1、低通滤波器论文：小型化宽阻带低通滤波器的设计与研究【中文摘要】随着雷达技术和无线通信等无线电技术的飞速发展,微波射频电路与系统越来越受到广泛的重视。微波滤波器是其中的重要组成部分之一,其性能的优劣很大程度决定了系统的工作质量。各种功能的系统相继开发,使得微波频谱资源日趋紧张,频率间隔不断缩小,这就对滤波器提出了更高的要求。其中微带滤波器以其具有较高性能、尺寸小、设计周期短、易于集成、用光刻技术易于加工等优点得到广泛的应用。近年来,高性能基板材料的研发使微带滤波器可以应用在很大的频率范围,从而使微带滤波器成为最常用的滤波器类型。低通滤波器是滤波器的重要组成之一,其用在发射端前级或接收端的后级,用
2、于滤除不需要的高频段信号。低通滤波器的带外抑制是一个重要指标,目前的低通滤波器带外有很多寄生通带,这使接收信号中除了需要的低频信号外,还有其他频段的干扰信号。由于目前每个频段已相继开发应用,要求接收的信号频率纯净,低通滤波器就必须有高的带外抑制度和宽的抑制频带范围。本文通过对国内外相关文献的总结整理和分析,归纳了微带滤波器的作用和宽阻带滤波器的发展历程和特点,分类总结出具有代表性的展宽阻带技术成果,再对微带滤波器理论进行了简单的阐述。之后对高低阻抗低通滤波器进行了详细的研究,设计了一个截止频率为 2GHz 的低通滤波器,用三维电磁场仿真软件 ADS、HFSS 进行了仿真验证,结果显示所设计满足
3、了预期的性能指标,但是在通带附近的阻带出现了寄生通带。针对其寄生通带研究了缺地陷结构用于谐波抑制,设计了一个不对称哑铃型缺地陷结构,将其嵌入到高低阻抗低通滤波器中,抑制了寄生通带。仿真和测试结果显示在不改变通带特性的基础上,使 3.2-18GHz 频带范围的抑制度大于 30dB,达到了展宽阻带的作用。最后在高低阻抗低通滤波器的基础上,改变其形状,嵌入简单低通滤波器抑制带外谐波,加入准分形结构改善带内特性,再用传输线 T 型等效减小滤波器面积,最后得到一个高性能小型化宽阻带低通滤波器。仿真和测试结果表明在 0-2GHz 范围内,最大插入损耗为 0.3dB,带内波动为 0.25dB,带内反射系数
4、S11 小于-13dB；通带到阻带的过渡陡峭,在 2.8-18GHz范围内,抑制度达为 33dB 以上；面积从最初的 61.812.4mm2 改进到 32.626.9 mm2,大大缩小了滤波器的最大尺寸。【英文摘要】With the rapid development of radar technology and wireless communications, widespread attention has been given to microwave/RF circuits and systems. Among these circuits and system the microw
5、ave passive filter takes an important role, i.e. the performance of these circuits and systems mainly depend on the one of the filter. In addition, as the more and more wireless systems have been used, the frequency bands of different systems will become closer and closer, which gives some specific
6、requirements to the filter. Among various kinds of filters, the microstrip filter has become the most commonly used filter type in recent years. The reason mainly focuses on the follows:firstly it has many advantages such as small size, low cost, easy to be fabricated or integrated and with higher p
7、erformance etc. At the other hand as the the development of more high-performance microstrip substrate materials, this make it possible to further increase the application frequency and reduce the size. In a word the microstrip filter should be the good one to be chosen to satificate the specific re
8、quirements of different wireless systems. Based on above the microstrip filter will be chosen to study the low pass filter in this thesis.Lowpass filter is an important part of the filter family. It mainly used in the transmitter or receiver to filter out the unwanted high frequency signals. Among t
9、he parameters of the low pass filter the band rejection is an important one. Because there are frequently many parasite passbands in lots of present lowpass filters, which will cause the interference signals to get into the receiver system to decrease the performance of the system. Nowdays the frequ
10、ency spectrum of being most commonly used in wireless communication has been almost fully developed, if the receiver wants to obtain purer signal frequency, a lowpass filter with a high degree of suppression and wide band rejection should become necessary.In this thesis, firstly the technologies abo
