变容管电调微波带通滤波器

本文叙述采用梳状线结构的变容管电调微波带通滤波器的设计理论和方法。推导出梳状线带通滤波器的输入、输出耦合网络的参数条件,以补偿带通滤波器的谐振器之间电磁耦合随不同调谐频率的变化;并给出使带通滤波器的绝对带宽或通带回波损耗在调谐频率范围内变化最小时,梳状线谐振器的电长度应满足的相应条件,由此来保证电调带通滤波器在较宽的调谐频率范围内具有较高的通带回波损耗,且保持带通滤波器的响应形状和绝对带宽基本不变。此外,还讨论了由电调变容管的Q值引起的带通滤波器的通带有功损耗问题。文中给出了具体的设计公式。最后,给出了一个L波段变容管电调带通滤波器的研制实例和测试结果。     

一种双频电调带通滤波器的设计

提出一种新型中心频率可调谐的双频带通滤波器,该滤波器利用双端短路的阶梯阻抗谐振器(stepped-impedance resonator,SIR)结构,在其中两个不同特性阻抗传输线之间同时加载变容二极管,其输入输出结构采用50Ω的缝隙耦合馈电。采用半波长SIR的折叠型结构,实现了滤波器的小型化。并通过奇偶模的分析方法,调节变容二极管上加载的电压实现中心频率分别在1.97~2.20 GHz和4.15~4.30 GHz之间可调。比较仿真与测量结果证明了该方法有效。     

LC电调带通滤波器的设计

本文采用桥接网络法设计了一个LC电调带通滤波器,1dB通带连续可调范围为：110～125MHz至110～155MHz、体积为25mm×13mm×7mm。对桥接网络法的椭圆类型滤波器做了深一层研究,找到了提高其矩形系数及带外抑制的改进方法。     

电调梳状带通滤波器的设计

本文设计了一种能够在特高频（UHF）工作的可电调梳状微带线带通滤波器,可通过调节加在变容二极管两 端的电压值实现滤波器工作频率的改变,可调工作频段为500MHz-1000MHz,电压调节范围为1-13V。具有带宽小、 阻带抑制高、结构小型化、易程控迅速精确切换频率以及加工一致性较好等特点。文中还就变容二极管选取、建模以 及一些敏感的参数等做了讨论。     

微波电调带通滤波器的研究

介绍了几种典型的微波电调滤波电路设计方法。经研究设计并制作了一相对带宽小于２％的电调通滤波器。改进型谐振器设计使该电路具有温度性能好,制作简单、可靠性高等优点,并对该种电路进行了全波分析。     

带宽恒定的电调带通滤波器

为了减小电调带通滤波器结构的复杂度,该文设计了一种基于阶梯阻抗谐振器的电调滤波器。以变容二极管作为电调元件,贴片电感作为输入、输出耦合元件。采用ADS和HFSS软件分析了耦合系数和外部品质因数随频率的变化关系。仿真结果表明,在0.45～1.0 GHz,耦合系数和外部品质因数保持恒定。采用相对介电常数为2.2的Rogers 5880 (tm)介质基板制作实物,并用网络分析仪进行测试,实测结果与仿真结果基本一致。     

微波电调带通滤波器的研究

介绍了几种典型的微波电调滤波电路设计方法。经研究设计并制作了一相对带宽小于２％的电调带通滤波器。改进型谐振器设计使该电路具有温度性能好、制作简单、可靠性高等优点,并对该种电路进行了全波分析。     

数控电调带通滤波器的设计与制作

设计了一种新型电调谐带通滤波器,研究了数字信号控制滤波器电调谐的技术。采用数模转换器和高压运放实现数字信号与直流电压的转换;以变容二极管作为调谐元件;带通滤波器采用梳状微带线结构,并给出了结构参数。最后制作了一个由8位二进制编码控制的电调谐带通滤波器,其中心频率在300～1200MHz可调。测试结果与理论设计基本吻合。     

可重构滤波器研究进展综述

随着通信、雷达等无线电系统向高频、宽带和小型化方向发展,出现了多种形式的可重构微波滤波器。本文综述了各种典型可重构滤波器的发展现状,对比分析了不同种类可重构滤波器的优缺点。得出的结论是:在毫米波频段,基于液晶和铁氧体等新材料的可重构滤波器具有低损耗的优势,而基于MEMS技术的可重构滤波器兼具适应高频段和易于集成的优点,这将是未来可重构滤波器研究的重要方向。     

