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摘要随着无线通信技术的迅猛发展，作为无线通信系统中重要的无源器件，滤波器对系统性能有着越来越重要的作用，系统对滤波器的要求也越来越高，高性能、小型化、低损耗成为滤波器研究的趋势。64869
伴随着无线局域网（WLAN）技术的应用和发展，由于通信向着更高频段发展，面临着频谱资源日渐紧缺的情况，能够兼容目前出现的通信频段资源的各种双频和多频通信系统已然成为了无线通信发展的主要方向。对于可以同时工作在无线通信中两个频段的双频段微波滤波器，除了要求提供稳定的双频特性和较小尺寸外，还要有较低的带内插损和较好的阻带抑制特性，因此，对双频带通滤波器的研究具有重大作用和实用意义。为了实现滤波器的小型化，降低成本，使用双模谐振器构成的滤波器，由于每一个双模谐振器可以作为两个谐振回路，这样使用双模谐振器设计成的滤波器，谐振器数目可以缩减到一半，使滤波器结构紧凑、尺寸小的要求成为可能。微带双模滤波器具有易于集成、工艺成熟等优点而被广泛应用。
本论文首先对双频带通滤波器和贴片双模滤波器在国内外的研究现状进行了分析、归纳和总结，并在此基础上设计了一种工作于WLAN的贴片双模双频滤波器。设计原理是利用矩形对称结构的贴片构成的双模谐振器内的一对简并模，采用合适的微扰方式使简并模发生分离耦合而形成双带通的性能。并运用HFSS软件对结构不断优化，分析了优化过程及结果，并最终确定了滤波器的结构尺寸，得到了很好的结果。
毕业论文关键词 双频滤波器，双模谐振器，方形贴片，无线局域网，微扰
毕业设计说明书（论文）外文摘要
Title The Design and Analysis of Dual-band Dual-mode Bandpass Patch Filter for WLAN Applications
Abstract
With the rapid development of wireless communication technology, as one of the important passive components in the wireless communication system, the filters play vital roles. High requirements for the filter system have been proposed, such as high performance, miniaturization and low loss etc.
With the application and development of the wireless LAN technology, communication is developing towards higher frequency, and the frequency spectrum resource is in shortage. Dual-band and multi-band communication system that can be compatible with a variety of communication frequency of existing resources has become the main direction of future development of wireless communications. Dual-band microwave filter of two different bands of wireless communication can not only provide stable frequency characteristic and small size, but also have low insertion loss and high stopband rejection. In order to realize the miniaturization and reduce the cost we can use the filter with dual-mode resonator. A dual-mode resonator can be used as a two resonant circuit, which consists of a dual-mode resonator filter. The dual-mode resonator would reduce half of the number of resonators. In this way，the dual-mode resonator filter takes the features of more compact structure, and smaller size. Due to the easy integration and technical maturity of microstrip dual-mode filter, it has been widely used.
In this thesis, the current research of dual-band bandpass filters and dual-mode resonators around the world has been presented and analyzed firstly. A patch dual-mode dual-band filter is design for a WLAN in this paper, which is based on dual-mode resonator with the degenerate modes．The perturbations approach is used to separate the degenerate mode and couple to each other． Eventually, the structure size of the filter has been optimized, good simulation results from HFSS software has been obtained.
Keywords Dual-passband filters，Dual-Mode Resonators，Square-patch, WLAN, Perturbation theory