High-Q HF microelectromechanical filters

IC-compatible microelectromechanical intermediate frequency filters using integrated resonators with Q's in the thousands to achieve filter Q's in the hundreds have been demonstrated using a polysilicon surface micromachining technology. These filters are composed of two clamped-clamped beam micromechanical resonators coupled by a soft flexural-mode mechanical spring. The center frequency of a given filter is determined by the resonance frequency of the constituent resonators, while the bandwidth is determined by the coupling spring dimensions and its location between the resonators. Quarter-wavelength coupling is required on this microscale to alleviate mass loading effects caused by similar resonator and coupler dimensions. Despite constraints arising from quarter-wavelength design, a range of percent bandwidths is still attainable by taking advantage of low-velocity spring attachment locations. A complete design procedure is presented in which electromechanical analogies are used to model the mechanical device via equivalent electrical circuits. Filter center frequencies around 8 MHz with Q's from 40 to 450 (i.e., percent bandwidths from 0.23 to 2.5%), associated insertion losses less than 2 dB, and spurious-free dynamic ranges around 78 dB are demonstrated using low-velocity designs with input and output termination resistances of the order of 12 kΩ     

Coplanar stripline resonators modeling and applications to filters

This paper presents coplanar stripline (CPS) resonators and their practical implementations to filters. Five types of CPS resonator are built using open and short-ended strips. Lumped-element equivalent circuits are presented for each resonator. Their performances are investigated and compared in terms of Q factor or bandwidth. Two types of bandpass filter are developed with the resonators. The bandpass filters have low-passband insertion losses and wide-stopband suppression bandwidths. Lumped-element equivalent circuits are presented for the bandpass filters. A wide-band CPS-to-microstrip transition is developed for the measurements. The back-to-back transition has an insertion loss of less than 3 dB and a return loss of better than 10 dB for the frequency range from 1.3 to 13.3 GHz (1:10.2)     

Applications of layer-by-layer polymer stereolithography for three-dimensional high-frequency components

A laser-based layer-by-layer additive process, stereolithography, is used to create truly three-dimensional (3-D) structures for high-frequency applications. High aspect-ratio complicated 3-D structures embedded inside of a layer-by-layer package are created by this process. Previously, Q's greater than 3000 and tolerances of /spl sim/0.19% have been achieved for embedded resonators. In this paper, more applications are demonstrated. Particular examples include the integration of a nonplanar monopole antenna coupled to a high-Q embedded cavity with only 0.26% shift in resonant frequency (19.37 GHz) and a slight 0.06% reduction in bandwidth compared to simulation. Stacked cavities and coupling sections within a substrate are also demonstrated to create vertically integrated filters. For 2% bandwidth two-pole filters, insertion losses as small as 0.27 dB are measured. Furthermore, a vertically integrated 1.2% four-pole filter is demonstrated with acceptable performance without tuning after fabrication. These applications illustrate that the laser-based stereolithography process is suitable for the integration of high-frequency and high-Q 3-D structures within a package.     

Miniaturized hairpin resonator filters and their application toreceiver front-end MICs

The authors describe the fundamental characteristics of miniaturized hairpin resonators having parallel coupled lines and show their applications to bandpass filters and receiver front-end microwave integrated circuits (MICs). A method for calculating filter coupling parameters using a general-purpose microwave circuit simulator is presented. The bandpass filters have a suitable structure for MICs, and their size is one-half that of conventional hairpin resonators without increasing insertion losses. Trial receiver front-end MICs using these filters have been developed and have shown good characteristics such as low noise and a high image suppression ratio. They are applicable to a frequency range above the L-band     

Loop-Gap Resonator: A Lumped Mode Microwave Resonant Structure

Loop-gap resonators are newly developed microwave resonant structures with a field configuration that is intermediate between lumped and distributed. Typical characteristic dimensions are of the order of 1/10 of the resonant wavelength, and typical Q's are of the order of 1600-2000 in the frequency range of 1-4 GHz. Data are presented for Q's and frequencies for a series of resonators of various dimensions and compared with theory. Various coupling and frequency tuning techniques are discussed, and results of experiments are reported. Results of preliminary application of the stictire in microwave filters and oscillators are presented. Loop-gap resonators provide a useful design alternative, it is concluded, to dielectric and surface acoustic-wave resonators at low microwave frequencies.     

High Tc superconducting three-pole parallel-coupled bandpass filters made from laser ablated YBa2Cu3O7 − δ thin films

We have investigated three-pole parallel-coupled bandpass filters with fractional bandwidths of about 6% and 3% at a center frequency of 10.5 GHz utilizing high T_c superconducting YBa₂Cu₃O_{7 − δ} thin films. The films were deposited on LaAlO₃ substrates by pulsed laser ablation. Microwave responses of the filters were measured as a function of temperature and input power. The performance of the 3% bandwidth filter exhibits low insertion losses of about 0.48 dB and 0.79 dB at 20 K and 77 K, respectively. The insertion loss in the 6% bandwidth filter was 0.96 dB at 77 K. Both filters showed return losses better than 15 dB. High T_c superconducting bandpass filters showed good reproducibility. They were also compared with equivalent gold filters which showed insertion losses of more than 8 dB at 77 K.     

