Novel Broadside-Coupled Bandpass Filters Using Both Microstrip and Coplanar-Waveguide Resonators

Novel quasi-elliptic coupled-resonator bandpass filters with wider fractional bandwidth are proposed. By using the broadside-coupled mechanism to couple the half-wavelength microstrip resonators and the quarter-wavelength coplanar-waveguide (CPW) resonators together with introducing two CPW shorted stubs, the required mixed and magnetic couplings associated with the resonators may be enhanced so that a wider bandwidth cross-coupled filter may be realized. Specifically, a fourth-order quasi-elliptic broadside-coupled bandpass filter with a center frequency at$f _0 =1.48~hboxGHz$, a minimum insertion loss of 0.68 dB, and a wider 3-dB fractional bandwidth of 34.6% is implemented, and its stopband is extended up to 6 GHz$(4f _0)$with a rejection better than 20 dB.     

UHF Band Ultra-Narrowband Superconducting Filter With Double U-Type Secondary Coupling Structure

A double U-type secondary coupling structure (DUSCS) is used for a compact ultra-narrowband filter in the ultra-high frequency (UHF) band. It can effectively reduce the coupling and thus spacing between coupled twin-spiral resonators. A six-pole superconducting filter at 600 MHz with a fractional bandwidth of 0.083% is designed and fabricated to validate this technique. The filter size is reduced by 15% compared with the filter designed without DUSCSs.      

Tunable combline filter with continuous control of center frequency and bandwidth

A new combline filter structure with a continuous tunability for both the center frequency and bandwidth is presented in this paper. The passband-width tunability is achieved by placing variable coupling reducers between the filter resonators. The coupling reducers, operating as bandwidth control subnetworks, are designed as detuned resonators made up of a line segment ending in a variable capacitor. The proposed filter structure is experimentally validated with the design, construction in suspended stripline technology, and characterization of a low-cost filter prototype for terrestrial digital video broadcasting receivers operating in the UHF band (470-862 MHz). Other relevant factors, such as the intermodulation distortion produced by the varactors used to control the bandwidth electronically or the power-handling performance of the constructed filter, are also discussed. The reconfigurable filter module described in this paper is very suitable for the design of flexible multifunction receiver subsystems simultaneously supporting signals with a different bandwidth.     

Low-Loss 5.15–5.70-GHz RF MEMS Switchable Filter for Wireless LAN Applications

Low-loss 3.6-GHz fixed and 5.15-5.70-GHz RF microelectromechanical systems switchable filters were designed and fabricated on quartz substrates. Detailed design equations for the capacitively loaded coupled open-loop lambda/2 resonators are given and the realization of the tunable filter using these equations is discussed. The use of capacitively loaded coupled open-loop lambda/2 resonators made it possible to realize the fixed and switchable filters with unloaded Q of around 150 resulting in a -1.4-dB insertion loss. The measured -1-dB bandwidth for the 3.6-GHz fixed and 5.15-5.70-GHz switchable filters were 4% and 5%, respectively. To our knowledge, this represents the lowest loss planar tunable filter to-date in the 4-6-GHz frequency range     

阶梯阻抗谐振器在微波双通带滤波器设计中的应用

阶梯阻抗谐振器（Stepped Impedance Resonator）寄生响应的位置可以通过调整谐振器阻抗比来控制,该特性使SIR成为设计双通带滤波器的理想谐振器。设计耦合谐振器双通带滤波器需要对两组外部品质因数和耦合系数进行综合,为了减少谐振器的数量同时简化耦合系数的提取,本文采用特定耦合结构设计滤波器,并研究了影响SIR主响应和第一寄生响应处外部品质因数的因素,设计了中心频率是1.9GHz和3.2GHz,部分带宽是5%和7%的双通带滤波器。仿真结果验证了设计方法的可行性。     

C-Band Multilayer Bandpass Filter Using Open-Loop Resonators With Floating Metallic Patches

This letter presents a fourth-order quasi elliptic bandpass filter based on a multilayer technology. Thanks to the use of the third dimension, multilayer technology appears as a very convenient solution when a high coupling is required. This led us to use a coupling coefficient-based approach to design a very compact filter through the association of open-loop resonators and floating metallic patches to elevate coupling.     

