Peak Internal Fields in Direct-Coupled-Cavity Filters

Microwave filters are limited in their power-handling capacity by high fields generated inside the filter. Simple formulas are derived here for the peak fields inside each cavity of a direct-coupled-cavity filter at any frequency. The computed peak fields in each cavity of a three-cavity, a four-cavity, and a six-cavity filter as a function of frequency are reproduced up to several harmonics. Inside the pass band, the internal fields are generally minimum at center frequency, rising to sharp peaks just outside the pass band. Phase characteristics were also computed, and their relation to the internal field amplitudes is explained.     

New Theory and Design for Hairpin-Line Filters

Hairpin-line and hybrid hairpin-line/half-wave parallel-coupled-line filters are preferred filters for microstrip and TEM printed-circuit realizations. This class of filters offers small size and, in general, needs no ground connections for resonators. A new design theory is presented that is based on a sparse capacitance matrix for the array of coupled lines that constitute the filter, as opposed to a sparse-inductance-matrix assumption in previous theories that is much harder to satisfy. It is shown that to a good approximation, hairpin-line filters result from frequency-scaling half-wave parallel-coupled-line filters. Because of this; the bandwidth can be accurately predicted. Design procedures are given for Type-A filters, which are useful up to 20-percent bandwidth. A variety of hybrid hairpin-line/half-wave parallel-coupled-line filters is possible, and their design is explained. Numerical results for a number of designs and experimental results for a 5-percent bandwidth filter are included.     

体声波滤波器理论及仿真

基于微加工技术制造的体声波滤波器品质因子高达数千,其性能已超过表面波滤波器,且可通过标准集成电路技术生产,将其用来替代通信系统中的传统射频滤波器,极具性能和价格优势。因此,该文以T型电路结构为基础,以固有衰减为出发点,推导体声波滤波器的通带和阻带频率特性。并以中心频率2.4 GHz、带宽36 MHz的体声波滤波器为例,作了详尽的分析和说明,并用Matlab软件仿真了其阻抗特性和传输特性。     

Theory and Design of Low-Insertion Loss Fin-Line Filters

A design theory is described for low-insertion loss fin-line filters that includes both higher order mode propagation and finite thickness of the dielectric substrate and the metallic fins. Design data for three-resonator type fin-line filters with several substrate thicknesses are given for midband frequencies of about 15, 34, and 66 GHz. The measured insertion losses in the passband are 0.25, 0.5, and 1.3 dB, respectively, for these three frequencies.     

广义中值滤波理论及其性质的研究

本文以传统的中值滤波为背景，给出了一种广义中值滤波（ＧＭＦ）的定义，并在此基础上，研究了有关数学模型、性质和基本定理。其效果不仅完善了中值类非线性滤波理论，而且还展示出一些有实用价值的新结构和新应用。     

用超模理论分析光栅耦合器型滤波器的特性

从实际测量的耦合器的形状出发,运用耦合的超模理论分析了在普通2×2光纤耦合器的熔锥区写入光栅制作滤波器的特性,并对不同类型的耦合器进行了比较。研究表明,即使在普通的耦合器上写入布拉格光栅,同样可以获得波长选择滤波器,并且存在最佳光栅位置和光栅长度。同时提出了获得窄线宽、边带抑制的滤波器的新方法,即在熔锥区写入非线性啁啾光栅。     

General Theory and Design of Optimum Quarter-Wave TEM Filters

The exact synthesis and design of a broad class of quarter-wave TEM mode filters is presented in a three-step procedure. The theory is applicable to all microwave filter forms consisting entirely of a cascade of quarter-wave lines, quarter-wave stubs, and coupled quarter-wave lines. The exact design of many conventional filter forms that heretofore could only be designed using approximate methods is possible using the techniques and functions described. General approximating functions that give the "best" transmission response in a Butterworth or Chebyshev sense are derived. The use of a maximum number of available singularities to augment the filter skirt response leads to a minimum element filter termed "optimum multiple." An optimum multipole design insures the "best" possible response for the minimum element and all corresponding redundant element networks. The designer has the freedom of introducing sufficient redundancy to obtain a design that is practical to construct, but which still realizes the optimum response. Judicious choice of network form often results in improved performance and reduced size in comparison with many conventional filter forms. Design procedures are presented that allow the practical realization of distributed filter networks in the form of quarter-wave lines. A design example and experimental results are given to confirm the theory.     

串行谐振滤波器调试中参数的提取理论

介绍一种提取串行耦合滤波器的各个谐振腔的谐振频率和相互谐振腔之间耦合系数的方法.利用终端短路网络的反射系数的相位来综合各个谐振腔的耦合谐振频率和相互谐振腔之间耦合系数.     

Application of Representation Theory to Dual-Mode Microwave Bandpass Filters

This paper discusses the physics behind the operation of dual-mode bandpass filters from a field theoretical point of view. It is argued that the two degenerate modes of the empty dual-mode cavity, commonly taken as the vertical and horizontal polarizations, become nonphysical when coupling and tuning elements are inserted. Instead, the original degenerate modes are rotated, or modified in a complex way, to generate two new modes whose characteristics depend on the coupling and tuning elements. It is shown that the tuning elements, as placed in existing dual-mode filter designs, act as both tuning and coupling elements. A working dual-mode filter can be designed with only “tuning” elements present. A physical representation of dual-mode filters in terms of the eigenresonances of the dual-mode cavities, with the tuning and coupling elements present, is introduced. Two fourth-order dual-mode rectangular cavity filters with the same response in the passband and its vicinity are also presented to demonstrate the similar role played by “tuning” and coupling elements in dual-mode cavities. The first filter uses only “tuning” elements, while the second is based only on “coupling” elements.      