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.     

基于扇形基片集成波导的三频带通滤波器设计

该文提出了一种60°扇形基片集成波导谐振器,然后在谐振器中加载一排金属通孔,对其TM₁₁₀、TM₂₁₀和TM₁₂₀模进行扰动,最后利用扰动后的场模式,在60°扇形基片集成波导谐振器的基础上设计了一款结构紧凑的三频带通滤波器。通过分别引入互补开口环谐振器和源-负载耦合结构,改善了滤波器的频率选择特性。3个通带的中心频率分别为5.61 GHz、7.41 GHz和8.77 GHz,3 dB带宽分别为148 MHz、298 MHz、347 MHz。滤波器的测试与仿真结果基本吻合。     

Slot-fed higher order mode Fabry-Perot filters

Low-loss bandpass filters consisting of Fabry-Perot resonators excited by waveguide-fed slots coupling to higher-order resonator modes are demonstrated. For close reflector spacings, the waveguide couples efficiently through the slots to the TEM₄₀₀ and TEM₃₀₀ modes. The characteristics of both rectangular and circular waveguide feeds with various slot lengths and widths are presented. At X-band the filters have unloaded Q values which range from 1000 to 7000 with insertion losses less than 1 dB. The filters which have the rectangular waveguide feeds are mechanically tunable over a 20% bandwidth     

Design and applications of two-port SAW resonators on YZ-lithium niobate

The fundamental design criteria for two-port SAW resonators are discussed. The distributed reflective arrays are modeled as lossy repetitively mismatched transmission lines with impedance mismatch ε and expressions for the reflection magnitude and phase are given. An experimental technique is described to directly determine both ε and the proper placement of the input/output transducers. Experimental two-port resonator filters have been realized having Q's of 2000-5000, 5-7 dB insertion loss, and ∼35-dB sidelobe suppression. By electrically cascading three resonators, sidelobe suppression of ∼80 dB has been achieved. Resonator structures have been developed in which continuous frequency tuning up to 0.18 percent has been obtained by electronic means.     

Dual and tri-band bandpass filters based on novel Π-shaped resonator

A novel Π-shaped resonator is proposed, and compact dual-band and tri-band bandpass filters that meet IEEE 802.11 application requirements by using the new resonator are designed. The dual-band bandpass filter centres at 2.45 and 5.6 GHz with a simulated passband insertion loss of no more than 0.8 dB, and the tri-band bandpass filter which is got by two-path coupling achieves simulated passband insertion loss of no more than 1.1 dB. The new designs are demonstrated by experiment. The new filters have advantages of simple and compact structures, low passband insertion losses, good frequency selectivity and miniature circuit sizes. All these have prospect to be applied in future wireless communication systems.     

L,S波段高性能窄带有源滤波器的研制

本文研究了一种直接利用晶体管或场效应管来模拟高Ｑ值电感，并利用此电感来制作Ｌ波段和Ｓ波段窄带有源滤波器的方法。利用此方法制作了两个高性能的窄带有源带通滤波器：一个中心频率为２．３ＧＨｚ，其带宽为９０ＭＨｚ左右，带内插入损耗为０ｄＢ；一个中心频率在１．５ＧＨｚ左右，并且中心频率可调，其带宽为８０ＭＨｚ左右，带内有１０ｄＢ的增益     

Conductor-loss limited stripline resonator and filters

We report on stripline resonators on thin dielectric membranes that show dispersion-free, conductor-loss limited performance at 13.5 GHz, 27.3 GHz, and 39.6 GHz. The unloaded-Q (Q_u) of the resonators increases as √f with frequency and is measured to be 386 at 27 GHz. The measured results agree well with a new conformal mapping analysis. The stripline resonators are used in a micromachined state-of-the-art planar interdigitated bandpass filter at K-band frequencies. Excellent agreement has been achieved between the microwave model at 850 MHz and the 20 GHz filter. The micromachined filter exhibits a passband return loss better than -15 dB and a conductor-loss limited 1.7 dB port-to-port insertion loss (including input/output CPW line loss) at 20.3 GHz     

