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摘要随着现代无线通信技术的发展，工作在多个频段的微波器件越来越多地使用在各种通信系统中。例如在无线局域网（WLAN）、全球移动通信系统（GSM）和全球定位系统（GPS）设备中，射频接收机必须同时收发多个频段的无线信号。作为射频系统的重要器件之一，微波双频带通滤波器对系统性能有着至关重要的作用。因此，开展微波双频带通滤波器的研究具有非常重要的意义。 目前，双频滤波器在整体尺寸较小的前提下，很难实现滤波器宽带或者超宽带的带宽需求。为了解决双频频滤波器带宽限制的问题，可以结合超宽带滤波器的设计方法，研究带宽更宽的双频滤波器。 本论文首先对双频带通滤波器和超宽带滤波器在国内外的研究现状进行了分析、总结和归纳，并对其进行了优缺点的比较；其次介绍了一种在超宽带滤波器中增加阻带来实现双频带通滤波器的方法。通过研究特性阻抗对多模谐振器的影响、平行耦合和叉指耦合结构的比较、几种阻带实现的方法来分析各个参数对滤波器特性的影响。提出用加载三个开路支节的多模谐振器，来实现适用于WLAN 网两个通带的双频宽带带通滤波器。由于对称多模谐振器有四个奇/偶模谐振频率，各通带的中心频率和带宽可以通过改变多模谐振器的特性阻抗得到控制。8955
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关键词 双通带宽带，滤波器，多模谐振器，叉指耦合，开路支节
Title WLAN dual-band bandpass filter design and analysis
Abstract
Modern wireless communication systems demand that radio frequency (RF)
devices can operate in multiple bands. As a key component of multiband
communication system, such as Wireless Local Area Network (WLAN), Global
System for Mobile Communications (GSM) and Global Position System (GPS),
microwave dual-band bandpass filter is essential to the performance of the
system.
However, it is not easy to realize dual-wideband bandpass filters in
miniature filter structures. In order to solve the problem, the design
method of UWB (Ultra-Wideband) combined with a dual-wideband bandpass
filter can be employed for such purpose.
In this thesis, the current research of dual-band bandpass filters and UWB
filters around the world has been presented, analyzed firstly. Different
methods to design dual-band bandpass and UWB filters have also been
compared with each other. Then, a way to realize dual-wideband bandpass
filter by inserting a stopband within a UWB filter is proposed. Based on
the characteristic impedance and comparison of parallel and interdigital
coupled lines, the analysis of different ways to realize stopband the
structures and resonance of the multi-mode resonator are studied. A novel
dual-wideband bandpass filter based on a symmetrical multi-mode resonator
with three open stubs is proposed for WLAN bands. Due to the four
even/odd-mode resonator frequencies of the symmetrical multi-mode
resonator, the bandwidth and the center frequency of each passband can be controlled easily by changing the characteristic impedance of the
multi-mode resonator.
Keywords dual-wideband, bandpass filter， multi-mode resonator(MMR),
interdigital coupler, open stubs 目录
1 绪论 1
1.1 课题研究的目的和意义 1
1.2 国内外研究历史和现状 2
1.2.1 双频滤波器的国内外研究现状 .. 2
1.2.2 超宽带滤波器的国内外研究现状 . 4
1.3 本文的主要工作和章节安排 . 5
2 滤波器的基本理论 7
2.1 概述 .. 7
2.2 滤波器的主要类型 . 7
2.3 滤波器的参数指标 . 8
2.4 滤波器的设计原理 . 9