efficiently improved the frequency selectivity. Fractal structure also can reduce the resonant frequency of initial filters, which making for the filter’s.Fourthly, the basic structure of substrate integrated waveguide (SIW) is introduced and some fundamental characteristics, such as transmission mode and the equivalent condition as rectangular waveguide, are researched. A single cavity SIW dual-mode band-pass filter is introduced. The transitions of SIW with microstrip are solved by using concave transition and grounded coplanar waveguide transition. This kind of filter has high quality factor and low insertion loss, which expands the applications of narrow-band filters.Finally, the split ring resonator (SRR) and complementary split ring resonator (CSRR) that act as fundamental composite units to make metamaterial are discussed. The resonant performance and the planar band-stop filters that based on SRR and CSRR are researched. The complementary split ring resonator (CSRR) which etched in conductor strip of microstrip line is proposed. The electric field is fully used to excite the CSRR, which can decreases the resonant frequency and widen the stop-band bandwidth. At the same time, the lumped circuit parameters are extracted from EM simulation and equivalent circuit theory. Based on this type CSRR, two 1-D CSRR band-stop filters are proposed, both filters all have wider bandwidth and deeper stop-band.更多还原