Adjustable multilayer HTS filters

An adjustable multilayer high-temperature superconductor (HTS) bandpass filter has been fabricated. Taped comb-line filters with multilayer structures were designed, YBa₂Cu₃O_7-δ (YBCO) thin films deposited on LaAlO₃ were used to construct the packaged multilayer HTS filter. The electrical length of the resonators in the filter was smaller than a quarter-wave length. The frequency responses of the filter were measured at liquid nitrogen temperature 77 K. The insertion loss of the packaged filter was determined to be less than 0.5 dB. By mechanically adjusting the multilayer structure, the center frequencies of the filter changed from 1.78 to 1.92 GHz, and the variations of the bandwidth from 60 to 150 MHz were also obtained     

960 MHz同轴介质谐振器滤波器的研制

研制了用四个高Q值介质同轴谐振器构成的带通滤波器,谐振器之间的耦合通过陶瓷基片上的电容实现,讨论了影响谐振器插入损耗的主要因素。结果表明,该四级式低损耗介质同轴谐振器滤波器中心频率f0为960MHz,插入损耗小于3.0dB,能满足设计要求。     

Filter response of single-mode fibre recirculating delay lines

Single-mode fibre recirculating delay lines have been made on a single continuous loop of fibre with the use of fibre directional couplers. These devices have been demonstrated as bandpass filters and as notch filters at centre frequencies from 0.5 MHz to 1.3 GHz with a notch depth of over 45 dB.     

基于齿状缺陷地的宽阻带交叉耦合SIW滤波器

提出了一种齿状缺陷地低通传输线结构,该低通传输线由多级齿状缺陷地构成,通过调节齿状缺陷地枝节长度,可以有效调节低通和阻带频率范围。利用该齿状缺陷地结构,级联交叉耦合扇形基片集成波导(SIW)滤波器,该文设计了一款高带外抑制的宽阻带滤波器,与传统SIW带通滤波器相比,其矩形系数K_{40 dB}=2,阻带范围大于2倍的中心频率,具有较好的通带和阻带选择特性。测试结果表明,滤波器的中心频率为10.35 GHz,3 dB和40 dB带宽分别为507 MHz和1.05 GHz,插入损耗优于1.47 dB,与仿真结果基本一致。     

Precision fabrication techniques and analysis on high-Q evanescent-mode resonators and filters of different geometries

High-Q evanescent-mode resonators and filters are realized by both silicon micromachining and layer-by-layer polymer processing. Capacitively loaded cavities can be reduced to a size much smaller than a wavelength, but still have a much higher unloaded Q than lumped elements. The loaded resonators are utilized for reduced-size filters with a low insertion loss enabled by the relatively high-Q factor. The small fabrication tolerances of silicon micromachining and polymer stereolithography processing enable the realization of highly loaded evanescent-mode resonators and filters. A 14-GHz resonator micromachined in silicon has a volume of 5 mm /spl times/ 5 mm /spl times/ 0.45 mm, representing a resonant frequency reduction of 66.8% compared to an empty cavity of the same dimensions. The polymer-based fabrication is used to create resonators of different three-dimensional geometries with Q's up to 1940 and frequency reductions up to 49.9%. An insertion loss of 0.83 dB is measured in a 1.69% bandwidth filter created by polymer processing with a frequency reduction of 47% compared to an unloaded cavity. The frequency sensitivity to fabrication tolerances of these structures is also analyzed.     

Multilayer resonators and a bandpass filter fabricated from a novel low-temperature co-fired ceramic

The main objective of this study was to make components from a novel low-loss, low-temperature Co-fired ceramic (LTCC) dielectric, which was also compatible with a high-conductivity silver paste. The multilayer-component fabrication procedure is presented together with a composition for a tape-casting slurry, choice of conductor paste, and LTCC process parameters. A good Q factor, >100 at 2 GHz, using the novel material system has been achieved for λ/2 resonators operating in the frequency range 1.7–3.7 GHz. An excellent frequency response for a 2 GHz bandpass filter has also been achieved; the insertion losses in the passband were less than −2 dB (bandwidth 60 MHz) and the attenuation more than 25 dB in the stopband located 190 MHz higher.     

Novel Dual-Mode Dual-Band Filters Using Coplanar-Waveguide-Fed Ring Resonators

This paper presents a novel approach for designing dual-mode dual-band bandpass filters with independently controlled center frequencies and bandwidths. Two microstrip perturbed ring resonators are employed to obtain dual-mode dual-band responses. Novel feeding structures are introduced to simultaneously feed the ring resonators and conveniently control the coupling strength between resonators and feeding lines, resulting in a wide tunable range of external quality factors. Two kinds of filter configurations with compact size are proposed. Both of them provide sufficient degrees of freedom to satisfy various requirements of external qualify factors and coupling coefficients at both passbands. Therefore, the center frequencies and fractional bandwidths of both passbands can be independently tuned to desired specifications within a wide range. To verify the proposed method, four filters are implemented. The measured results exhibit dual-mode dual-band bandpass responses with high selectivity.