Theory of Simulated-Skin-Effect Filters a Thin Film Approach to EMI

The theory of a new, ceramic lowpass filter, highly effective at very high frequencies, is discussed. Its excellent performance is based on simulation of the skin effect whereby the VHF, UHF and microwave currents are forced along a thin, electrically permeable resistive film deposited inside a high-? dielectric tube while a large dc current may flow through the coaxial conductor. Theory and experiment are in excellent agreement. In several respects these filters are better than cascaded filters (ferrites and dielectrics combined) which were, thus far, considered the best available. The simulated-skin-effect filter shows great promise of becoming a significant means in combatting conducted electromagnetic interference.     

Exact Theory of Interdigital Band-Pass Filters and Related Coupled Band-Pass Structures

An exact theory of interdigital line networks and related coupled structures is presented. The theory of parallel-coupled line arrays is reviewed briefly, and the derivation of exact equivalent circuits from the impedance matrix using modem network synthesis techniques is discussed. A simplified theory of equivalent coupled structures is introduced in order to avoid the lengthy analysis required when using the impedance matrix approach. Equivalent networks for the interdigital line are obtained by inspection, using a transformed capacitance matrix associated with the two-dimensional geometry of the conductors and ground planes. The techniques presented are simple to apply and allow a given transmission response to be obtained in a variety of line configurations. A practical design example and experimental results are given to illustrate the simplicity of the approach, along with general criteria for the design of practical filter networks with optimum transmission characteristics. The paper is directed toward the design of interdigital band-pass filters; however, the techniques presented can be used to analyze and design a much broader class of microwave networks. The relationship of the exact theory to existing approximate theory is discussed.     

基于一维光子晶体理论的平顶偏振滤波器设计

基于一维光子晶体理论,提出了一种级联薄膜玻璃腔结构的平顶偏振滤波器。给出了具体的设计实例,透射窗口处P偏振光的透射率的最小值大于99.6%,S偏振光的透射率最大在0.1%左右,且P偏振光的各透射窗口的中心频率符合国际电信联盟(ITU)标准。在此基础上,系统研究了该结构各介质膜层参数(包括固体介质腔)以及入射角对透射谱性能,如矩形度、占空比和频率间隔等的影响。该滤波器不但结构简单,易于实现,且在高透射P偏振光的同时能很好地截止S偏振光,在波分复用系统中有一定的应用价值。     

滤波器和信号滤波器

滤波器用于选择某一频带中的信号,分为低通(通过低频)、高频(通过高频频带)、带能(仅通过某一频带)和带阻(抑制某一频带)滤波器几种。滤波器频响特性的常用曲线表示衰减对频率的关系,衰减以分贝(dB)为单位,画在线性     

有源与无源滤波器教学中的对比分析方法

笔者在有源滤流器教学中，放弃了一般教科书常用的分析模式，尝试了一种新方法；即有源滤波器与无源滤波器对比分析的方法，并利用等效电路及相应的传输函数，重点突出了滤波网络中的“源”，清楚地验证了引入“源”以后的滤波器其Q值是大于无源滤波器的。     

Pascal Filters

We introduce a new type of filter approximation method and call it the Pascal filter, which we construct from the Pascal polynomials. The roll-off characteristics of the Pascal, Butterworth, and the Chebyshev filters are compared.      

Theory and Design of Linear-Phase Minimax FIR Filters with Mixed Constraints in the Frequency Domain

The alternation theorem is the core of efficient approximation algorithms for the minimax design of finite-impulse response (FIR) filters. In this paper, an extended alternation theorem with additional mixed constraints, i.e., equality-and-inequality constraints, is obtained. Then, an efficient multiple-exchange algorithm based on the extended theorem is presented for designing linear-phase FIR filters with frequency mixed constraints in the minimax sense. Further, convergence of the algorithm is established. Several design examples and comparisons with existing techniques are presented, and the simulation results show that the proposed algorithm is numerically more efficient and guaranteed to converge to the optimal solution.     

Switched-Current Filters Revisited: Square-Root Domain Sampled-Data Filters

In this brief, the well-known switched-current (SI) filtering technique is revisited using the concept of the square-root domain (SRD) filtering. It is proved that SI filters are a subclass of the SRD filters, where sampled-data signal processing is performed. This is achieved by considering typical lossless and lossy SRD sampled-data integrator configurations, using a set of complementary SRD operators which are based on the quadratic I-V relationship of MOS transistor operated in the saturation. Circuit examples are given, where linear-domain integrator and third-order filter configurations were derived using appropriate SRD sampled-data building blocks     

滤波器的测试

像传输线那样,可以测试任何一种滤波器或陷波器的阻抗和频率响应。滤波器在其带宽内应该具有等于输入激励源阻抗和负载阻抗的输入阻抗和输出阻抗。为了测试阻抗,可以进行开路测试和短路测试。为了更加了解这种测试,请考虑图2.43滤波器或传输线的电路图。该电路图为平衡     

太赫兹滤波器

太赫兹技术在生物、国防以及基础研究等方面有重要的应用,要实现对太赫兹波技术的实际有效的应用,与之相关的太赫兹传导、滤波器件等功能器件至关重要.目前太赫兹滤波器结构主要基于二维光子晶体、超颖材料、表面等离子体等结构.就太赫兹滤波器的研究进展进行了总结,并对其今后的研究发展方向进行了分析.