11、ut broading stopband of lowpass filter have been summarized, which is based on the analysis of the relevant literatures and the theory of microstrip filter. Then a detail study on the high-low impedance lowpass filter has been carried out. After these, a lowpass filter with 2GHz cutoff frequency was
12、 designed, simulated and validated by use of the 3-D EM simulatorsADS and HFSS. the results showed good agreements between the main performances of the design and simulation. But unfortunately there appeared the spurious passband in the stopband near the passband. then the defected ground structure
13、was studied and used to suppress the hammonics of this structure, at last a defected ground structure with a asymmetrical dumbbell-shaped was designed and inserted into the filter to reject the spurious passband. The results of simulation and measurement showed that there is no change on the pass ba
14、nd characteristics.but the inhibition is greater than 30dB between 3.2-18GHz.It showed that the defected ground structure can broarden the stopband.Finally, a high-performance compact wide stopband low-pass filter based on the high-low impedance structure was simulated and fabricated, which applied
15、the following step/technologies:changing the structure; embedding a simple lowpass filter to suppress the harmonics; adding quasi-fractal structure to improve the in-band characteristics and reducing the filter area by use of the transmission line T-equivalent. The results of simulation and experime
16、nt showed that the maximum insertion loss, the fluctuations and the maximum S11 is 0.3dB,0.25dB and-13dB respectively in the frequency range of 0-2.0GHz and the degree of suppression is greater than 33dB in the frequency range of 2.8-18GHz; the area of the filter is changed from the initial 61.812.4
17、mm2 to 32.626.9 mm2 and the maximum size of this filter is effictively reduced.【关键词】低通滤波器 宽阻带 缺地陷 小型化【英文关键词】lowpass filter wide stopband defected ground structure miniaturization【目录】小型化宽阻带低通滤波器的设计与研究 摘要 6-7 Abstract 7-8 第 1 章 绪论 11-15 1.1 研究背景及意义 11-12 1.2 小型化宽阻带低通滤波器的发展历程及特点 12-13 1.3 本文的论文结构和主要工作介
18、绍 13-15 第 2 章 滤波器理论基础 15-27 2.1 滤波器的分类 15-17 2.2 滤波器的基本技术参数 17-18 2.3 特定滤波器的实现 18-24 2.3.1 低通滤波器原型 18-22 2.3.2 滤波器频率变换 22-24 2.4 滤波器的微带实现 24-26 2.4.1 开短路短线等效法 24-25 2.4.2 高低阻抗线等效法 25-26 2.5 本章小结 26-27 第 3 章 高低阻抗低通滤波器的设计与分析 27-40 3.1 引言 27-28 3.2 高低阻抗低通滤波器的基本结构与分析 28-30 3.2.1 基本结构 28 3.2.2 参量分析 28-30
19、 3.3 高低阻抗线低通滤波器设计 30-39 3.3.1 设计指标 30 3.3.2 参数确定 30-32 3.3.3 ADS 验证仿真 32-36 3.3.4 HFSS 仿真实现和基板尺寸的研讨 36-39 3.4 本章小结 39-40 第 4 章 缺地陷高低阻抗低通滤波器的设计 40-58 4.1 DGS 技术综述 40-41 4.2 常见DGS 模型简介 41-45 4.2.1 哑铃型 DGS 41-43 4.2.2 螺旋型 DGS 43 4.2.3 曲线分型 DGS 43-44 4.2.4 U 型和 V 型 DGS 44 4.2.5 其他形状 DGS 44-45 4.3 DGS 等效
20、电路 45-48 4.3.1 对称 DGS 等效电路 45-47 4.3.2 非对称 DGS 等效电路 47-48 4.4 新型 DGS 参数及性能分析 48-51 4.4.1 第一节尺寸对频率响应的影响 49 4.4.2 第二节尺寸对频率响应的影响 49-50 4.4.3 第三节尺寸对频率响应的影响 50 4.4.4 偏移 d 对频率响应的影响 50-51 4.5 DGS 宽阻带高低阻抗低通滤波器的设计、测试和分析 51-57 4.5.1 滤波器的优化设计 51-55 4.5.2 DGS 宽阻带低通滤波器的测试 55-56 4.5.3 利用 DGS 展宽滤波器阻带的探讨 56-57 4.6 本章小结 57-58 第 5 章 小型化宽阻带低通滤波器的设计 58-67 5.1 新型滤波器的初始设计 58-60 5.2 准分形结构滤波器设计 60-62 5.3 滤波器的优化设计 62-65 5.4 滤波器的加工与测试 65-66 5.5 本章小结 66-67 总结与展望 67-68 致谢 68-69 参考文献 69-74 攻读硕士学位期间发表的论文 74