Development of new miniaturised bandpass filter having ultrawidebandwidth

A new, compact, very-broadband bandpass filter, consisting of two-parallel-conductor short-circuited spurline resonators, quarter-wavelength long, is described. Approximate design formulas for the filter are derived. The chain matrix of the resonators is also obtained and used in predicting the filter response. It is found that this filter possesses a very wide bandwidth, more than 5:1. A microstrip filter having a passband from 1.8 to 9.2 GHz has been designed and tested with less than 1 dB insertion loss. There is also a reasonably good agreement between the experimental and theoretical performances. The developed filter is very attractive for wideband microwave integrated circuits due to its compactness and very wide bandwidth     

Couplings of microstrip square open-loop resonators forcross-coupled planar microwave filters

A new type of cross-coupled planar microwave filter using coupled microstrip square open-loop resonators is proposed. A method for the rigorous calculation of the coupling coefficients of three basic coupling structures encountered in this type of filter is developed. Simple empirical models are derived for estimation of the coupling coefficients. Experiments are performed to verify the theory. A four-pole elliptic function filter of this type is designed and fabricated. Both the theoretical and experimental performance is presented     

A compact open-loop resonator filter with a wide stopband response

This paper presents a new class of microstrip slow-wave open-loop resonator filter with reduced size and improved stopband characteristics. A comprehensive treatment of both resonator ends loaded with triangular and rectangular shapes is described, leading to the invention of a microstrip slow-wave open-loop resonator. A four-resonator bandpass filter is designed at the operating frequency about 2 GHz, bandwidth of 60 MHz. The size of the slow-wave open-loop resonator is optimized from the standpoint of the unloaded Q-factor. The proposed filter is not only compact size due to the slow-wave effect but also has a wider upper stopband resulting from the dispersion effect. The filter design of this type will be described in detail. The experimental results are demonstrated and discussed.     

广义耦合矩阵在多工器设计中的应用

介绍一种新型的适用于耦合谐振器网络的多端口耦合矩阵,它是对过去的双端口网络耦合矩阵的推广。应用多端口网络耦合矩阵可以方便地优化综合多工器,这样得到的多工器由于没有额外的消抗网络,相比过去的设计方案要小型而紧凑得多。通过仿真试验,验证了其有效性,及与理论的一致性。     

Higher order optical resonant filters based on coupled defect resonators in photonic crystals

In this paper, a general methodology for the design of higher order coupled resonator filters in photonic crystals (PCs) is presented. In the proposed approach, the coupling between resonators is treated as though it occurs through a waveguide with an arbitrary phase shift. The coupling through the waveguide is analyzed theoretically, based on the coupled-mode theory in time. The derived theoretical model suggests a way to extend an equivalent circuit approach, previously demonstrated with a certain value of a phase shift, to the higher order filter design with an arbitrary phase shift. The validity of the proposed approach is confirmed by the design of a third-order Chebyshev filter having a center frequency of 193.55 THz, a flat bandwidth of 50 GHz, and ripples of 0.3 dB in the passband. The characteristics of the designed filter are suitable for wavelength-division-multiplexed (WDM) optical communication systems with a 100-GHz channel spacing. The performance of the designed filter is numerically calculated using the two-dimensional (2-D) finite-difference time-domain (FDTD) method.     

A Low Loss X-Band Quasi-Elliptic Ferroelectric Tunable Filter

A compact high quality factor four-pole X-band tunable quasi-elliptic bandpass filter is presented in this letter. The filter is enabled by high-Q ferroelectric barium strontium titanate capacitors and open-loop resonators. The central frequency of 8.35 GHz and the frequency tuning range of 500 MHz (6%) are achieved with a dc bias voltage of 30 V. The selective filter has a fractional 1 dB bandwidth ranging from 5.5% up to 7.3%. The measured insertion loss and return loss are 5.7-3.5 dB and 10.2-7.9 dB, respectively, with a dc bias range of 0 to 30 V. To the best of our knowledge, this is the best analog tunable performance and selectivity in X-band.     

基于枝节线加载谐振器的可调滤波器设计

传统基于变容二极管的双频电可调滤波器由于外部容值的加入,该类滤波器的插损变大,同时相对带宽锐减。基于多模谐振器结构,提出了一种新型的工作频段独立、电可调的双频带通滤波器。该滤波器由短路枝节线加载谐振器和一对1/4 波长谐振器组成。在各自的谐振器末端加载带有变容二极管的外部偏置电路,1/4 波长谐振器构成第一通带,短路枝节线加载谐振器构成第二通带,两通带之间互不干扰,单独调节。应用奇偶模分析法及调节耦合间距的方法,确保双通带均出现两个极点,保证其带宽的稳定性。该电可调滤波器第一通带可调范围为0.7 ~0.85 GHz,第二通带可调范围为0.9 ~1.05 GHz,同时双频带的相对带宽基本保持在10% 以上,较以往的双频电可调滤波器,该款滤波器的相对带宽有了较为明显的提升。     

Waveguide bandpass filter with easily adjustable transmission zeros and 3-dB bandwidth