Two-branch microwave channelized active bandpass filters

The realization of small highly selective microwave filters has emerged as a prominent issue in the design of miniaturized high-frequency systems. In this paper, a new way to implement channelized active bandpass filters is presented that deals with the impasse. The concept involves a two-branch configuration, which yields filter circuits that are more compact and offer lower noise figures than earlier three-branch versions, while still retaining all the advantages of channelized feedforward operation. The practicability of the technique is demonstrated with two 10 GHz bandpass filters of different design, whose assessed performance characteristics include signal distortion and noise properties     

Low-loss and compact V-band MEMS-based analog tunable bandpass filters

This paper presents compact V-band MEMS-based analog tunable bandpass filters with improved tuning ranges and low losses. For compact size and wide tuning range, the two-pole filters are designed using the lumped-elements topology with metal-air-metal (MAM) bridge-type capacitors as tuning elements. Capacitive inter-resonator coupling has been employed to minimize the radiation loss, which is the main loss contributor at high frequencies. Two filters have been demonstrated at 50 and 65 GHz. The 65-GHz analog tunable filter showed a frequency tuning bandwidth of 10% (6.5 GHz) with low and flat insertion losses of 3.3 /spl plusmn/ 0.2 dB over the entire tuning range.     

Progress of a tunable active bandpass filter

A review of a tunable active bandpass filter developed in our research group is given here. Presented first is the basic structure of an end-coupled microstrip-line bandpass filter. Next discussed is the concept of using coupled negative resistance to compensate the loss of tank circuit. Then, the method of using varactor diode or mesfet varactor to tune the center frequency of the passband is discussed. The capability of optical-control of mesfet varactor and the concept of using mesfets as three-terminal varactors are also discussed.     

Large-area varactor diode for electrically tunable, high-power UHF bandpass filter

An electronically tunable, high-power, UHF (225-400-MHz) bandpass filter which utilizes large-area, high-capacitance varactor diodes has been designed and tested. The varactor diodes with 100-V breakdown potential, uniform impurity density in the active layer and 400-pF capacitance at -8-V bias are used as the tuning elements of the filter. The diodes are fabricated from epitaxial layers grown on high-conductivity silicon substrates. The epitaxial layers include an n⁺transition layer between the substrate and n-type active layer to minimize the growth defects in the n layer which reduce the breakdown potential to a fraction of the theoretical value. Measurements in a test cavity at 151 MHz indicate a diode Q of 190 at -8-V bias. Input power levels of 1-5 W can be accommodated across the tuning range. Insertion loss varies from 4 to 7 dB and intermodulation products are suppressed 30 dB or more for two input tones of 1 W each. This filter exhibits an order-of-magnitude improvement in power-handling capability over present state-of-the-art filters.     

Quality of ferroelectric capacitors used in tunable microwave filters

The problem of determining the quality of ferroelectric capacitors from measured characteristics of tunable microwave bandpass filters has been solved. The quality of ferroelectric capacitors based on barium-strontium-titanate (BST) thin films, used in four filters tunable over a frequency range of 1.8 to 4.3 GHz, have been determined.     

High-performance microwave coplanar bandpass and bandstop filters on Si substrates

High-performance bandpass and bandstop microwave coplanar filters, which operate from 22 to 91 GHz, have been fabricated on Si substrates. This was achieved using an optimized proton implantation process that converts the standard low-resistivity (/spl sim/10 /spl Omega//spl middot/cm) Si to a semi-insulating state. The bandpass filters consist of coupled lines to form a series resonator, while the bandstop filter was designed in a double-folded short-end stub structure. For the bandpass filters at 40 and 91 GHz, low insertion loss was measured, close to electromagnetic simulation values. We also fabricated excellent bandstop filters with very low transmission loss of /spl sim/1 dB and deep band rejection at both 22 and 50 GHz. The good filter performance was confirmed by the higher substrate impedance to ground, which was extracted from the well-matched S-parameter equivalent-circuit data.