This paper presents a compact waveguide bandpass filter with adjustable transmission zeros (TZs) and bandwidth. The design provides the flexibility to place the TZs at the desired locations for better interference rejection. To demonstrate, initially a three-pole bandpass filter has been designed by placing three single slot resonator structures inside a WR-90 waveguide. Next, two additional asymmetrical slot structures have been used with each of the above resonators to generate two TZs, one on each side of the passband. Since three resonators were used, this process results in six asymmetric slot structures those results in six TZs. The final filter operates at 9.98 GHz with a 3-dB bandwidth of 1.02 GHz and TZs at 8.23/8.70/9.16/10.9/11.6 and 13.115 GHz. Equivalent circuits and necessary design equations have been provided. To validate the simulation, the proposed filter has been fabricated and measured. The measured data show good agreement with simulated data.     

基于双模开环谐振器的双频带滤波器设计

基于开环双模谐振器设计了一种双频带通滤波器,由两个中心重合的正方形开口环谐振器组成。分析该谐振器的奇偶模谐振频率与传输零点,每个通带内有两个谐振模式。该滤波器中心频率分别为4.5 GHz和6.5 GHz,3 dB相对带宽FBW分别为11%、5%,两通带带内插入损耗分别小于0.6 dB、1.4 dB,带内回波损耗分别优于19.5 dB、16.5 dB,高频处阻带抑制达到50 dB,两通带之间隔离度达到53 dB,尺寸仅为6 mm×11 mm×1.09 mm。     

一种具有边带陡峭特性的超窄带滤波器

应用LTCC技术,设计了一款带通滤波器。采用开口环谐振结构作为基本谐振单元,利用谐振级之间的耦合产生传输零点,实现边带抑制。给出了开口环谐振结构的等效电路分析,滤波器的通带中心频率为23.2 GHz,3-dB带宽为600 MHz,具有很窄的相对带宽,3-dB相对带宽仅为2.6%。对滤波器进行仿真和优化,结果表明,通带22.9~23.5 GHz内插损小于3 dB,低阻带10~21.1 GHz的衰减大于45 dB,高阻带25.3~40 GHz的衰减均大于30 dB。该滤波器的尺寸为4 mm×3.5 mm×0.45 mm,具有非常好的窄带特性和边带抑制特性。     

Synthesis of prototype filters with triplet sections starting fromsource and load

Describes a method for synthesizing an inline prototype filter with a triplet section starting from source and/or from load. This topology allows placing one or two transmission zeros without using cross-couplings inside the filter (it is only required to couple the source (or the load) to the first (or the last) two resonators). The proposed method employs the coupling matrix of a generic prototype, obtained through well-established procedures; then, the coupling matrix of the desired inline topology is determined with a procedure based on multiple matrix rotations (similarity transforms) and numerical optimization     

基于DGS结构的超宽带带通滤波器

基于双开口-互补开环谐振器的缺陷地结构(DGS),设计了一个结构紧凑的基片集成波导(SIW)超宽带带通滤波器。通过调整蚀刻在SIW底面的双开口-互补开环谐振器,SIW表面的共面波导与腔体之间的耦合,同时在阻带获得3个传输零点,以得到较好的频率选择性和良好的带外抑制。经过仿真优化及实物制作,测试结果表明,该滤波器工作在7.2GHz,相对带宽28%,带外抑制良好,仿真与测试结果吻合。     

Design of a wide-band lumped-element 3-dB quadrature coupler

Analysis and design techniques for designing a lumped-element 3-dB quadrature coupler with wide-band flat coupling are proposed for microwave integrated-circuit/monolithic-microwave integrated-circuit applications. The proposed design technique can produce a coupler with flat coupling over 50% fractional bandwidth, which is wider than the conventional lumped-element design methods. A prototype consisting of a capacitive coupled high-pass network is designed and fabricated to verify the design concept. Measurement and simulation results closely correspond to each other     

Frequency-selective properties of a microstrip filter with irregular dual-mode resonators

Frequency-selective properties of a microstrip filter containing dual-mode hairpin resonators with a stepwise change in the width of the stripline conductor whose one end is connected to the screen are studied. Dependences of the design parameters and the steepness of the slopes of the amplitude-frequency response of a two-resonator filter on the filter fractional bandwidth and the substrate permittivity are considered. A large domain of the anomalous behavior of the gaps between the resonator conductors, in which the gap increases with the width of the filter passband, is revealed. The domain of values of the fractional bandwidth and the frequency band in which the design parameters of the device are realizable are determined. Good agreement between the results of the quasi-static calculation and experimental results is demonstrated.